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Synthetic and artificial fiber
Image by Joost J. Bakker IJmuiden
Synthetic and artificial fiber
Synthetic fibers are the result of extensive research by scientists to improve on naturally occurring animal and plant fibers. In general, synthetic fibers are created by forcing, usually through extrusion, fiber forming materials through holes (called spinnerets) into the air, forming a thread. Before synthetic fibers were developed, artificially manufactured fibers were made from cellulose, which comes from plants. These fibers are called cellulose fibers.
Synthetic fibers account for about half of all fiber usage, with applications in every field of fiber and textile technology. Although many classes of fiber based on synthetic polymers have been evaluated as potentially valuable commercial products, four of them - nylon, polyester, acrylic and polyolefin - dominate the market. These four account for approximately 98 per cent by volume of synthetic fiber production, with polyester alone accounting for around 60 per cent.
HistoryThe first artificial fiber, known as artificial silk, became known as viscose around 1894, and finally rayon in 1924. A similar product known as cellulose acetate was discovered in 1865. Rayon and acetate are both artificial fibers, but not truly synthetic, being made from wood. Although these artificial fibers were discovered in the mid-nineteenth century, successful modern manufacture began much later (see the dates below).
Nylon, the first synthetic fiber, made its debut in the United States as a replacement for silk, just in time for World War II rationing. Its novel use as a material for women's stockings overshadowed more practical uses, such as a replacement for the silk in parachutes and other military uses.
Common synthetic fibers include:
Rayon (1910) (artificial, not synthetic)
Acetate (1924) (artificial, not synthetic)
Nylon (1939)
Modacrylic (1949)
Olefin (1949)
Acrylic (1950)
Rayon
Rayon is a manufactured regenerated cellulose fiber. Because it is produced from naturally occurring polymers, it is neither a truly synthetic fiber nor a natural fiber; it is a semi-synthetic or artificial fiber. Rayon is known by the names viscose rayon and art silk in the textile industry. It usually has a high luster quality giving it a bright sheen.
Uses
Some major rayon fiber uses include apparel (e.g. blouses, dresses, jackets, lingerie, linings, scarves, suits, neckties, hats, socks), the filling in Zippo lighters, furnishings (e.g. bedspreads, bedsheets, blankets, window treatments, upholstery, slipcovers), industrial uses (e.g. medical surgery products, non-woven products, tire cord), and other uses (e.g. yarn, feminine hygiene products, diapers, towels). Rayon is a major feedstock in the production of carbon fiber.
In early 2010, the U.S. Federal Trade Commission warned several retailers that six major manufacturers were falsely labeling rayon products as "bamboo", in order to appeal to environmentally conscious consumers. While rayon may be produced with bamboo as a raw material, and the two may be used for similar fabrics (though natural bamboo is not as smooth), rayon is so far removed from bamboo by chemical processing that the two are entirely separate.
History
NitrocelluloseThe fact that nitrocellulose is soluble in organic solvents such as ether and acetone, made it possible for Georges Audemars to develop the first "artificial silk" about 1855, but his method was impractical for commercial use. Commercial production started in 1891, but the result was flammable, and more expensive than acetate or cuprammonium rayon. Because of this, production was stopped before World War I, for example in 1912 in Germany. Briefly, it became known as "mother-in-law silk."
Nathan Rosenstein invented the spunize process by which he turned rayon from a hard fiber to a fabric. This allowed rayon to become a popular raw material in textiles.
Acetate method
Paul Schützenberger discovered that cellulose can be reacted with acetic anhydride to form cellulose acetate. The triacetate is only[citation needed] soluble in chloroform making the method expensive. The discovery that hydrolyzed cellulose acetate is soluble in more polar solvents, like acetone, made production of cellulose acetate fibers cheap and efficient.
Cuprammonium method
The German chemist Eduard Schweizer discovered that tetraaminecopper dihydroxide could dissolve cellulose. Max Fremery and Johann Urban developed a method to produce carbon fibers for use in light bulbs in 1897. Production of rayon for textiles started in 1899 in the Vereinigte Glanzstofffabriken AG in Oberbruch. Improvement[citation needed] by the J.P. Bemberg AG in 1904 made the artificial silk a product comparable to real silk.
Viscose method
Finally, in 1894, English chemist Charles Frederick Cross, and his collaborators Edward John Bevan, and Clayton Beadle patented their artificial silk, which they named "viscose", because the reaction product of carbon disulfide and cellulose in basic conditions gave a highly viscous solution of xanthate. The first commercial viscose rayon was produced by the UK company Courtaulds Fibers in 1905. Avtex Fibers Incorporated began selling their formulation in the United States in 1910. The name "rayon" was adopted in 1924, with "viscose" being used for the viscous organic liquid used to make both rayon and cellophane. In Europe, though, the fabric itself became known as "viscose," which has been ruled an acceptable alternative term for rayon by the U.S. Federal Trade Commission. The method is able to use wood (cellulose and lignin) as a source of cellulose while the other methods need lignin-free cellulose as starting material. This makes it cheaper and therefore it was used on a larger scale than the other methods.
Contamination of the waste water by carbon disulfide, lignin and the xanthates made this process detrimental to the environment. Rayon was only produced as a filament fiber until the 1930s when it was discovered that broken waste rayon could be used in staple fiber.
The physical properties of rayon were unchanged until the development of high-tenacity rayon in the 1940s. Further research and development led to the creation of high-wet-modulus rayon (HWM rayon) in the 1950s.. Research in the UK was centred on the government-funded British Rayon Research Association.
Major fiber properties
Rayon is a very versatile fiber and has the same comfort properties as natural fibers. It can imitate the feel and texture of silk, wool, cotton and linen. The fibers are easily dyed in a wide range of colors. Rayon fabrics are soft, smooth, cool, comfortable, and highly absorbent, but they do not insulate body heat, making them ideal for use in hot and humid climates. The highest quality Hawaiian shirts produced between the 1930s and the 1950s that are most sought after by collectors are all made of rayon.
The durability and appearance retention of regular rayon are low, especially when wet; also, rayon has the lowest elastic recovery of any fiber. However, HWM rayon is much stronger and exhibits higher durability and appearance retention. Recommended care for regular rayon is dry-cleaning only. HWM rayon can be machine washed.
Physical structure
Regular rayon has lengthwise lines called striations and its cross-section is an indented circular shape. The cross-sections of HWM and cupra rayon are rounder. Filament rayon yarns vary from 80 to 980 filaments per yarn and vary in size from 40 to 5000 denier. Staple fibers range from 1.5 to 15 denier and are mechanically or chemically crimped. Rayon fibers are naturally very bright, but the addition of delustering pigments cuts down on this natural brightness.
Production method
Regular rayon (or viscose) is the most widely produced form of rayon. This method of rayon production has been utilized since the early 1900s and it has the ability to produce either filament or staple fibers. The process is as follows:
1.Cellulose: Production begins with processed cellulose
2.Immersion: The cellulose is dissolved in caustic soda: (C6H10O5)n + nNaOH ? (C6H9O4ONa)n + nH2O
3.Pressing: The solution is then pressed between rollers to remove excess liquid
4.White Crumb: The pressed sheets are crumbled or shredded to produce what is known as "white crumb"
5.Aging: The "white crumb" aged through exposure to oxygen
6.Xanthation: The aged "white crumb" is mixed with carbon disulfide in a process known as Xanthation, the aged alkali cellulose crumbs are placed in vats and are allowed to react with carbon disulfide under controlled temperature (20 to 30°C) to form cellulose xanthate: (C6H9O4ONa)n + nCS2 ? (C6H9O4O-SC-SNa)n
7.Yellow Crumb: Xanthation changes the chemical makeup of the cellulose mixture and the resulting product is now called "yellow crumb"
8.Viscose: The "yellow crumb" is dissolved in a caustic solution to form viscose
9.Ripening: The viscose is set to stand for a period of time, allowing it to ripen: (C6H9O4O-SC-SNa)n + nH2O ? (C6H10O5)n + nCS2 + nNaOH
10.Filtering: After ripening, the viscose is filtered to remove any undissolved particles
11.Degassing: Any bubbles of air are pressed from the viscose in a degassing process
12.Extruding: The viscose solution is extruded through a spinneret, which resembles a shower head with many small holes
13.Acid Bath: As the viscose exits the spinneret, it lands in a bath of sulfuric acid, resulting in the formation of rayon filaments: (C6H9O4O-SC-SNa)n + ½nH2SO4 ? (C6H10O5)n + nCS2 + ½nNa2SO4
14.Drawing: The rayon filaments are stretched, known as drawing, to straighten out the fibers
15.Washing: The fibers are then washed to remove any residual chemicals
16.Cutting: If filament fibers are desired the process ends here. The filaments are cut down when producing staple fibers
High wet modulus rayon (HWM) is a modified version of viscose that has a greater strength when wet. It also has the ability to be mercerized like cotton. HWM rayons are also known as "polynosic" or can be identified by the trade name Modal.
High-tenacity rayon is another modified version of viscose that has almost twice the strength of HWM. This type of rayon is typically used for industrial purposes such as tire cord.
Cupramonium rayon has properties similar to viscose but during production, the cellulose is combined with copper and ammonia (Schweizer's reagent). Due to the environmental effects of this production method, cupramonium rayon is no longer produced in the United States.
Disposal and biodegradability
The biodegradability of fibers in soil burial and sewage sludge was evaluated by Korean researchers who found that biodegradability decreased in the following order: rayon, cotton, acetate (meaning rayon decays more readily than cotton). The ability of individual rayon-based fabrics to repel water was negatively correlated with their speed of degradation (meaning the greater the water-repelling ability of the fibre, the slower it will decompose).
Producers
Trade names are used within the rayon industry to determine the type of rayon used.
Look up Bemberg in Wiktionary, the free dictionary.
Bemberg, for example, is a trade name for cupramonium rayon developed by J.P. Bemberg that is now only produced in Italy due to United States Environmental Protection Agency regulations in the US.
Modal and Tencel are widely used forms of rayon produced by Lenzing Fibers Corp. which is based in northern Austria.
Galaxy, Danufil, and Viloft are rayon brands produced by Kelheim Fibres, a German manufacturer.
Acordis is a major manufacturer of cellulose based fibers and yarns. Production facilities can be found throughout Europe, the U.S. and Brazil.
Visil rayon is a flame retardant form of viscose which has silica embedded in the fiber during manufacturing.
North American Rayon Corp of Tennessee produced viscose rayon until its closure in the year 2000.
Grasim of India is the largest producer of rayon in the world (claiming 24% market share). It has plants in Nagda, Kharach and Harihar - all in India.
See also For a description of the production method at a factory in Germany in World War II, see pages 152-155 of
Agnès Humbert, (tr. Barbara Mellor) Résistance: Memoirs of Occupied France, London, Bloomsbury Publishing PLC, 2008 ISBN 9780747595977 (American title: Resistance: A Frenchwoman's Journal of the War, Bloomsbury, USA, 2008)
Nylon
Nylon is a generic designation for a family of synthetic polymers known generically as polyamides, first produced on February 28, 1935, by Wallace Carothers at DuPont's research facility at the DuPont Experimental Station. Nylon is one of the most commonly used polymers
Nylon is a thermoplastic silky material, first used commercially in a nylon-bristled toothbrush (1938), followed more famously by women's stockings ("nylons"; 1940). It is made of repeating units linked by amide bonds and is frequently referred to as polyamide (PA). Nylon was the first commercially successful synthetic polymer. There are two common methods of making nylon for fiber applications. In one approach, molecules with an acid (COOH) group on each end are reacted with molecules containing amine (NH2) groups on each end. The resulting nylon is named on the basis of the number of carbon atoms separating the two acid groups and the two amines. These are formed into monomers of intermediate molecular weight, which are then reacted to form long polymer chains.
Nylon was intended to be a synthetic replacement for silk and substituted for it in many different products after silk became scarce during World War II. It replaced silk in military applications such as parachutes and flak vests, and was used in many types of vehicle tires.
Nylon fibres are used in many applications, including fabrics, bridal veils, carpets, musical strings, and rope.
Solid nylon is used for mechanical parts such as machine screws, gears and other low- to medium-stress components previously cast in metal. Engineering-grade nylon is processed by extrusion, casting, and injection molding. Solid nylon is used in hair combs. Type 6,6 Nylon 101 is the most common commercial grade of nylon, and Nylon 6 is the most common commercial grade of molded nylon. Nylon is available in glass-filled variants which increase structural and impact strength and rigidity, and molybdenum sulfide-filled variants which increase lubricity.
Aramids are another type of polyamide with quite different chain structures which include aromatic groups in the main chain. Such polymers make excellent ballistic fibres.
Chemistry
Nylons are condensation copolymers formed by reacting equal parts of a diamine and a dicarboxylic acid, so that amides are formed at both ends of each monomer in a process analogous to polypeptide biopolymers. Chemical elements included are carbon, hydrogen, nitrogen, and oxygen. The numerical suffix specifies the numbers of carbons donated by the monomers; the diamine first and the diacid second. The most common variant is nylon 6-6 which refers to the fact that the diamine (hexamethylene diamine, IUPAC name: 1,6-diaminohexane) and the diacid (adipic acid, IUPAC name: hexane-1,6-dicarboxylic acid) each donate 6 carbons to the polymer chain. As with other regular copolymers like polyesters and polyurethanes, the "repeating unit" consists of one of each monomer, so that they alternate in the chain. Since each monomer in this copolymer has the same reactive group on both ends, the direction of the amide bond reverses between each monomer, unlike natural polyamide proteins which have overall directionality: C terminal ? N terminal. In the laboratory, nylon 6-6 can also be made using adipoyl chloride instead of adipic.
It is difficult to get the proportions exactly correct, and deviations can lead to chain termination at molecular weights less than a desirable 10,000 daltons (u). To overcome this problem, a crystalline, solid "nylon salt" can be formed at room temperature, using an exact 1:1 ratio of the acid and the base to neutralize each other. Heated to 285 °C (545 °F), the salt reacts to form nylon polymer. Above 20,000 daltons, it is impossible to spin the chains into yarn, so to combat this, some acetic acid is added to react with a free amine end group during polymer elongation to limit the molecular weight. In practice, and especially for 6,6, the monomers are often combined in a water solution. The water used to make the solution is evaporated under controlled conditions, and the increasing concentration of "salt" is polymerized to the final molecular weight.
DuPont patented[1] nylon 6,6, so in order to compete, other companies (particularly the German BASF) developed the homopolymer nylon 6, or polycaprolactam — not a condensation polymer, but formed by a ring-opening polymerization (alternatively made by polymerizing aminocaproic acid). The peptide bond within the caprolactam is broken with the exposed active groups on each side being incorporated into two new bonds as the monomer becomes part of the polymer backbone. In this case, all amide bonds lie in the same direction, but the properties of nylon 6 are sometimes indistinguishable from those of nylon 6,6 — except for melt temperature and some fiber properties in products like carpets and textiles. There is also nylon 9.
The 428 °F (220 °C) melting point of nylon 6 is lower than the 509 °F (265 °C) melting point of nylon 6,6.
Nylon 5,10, made from pentamethylene diamine and sebacic acid, was studied by Carothers even before nylon 6,6 and has superior properties, but is more expensive to make. In keeping with this naming convention, "nylon 6,12" (N-6,12) or "PA-6,12" is a copolymer of a 6C diamine and a 12C diacid. Similarly for N-5,10 N-6,11; N-10,12, etc. Other nylons include copolymerized dicarboxylic acid/diamine products that are not based upon the monomers listed above. For example, some aromatic nylons are polymerized with the addition of diacids like terephthalic acid (? Kevlar Twaron) or isophthalic acid (? Nomex), more commonly associated with polyesters. There are copolymers of N-6,6/N6; copolymers of N-6,6/N-6/N-12; and others. Because of the way polyamides are formed, nylon would seem to be limited to unbranched, straight chains. But "star" branched nylon can be produced by the condensation of dicarboxylic acids with polyamines having three or more amino groups.
Concepts of nylon production
The first approach: combining molecules with an acid (COOH) group on each end are reacted with two chemicals that contain amine (NH2) groups on each end. This process creates nylon 6,6, made of hexamethylene diamine with six carbon atoms and adipic acid.
The second approach: a compound has an acid at one end and an amine at the other and is polymerized to form a chain with repeating units of (-NH-[CH2]n-CO-)x. In other words, nylon 6 is made from a single six-carbon substance called caprolactam. In this equation, if n=5, then nylon 6 is the assigned name (may also be referred to as polymer).
The characteristic features of nylon 6,6 include:
Pleats and creases can be heat-set at higher temperatures
More compact molecular structure
Better weathering properties; better sunlight resistance
Softer "Hand"
Higher melting point (256 °C / 492.8 °F)
Superior colorfastness
Excellent abrasion resistance
On the other hand, nylon 6 is easy to dye, more readily fades; it has a higher impact resistance, a more rapid moisture absorption, greater elasticity and elastic recovery.
Characteristics
Variation of luster: nylon has the ability to be very lustrous, semilustrous or dull.
Durability: its high tenacity fibers are used for seatbelts, tire cords, ballistic cloth and other uses.
High elongation
Excellent abrasion resistance
Highly resilient (nylon fabrics are heat-set)
Paved the way for easy-care garments
High resistance to insects, fungi, animals, as well as molds, mildew, rot and many chemicals
Used in carpets and nylon stockings
Melts instead of burning
Used in many military applications
Good specific strength
Transparent under infrared light (-12dB)
Bulk properties
Above their melting temperatures, Tm, thermoplastics like nylon are amorphous solids or viscous fluids in which the chains approximate random coils. Below Tm, amorphous regions alternate with regions which are lamellar crystals. The amorphous regions contribute elasticity and the crystalline regions contribute strength and rigidity. The planar amide (-CO-NH-) groups are very polar, so nylon forms multiple hydrogen bonds among adjacent strands. Because the nylon backbone is so regular and symmetrical, especially if all the amide bonds are in the trans configuration, nylons often have high crystallinity and make excellent fibers. The amount of crystallinity depends on the details of formation, as well as on the kind of nylon. Apparently it can never be quenched from a melt as a completely amorphous solid.
Nylon 6,6 can have multiple parallel strands aligned with their neighboring peptide bonds at coordinated separations of exactly 6 and 4 carbons for considerable lengths, so the carbonyl oxygens and amide hydrogens can line up to form interchain hydrogen bonds repeatedly, without interruption. Nylon 5,10 can have coordinated runs of 5 and 8 carbons. Thus parallel (but not antiparallel) strands can participate in extended, unbroken, multi-chain ?-pleated sheets, a strong and tough supermolecular structure similar to that found in natural silk fibroin and the ?-keratins in feathers. (Proteins have only an amino acid ?-carbon separating sequential -CO-NH- groups.) Nylon 6 will form uninterrupted H-bonded sheets with mixed directionalities, but the ?-sheet wrinkling is somewhat different. The three-dimensional disposition of each alkane hydrocarbon chain depends on rotations about the 109.47° tetrahedral bonds of singly-bonded carbon atoms.
When extruded into fibers through pores in an industrial spinneret, the individual polymer chains tend to align because of viscous flow. If subjected to cold drawing afterwards, the fibers align further, increasing their crystallinity, and the material acquires additional tensile strength. In practice, nylon fibers are most often drawn using heated rolls at high speeds.
Block nylon tends to be less crystalline, except near the surfaces due to shearing stresses during formation. Nylon is clear and colorless, or milky, but is easily dyed. Multistranded nylon cord and rope is slippery and tends to unravel. The ends can be melted and fused with a heat source such as a flame or electrode to prevent this.
When dry, polyamide is a good electrical insulator. However, polyamide is hygroscopic. The absorption of water will change some of the material's properties such as its electrical resistance. Nylon is less absorbent than wool or cotton.
Historical uses
Bill Pittendreigh, DuPont, and other individuals and corporations worked diligently during the first few months of World War II to find a way to replace Asian silk and hemp with nylon in parachutes. It was also used to make tires, tents, ropes, ponchos, and other military supplies. It was even used in the production of a high-grade paper for U.S. currency. At the outset of the war, cotton accounted for more than 80% of all fibers used and manufactured, and wool fibers accounted for the remaining 20%. By August 1945, manufactured fibers had taken a market share of 25% and cotton had dropped.
Some of the terpolymers based upon nylon are used every day in packaging. Nylon has been used for meat wrappings and sausage sheaths.
Use in composites
Nylon can be used as the matrix material in composite materials, with reinforcing fibres like glass or carbon fiber; such a composite has a higher density than pure nylon. Such thermoplastic composites (25% glass fibre) are frequently used in car components next to the engine, such as intake manifolds, where the good heat resistance of such materials makes them feasible competitors to metals.
Hydrolysis and degradation
All nylons are susceptible to hydrolysis, especially by strong acids, a reaction essentially the reverse of the synthetic reaction shown above. The molecular weight of nylon products so attacked drops fast, and cracks form quickly at the affected zones. Lower members of the nylons (such as nylon 6) are affected more than higher members such as nylon 12. This means that nylon parts cannot be used in contact with sulfuric acid for example, such as the electrolyte used in lead-acid batteries. When being molded, nylon must be dried to prevent hydrolysis in the molding machine barrel since water at high temperatures can also degrade the polymer. The reaction is of the type:
Incineration and recycling
Various nylons break down in fire and form hazardous smoke, and toxic fumes or ash, typically containing hydrogen cyanide. Incinerating nylons to recover the high energy used to create them is usually expensive, so most nylons reach the garbage dumps, decaying very slowly. Some recycling is done on nylon, usually creating pellets for reuse in the industry, but this is done at a much lower scale
Etymology
In 1940, John W. Eckelberry of DuPont stated that the letters "nyl" were arbitrary and the "on" was copied from the suffixes of other fibers such as cotton and rayon. A later publication by DuPont explained that the name was originally intended to be "No-Run" ("run" meaning "unravel"), but was modified to avoid making such an unjustified claim and to make the word sound better. An apocryphal tale is that Nylon is a conflation of "New York" and "London". Equally spurious is the backronym for "Now You've Lost, Old Nippon" referring to the supposed loss of demand for Japanese silk.
Polyester
Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate (PET). Polyesters include naturally-occurring chemicals, such as in the cutin of plant cuticles, as well as synthetics through step-growth polymerization such as polycarbonate and polybutyrate. Natural polyesters and a few synthetic ones are biodegradable, but most synthetic polyesters are not.
Depending on the chemical structure polyester can be a thermoplastic or thermoset, however the most common polyesters are thermoplastics.
Fabrics woven from polyester thread or yarn are used extensively in apparel and home furnishings, from shirts and pants to jackets and hats, bed sheets, blankets and upholstered furniture. Industrial polyester fibers, yarns and ropes are used in tyre reinforcements, fabrics for conveyor belts, safety belts, coated fabrics and plastic reinforcements with high-energy absorption. Polyester fiber is used as cushioning and insulating material in pillows, comforters and upholstery padding.
While synthetic clothing in general is perceived by many as having a less-natural feel compared to fabrics woven from natural fibres (such as cotton and wool), polyester fabrics can provide specific advantages over natural fabrics, such as improved wrinkle resistance, durability and high color retention. As a result, polyester fibres are sometimes spun together with natural fibres to produce a cloth with blended properties. Synthetic fibres also can create materials with superior water, wind and environmental resistance compared to plant-derived fibres.
Polyesters are also used to make "plastic" bottles, films, tarpaulin, canoes, liquid crystal displays, holograms, filters, dielectric film for capacitors, film insulation for wire and insulating tapes.
Liquid crystalline polyesters are among the first industrially-used liquid crystal polymers. They are used for their mechanical properties and heat-resistance. These traits are also important in their application as an abradable seal in jet engines.
Polyesters are widely used as a finish on high-quality wood products such as guitars, pianos and vehicle/yacht interiors. Burns Guitars, Rolls Royce and Sunseeker are a few companies that use polyesters to finish their products. Thixotropic properties of spray-applicable polyesters make them ideal for use on open-grain timbers, as they can quickly fill wood grain, with a high-build film thickness per coat. Cured polyesters can be sanded and polished to a high-gloss, durable finish.
Types
Polyesters as thermoplastics may change shape after the application of heat. While combustible at high temperatures, polyesters tend to shrink away from flames and self-extinguish upon ignition. Polyester fibres have high tenacity and E-modulus as well as low water absorption and minimal shrinkage in comparison with other industrial fibres.
Unsaturated polyesters (UPR) are thermosetting resins. They are used as casting materials, fiberglass laminating resins and non-metallic auto-body fillers. Fibreglass-reinforced unsaturated polyesters find wide application in bodies of yachts and as body parts of cars.
Increasing the aromatic parts of polyesters increases their glass transition temperature, melting temperature, thermal stability, chemical stability...
Polyesters can also be telechelic oligomers like the polycaprolactone diol (PCL) and the polyethylene adipate diol (PEA). They are then used as prepolymers.
Industry
Basics
Polyester is a synthetic polymer made of purified terephthalic acid (PTA) or its dimethyl ester dimethyl terephthalate (DMT) and monoethylene glycol (MEG). With 18% market share of all plastic materials produced, it ranges third after polyethylene (33.5%) and polypropylene (19.5%).
The main raw materials are described as follows:
Purified terephthalic acid – PTA – CAS-No.: 100-21-0
Synonym: 1,4 benzenedicarboxylic acid,
Sum formula; C6H4(COOH)2 , mol weight: 166.13
Dimethylterephthalate – DMT – CAS-No: 120-61-6
Synonym: 1,4 benzenedicarboxylic acid dimethyl ester
Sum formula C6H4(COOCH3)2 , mol weight: 194.19
Mono Ethylene Glycol – MEG – CAS No.: 107-21-1
Synonym: 1,2 ethanediol
Sum formula: C2H6O2 , mol weight: 62,07
To make a polymer of high molecular weight a catalyst is needed. The most common catalyst is antimony trioxide (or antimony tri acetate):
Antimony trioxide – ATO – CAS-No.: 1309-64-4 Molecular weight: 291.51 Sum formula: Sb2O3
In 2008, about 10,000 tonnes Sb2O3 were used to produce around 49 million tonnes polyethylene terephthalate.
Polyester is described as follows:
Polyethylene Terephthalate CAS-No.: 25038-59-9 Synonym/abbreviations: polyester, PET, PES Sum Formula: H-[C10H8O4]-n=60–120 OH, molelcular unit weight: 192.17
There are several reasons for the importance of Polyester:
The relatively easy accessible raw materials PTA or DMT and MEG
The very well understood and described simple chemical process of polyester synthesis
The low toxicity level of all raw materials and side products during polyester production and processing
The possibility to produce PET in a closed loop at low emissions to the environment
The outstanding mechanical and chemical properties of polyester
The recyclability
The wide variety of intermediate and final products made of polyester.
In table 1 the estimated world polyester production is shown. Main applications are textile polyester, bottle polyester resin, film polyester mainly for packaging and specialty polyesters for engineering plastics. According to this table, the world's total polyester production might exceed 50 million tons per annum before the year 2010.
Table 1: World polyester production
Market size per year Product type 2002 [Million tonnes/year] 2008 [Million tonnes/year]
Textile-PET 20 39
Resin, bottle/A-PET 9 16
Film-PET 1.2 1.5
Special polyester 1 2.5
Total 31.2 49
Raw material producerThe raw materials PTA, DMT, and MEG are mainly produced by large chemical companies which are sometimes integrated down to the crude oil refinery where p-Xylene is the base material to produce PTA and liquefied petroleum gas (LPG) is the base material to produce MEG. Large PTA producers are for instance BP, Reliance, Sinopec, SK-Chemicals, Mitsui, and Eastman Chemicals. MEG production is in the hand of about 10 global players which are headed by MEGlobal a JV of DOW and PIC Kuweit followed by Sabic.
Polyester processingAfter the first stage of polymer production in the melt phase, the product stream divides into two different application areas which are mainly textile applications and packaging applications. In figure 2 the main applications of textile and packaging polyester are listed.
Table 2: Textile and packaging polyester application list
Polyester-based polymer (melt or pellet) Textile Packaging
Staple fiber (PSF) Bottles for CSD, Water, Beer, Juice, Detergents
Filaments POY, DTY, FDY A-PET Film
Technical yarn and tire cord Thermoforming
Non-woven and spunbond BO-PET Biaxial oriented Film
Mono-filament Strapping
Abbreviations: PSF = Polyester Staple Fiber; POY = Partially Oriented Yarn; DTY = Draw Textured Yarn; FDY = Fully Drawn Yarn; CSD = Carbonated Soft Drink; A-PET = Amorphous Polyester Film; BO-PET = Biaxial Oriented Polyester Film;
A comparable small market segment (much less than 1 million tonnes/year) of polyester is used to produce engineering plastics and masterbatch.
In order to produce the polyester melt with a high efficiency, high-output processing steps like staple fiber (50–300 tonnes/day per spinning line) or POY /FDY (up to 600 tonnes/day split into about 10 spinning machines) are meanwhile more and more horizontal, integrated, direct processes. This means the polymer melt is directly converted into the textile fibers or filaments without the common step of pelletizing. We are talking about full horizontal integration when polyester is produced at one site starting from crude oil or distillation products in the chain oil ? benzene ? PX ? PTA ? PET melt ? fiber/filament or bottle-grade resin. Such integrated processes are meanwhile established in more or less interrupted processes at one production site. Eastman Chemicals introduced at first the idea to close the chain from PX to PET resin with their so-called INTEGREX process. The capacity of such horizontal, integrated productions sites is >1000 tonnes/day and can easily reach 2500 tonnes/day.
Besides the above mentioned large processing units to produce staple fiber or yarns, there are ten thousands of small and very small processing plants, so that one can estimate that polyester is processed and recycled in more than 10 000 plants around the globe. This is without counting all the companies involved in the supply industry, beginning with engineering and processing machines and ending with special additives, stabilizers and colors. This is a gigantic industry complex and it is still growing by 4–8% per annum, depending on the world region. Useful information about the polyester industry can be found under where a “Who is Producing What in the Polyester Industry” is gradually being developed.
Polyester (1953)
Carbon fiber (1968)
Specialty synthetic fibers include:
Vinyon (1939)
Saran (1941)
Spandex (1959)
Vinalon (1939)
Aramids (1961) - known as Nomex, Kevlar and Twaron
Modal (1960's)
Dyneema/Spectra (1979)
PBI (Polybenzimidazole fiber) (1983)
Sulfar (1983)
Lyocell (1992)
PLA (2002)
M-5 (PIPD fiber)
Orlon
Zylon (PBO fiber)
Vectran (TLCP fiber) made from Vectra LCP polymer
Derclon used in manufacture of rugs
Other synthetic materials used in fibers include:
Acrylonitrile rubber (1930)
Modern fibers that are made from older artificial materials include:
Glass Fiber (1938) is used for:
industrial, automotive, and home insulation (Glass wool)
reinforcement of composite materials (Glass-reinforced plastic, Glass fiber reinforced concrete)
specialty papers in battery separators and filtration
Metallic fiber (1946) is used for:
adding metallic properties to clothing for the purpose of fashion (usually made with composite plastic and metal foils)
elimination and prevention of static charge build-up
conducting electricity to transmit information
conduction of heat
In the horticulture industry synthetics are often used in soils to help the plants grow better. Examples are:
expanded polystyrene flakes
urea-formaldehyde foam resin
polyurethane foam
phenolic resin foam
Industry structureDuring the last quarter of 20th century, Asian share of global output of synthetic fibers doubled to 65 per cent.
Synthesis
Synthesis of polyesters is generally achieved by a polycondensation reaction. See "condensation reactions in polymer chemistry". The general equation for the reaction of a diol with a diacid is :
(n+1) R(OH)2 + n R´(COOH)2 ? HO[ROOCR´COO]nROH + 2n H2O
[edit] Azeotrope esterificationIn this classical method, an alcohol and a carboxylic acid react to form a carboxylic ester. To assemble a polymer, the water formed by the reaction must be continually removed by azeotrope distillation.
Acylation (HCl method)The acid begins as an acid chloride, and thus the polycondensation proceeds with emission of hydrochloric acid (HCl) instead of water. This method can be carried out in solution or as an enamel.
Silyl method
In this variant of the HCl method, the carboxylic acid chloride is converted with the trimethyl silyl ether of the alcohol component and production of trimethyl silyl chloride is obtained
Acetate method (esterification)
Silyl acetate method
Ring-opening polymerization
Aliphatic polyesters can be assembled from lactones under very mild conditions, catalyzed anionically, cationically or metallorganically.
Cross-linking
Unsaturated polyesters are thermosetting resins. They are generally copolymers prepared by polymerizing one or more diol with saturated and unsaturated dicarboxylic acids (maleic acid, fumaric acid...) or their anhydrides. The double bond of unsaturated polyesters reacts with a vinyl monomer mainly the styrene, resulting in a 3-D cross-linked structure. This structure acts as a thermoset. The cross-linking is initiated through an exothermic reaction involving an organic peroxide, such as methyl ethyl ketone peroxide or benzoyl peroxide.
Health effects
A study published in 1993 found that polyester underwear reduced sperm count and sperm motility in male dogs. Similar studies have shown similar results in humans and rats. The cause is not known but is believed to be due to an electrostatic field created by the fabric.
Synthetic and artificial fiber
Image by Joost J. Bakker IJmuiden
Synthetic and artificial fiber
Synthetic fibers are the result of extensive research by scientists to improve on naturally occurring animal and plant fibers. In general, synthetic fibers are created by forcing, usually through extrusion, fiber forming materials through holes (called spinnerets) into the air, forming a thread. Before synthetic fibers were developed, artificially manufactured fibers were made from cellulose, which comes from plants. These fibers are called cellulose fibers.
Synthetic fibers account for about half of all fiber usage, with applications in every field of fiber and textile technology. Although many classes of fiber based on synthetic polymers have been evaluated as potentially valuable commercial products, four of them - nylon, polyester, acrylic and polyolefin - dominate the market. These four account for approximately 98 per cent by volume of synthetic fiber production, with polyester alone accounting for around 60 per cent.
HistoryThe first artificial fiber, known as artificial silk, became known as viscose around 1894, and finally rayon in 1924. A similar product known as cellulose acetate was discovered in 1865. Rayon and acetate are both artificial fibers, but not truly synthetic, being made from wood. Although these artificial fibers were discovered in the mid-nineteenth century, successful modern manufacture began much later (see the dates below).
Nylon, the first synthetic fiber, made its debut in the United States as a replacement for silk, just in time for World War II rationing. Its novel use as a material for women's stockings overshadowed more practical uses, such as a replacement for the silk in parachutes and other military uses.
Common synthetic fibers include:
Rayon (1910) (artificial, not synthetic)
Acetate (1924) (artificial, not synthetic)
Nylon (1939)
Modacrylic (1949)
Olefin (1949)
Acrylic (1950)
Rayon
Rayon is a manufactured regenerated cellulose fiber. Because it is produced from naturally occurring polymers, it is neither a truly synthetic fiber nor a natural fiber; it is a semi-synthetic or artificial fiber. Rayon is known by the names viscose rayon and art silk in the textile industry. It usually has a high luster quality giving it a bright sheen.
Uses
Some major rayon fiber uses include apparel (e.g. blouses, dresses, jackets, lingerie, linings, scarves, suits, neckties, hats, socks), the filling in Zippo lighters, furnishings (e.g. bedspreads, bedsheets, blankets, window treatments, upholstery, slipcovers), industrial uses (e.g. medical surgery products, non-woven products, tire cord), and other uses (e.g. yarn, feminine hygiene products, diapers, towels). Rayon is a major feedstock in the production of carbon fiber.
In early 2010, the U.S. Federal Trade Commission warned several retailers that six major manufacturers were falsely labeling rayon products as "bamboo", in order to appeal to environmentally conscious consumers. While rayon may be produced with bamboo as a raw material, and the two may be used for similar fabrics (though natural bamboo is not as smooth), rayon is so far removed from bamboo by chemical processing that the two are entirely separate.
History
NitrocelluloseThe fact that nitrocellulose is soluble in organic solvents such as ether and acetone, made it possible for Georges Audemars to develop the first "artificial silk" about 1855, but his method was impractical for commercial use. Commercial production started in 1891, but the result was flammable, and more expensive than acetate or cuprammonium rayon. Because of this, production was stopped before World War I, for example in 1912 in Germany. Briefly, it became known as "mother-in-law silk."
Nathan Rosenstein invented the spunize process by which he turned rayon from a hard fiber to a fabric. This allowed rayon to become a popular raw material in textiles.
Acetate method
Paul Schützenberger discovered that cellulose can be reacted with acetic anhydride to form cellulose acetate. The triacetate is only[citation needed] soluble in chloroform making the method expensive. The discovery that hydrolyzed cellulose acetate is soluble in more polar solvents, like acetone, made production of cellulose acetate fibers cheap and efficient.
Cuprammonium method
The German chemist Eduard Schweizer discovered that tetraaminecopper dihydroxide could dissolve cellulose. Max Fremery and Johann Urban developed a method to produce carbon fibers for use in light bulbs in 1897. Production of rayon for textiles started in 1899 in the Vereinigte Glanzstofffabriken AG in Oberbruch. Improvement[citation needed] by the J.P. Bemberg AG in 1904 made the artificial silk a product comparable to real silk.
Viscose method
Finally, in 1894, English chemist Charles Frederick Cross, and his collaborators Edward John Bevan, and Clayton Beadle patented their artificial silk, which they named "viscose", because the reaction product of carbon disulfide and cellulose in basic conditions gave a highly viscous solution of xanthate. The first commercial viscose rayon was produced by the UK company Courtaulds Fibers in 1905. Avtex Fibers Incorporated began selling their formulation in the United States in 1910. The name "rayon" was adopted in 1924, with "viscose" being used for the viscous organic liquid used to make both rayon and cellophane. In Europe, though, the fabric itself became known as "viscose," which has been ruled an acceptable alternative term for rayon by the U.S. Federal Trade Commission. The method is able to use wood (cellulose and lignin) as a source of cellulose while the other methods need lignin-free cellulose as starting material. This makes it cheaper and therefore it was used on a larger scale than the other methods.
Contamination of the waste water by carbon disulfide, lignin and the xanthates made this process detrimental to the environment. Rayon was only produced as a filament fiber until the 1930s when it was discovered that broken waste rayon could be used in staple fiber.
The physical properties of rayon were unchanged until the development of high-tenacity rayon in the 1940s. Further research and development led to the creation of high-wet-modulus rayon (HWM rayon) in the 1950s.. Research in the UK was centred on the government-funded British Rayon Research Association.
Major fiber properties
Rayon is a very versatile fiber and has the same comfort properties as natural fibers. It can imitate the feel and texture of silk, wool, cotton and linen. The fibers are easily dyed in a wide range of colors. Rayon fabrics are soft, smooth, cool, comfortable, and highly absorbent, but they do not insulate body heat, making them ideal for use in hot and humid climates. The highest quality Hawaiian shirts produced between the 1930s and the 1950s that are most sought after by collectors are all made of rayon.
The durability and appearance retention of regular rayon are low, especially when wet; also, rayon has the lowest elastic recovery of any fiber. However, HWM rayon is much stronger and exhibits higher durability and appearance retention. Recommended care for regular rayon is dry-cleaning only. HWM rayon can be machine washed.
Physical structure
Regular rayon has lengthwise lines called striations and its cross-section is an indented circular shape. The cross-sections of HWM and cupra rayon are rounder. Filament rayon yarns vary from 80 to 980 filaments per yarn and vary in size from 40 to 5000 denier. Staple fibers range from 1.5 to 15 denier and are mechanically or chemically crimped. Rayon fibers are naturally very bright, but the addition of delustering pigments cuts down on this natural brightness.
Production method
Regular rayon (or viscose) is the most widely produced form of rayon. This method of rayon production has been utilized since the early 1900s and it has the ability to produce either filament or staple fibers. The process is as follows:
1.Cellulose: Production begins with processed cellulose
2.Immersion: The cellulose is dissolved in caustic soda: (C6H10O5)n + nNaOH ? (C6H9O4ONa)n + nH2O
3.Pressing: The solution is then pressed between rollers to remove excess liquid
4.White Crumb: The pressed sheets are crumbled or shredded to produce what is known as "white crumb"
5.Aging: The "white crumb" aged through exposure to oxygen
6.Xanthation: The aged "white crumb" is mixed with carbon disulfide in a process known as Xanthation, the aged alkali cellulose crumbs are placed in vats and are allowed to react with carbon disulfide under controlled temperature (20 to 30°C) to form cellulose xanthate: (C6H9O4ONa)n + nCS2 ? (C6H9O4O-SC-SNa)n
7.Yellow Crumb: Xanthation changes the chemical makeup of the cellulose mixture and the resulting product is now called "yellow crumb"
8.Viscose: The "yellow crumb" is dissolved in a caustic solution to form viscose
9.Ripening: The viscose is set to stand for a period of time, allowing it to ripen: (C6H9O4O-SC-SNa)n + nH2O ? (C6H10O5)n + nCS2 + nNaOH
10.Filtering: After ripening, the viscose is filtered to remove any undissolved particles
11.Degassing: Any bubbles of air are pressed from the viscose in a degassing process
12.Extruding: The viscose solution is extruded through a spinneret, which resembles a shower head with many small holes
13.Acid Bath: As the viscose exits the spinneret, it lands in a bath of sulfuric acid, resulting in the formation of rayon filaments: (C6H9O4O-SC-SNa)n + ½nH2SO4 ? (C6H10O5)n + nCS2 + ½nNa2SO4
14.Drawing: The rayon filaments are stretched, known as drawing, to straighten out the fibers
15.Washing: The fibers are then washed to remove any residual chemicals
16.Cutting: If filament fibers are desired the process ends here. The filaments are cut down when producing staple fibers
High wet modulus rayon (HWM) is a modified version of viscose that has a greater strength when wet. It also has the ability to be mercerized like cotton. HWM rayons are also known as "polynosic" or can be identified by the trade name Modal.
High-tenacity rayon is another modified version of viscose that has almost twice the strength of HWM. This type of rayon is typically used for industrial purposes such as tire cord.
Cupramonium rayon has properties similar to viscose but during production, the cellulose is combined with copper and ammonia (Schweizer's reagent). Due to the environmental effects of this production method, cupramonium rayon is no longer produced in the United States.
Disposal and biodegradability
The biodegradability of fibers in soil burial and sewage sludge was evaluated by Korean researchers who found that biodegradability decreased in the following order: rayon, cotton, acetate (meaning rayon decays more readily than cotton). The ability of individual rayon-based fabrics to repel water was negatively correlated with their speed of degradation (meaning the greater the water-repelling ability of the fibre, the slower it will decompose).
Producers
Trade names are used within the rayon industry to determine the type of rayon used.
Look up Bemberg in Wiktionary, the free dictionary.
Bemberg, for example, is a trade name for cupramonium rayon developed by J.P. Bemberg that is now only produced in Italy due to United States Environmental Protection Agency regulations in the US.
Modal and Tencel are widely used forms of rayon produced by Lenzing Fibers Corp. which is based in northern Austria.
Galaxy, Danufil, and Viloft are rayon brands produced by Kelheim Fibres, a German manufacturer.
Acordis is a major manufacturer of cellulose based fibers and yarns. Production facilities can be found throughout Europe, the U.S. and Brazil.
Visil rayon is a flame retardant form of viscose which has silica embedded in the fiber during manufacturing.
North American Rayon Corp of Tennessee produced viscose rayon until its closure in the year 2000.
Grasim of India is the largest producer of rayon in the world (claiming 24% market share). It has plants in Nagda, Kharach and Harihar - all in India.
See also For a description of the production method at a factory in Germany in World War II, see pages 152-155 of
Agnès Humbert, (tr. Barbara Mellor) Résistance: Memoirs of Occupied France, London, Bloomsbury Publishing PLC, 2008 ISBN 9780747595977 (American title: Resistance: A Frenchwoman's Journal of the War, Bloomsbury, USA, 2008)
Nylon
Nylon is a generic designation for a family of synthetic polymers known generically as polyamides, first produced on February 28, 1935, by Wallace Carothers at DuPont's research facility at the DuPont Experimental Station. Nylon is one of the most commonly used polymers
Nylon is a thermoplastic silky material, first used commercially in a nylon-bristled toothbrush (1938), followed more famously by women's stockings ("nylons"; 1940). It is made of repeating units linked by amide bonds and is frequently referred to as polyamide (PA). Nylon was the first commercially successful synthetic polymer. There are two common methods of making nylon for fiber applications. In one approach, molecules with an acid (COOH) group on each end are reacted with molecules containing amine (NH2) groups on each end. The resulting nylon is named on the basis of the number of carbon atoms separating the two acid groups and the two amines. These are formed into monomers of intermediate molecular weight, which are then reacted to form long polymer chains.
Nylon was intended to be a synthetic replacement for silk and substituted for it in many different products after silk became scarce during World War II. It replaced silk in military applications such as parachutes and flak vests, and was used in many types of vehicle tires.
Nylon fibres are used in many applications, including fabrics, bridal veils, carpets, musical strings, and rope.
Solid nylon is used for mechanical parts such as machine screws, gears and other low- to medium-stress components previously cast in metal. Engineering-grade nylon is processed by extrusion, casting, and injection molding. Solid nylon is used in hair combs. Type 6,6 Nylon 101 is the most common commercial grade of nylon, and Nylon 6 is the most common commercial grade of molded nylon. Nylon is available in glass-filled variants which increase structural and impact strength and rigidity, and molybdenum sulfide-filled variants which increase lubricity.
Aramids are another type of polyamide with quite different chain structures which include aromatic groups in the main chain. Such polymers make excellent ballistic fibres.
Chemistry
Nylons are condensation copolymers formed by reacting equal parts of a diamine and a dicarboxylic acid, so that amides are formed at both ends of each monomer in a process analogous to polypeptide biopolymers. Chemical elements included are carbon, hydrogen, nitrogen, and oxygen. The numerical suffix specifies the numbers of carbons donated by the monomers; the diamine first and the diacid second. The most common variant is nylon 6-6 which refers to the fact that the diamine (hexamethylene diamine, IUPAC name: 1,6-diaminohexane) and the diacid (adipic acid, IUPAC name: hexane-1,6-dicarboxylic acid) each donate 6 carbons to the polymer chain. As with other regular copolymers like polyesters and polyurethanes, the "repeating unit" consists of one of each monomer, so that they alternate in the chain. Since each monomer in this copolymer has the same reactive group on both ends, the direction of the amide bond reverses between each monomer, unlike natural polyamide proteins which have overall directionality: C terminal ? N terminal. In the laboratory, nylon 6-6 can also be made using adipoyl chloride instead of adipic.
It is difficult to get the proportions exactly correct, and deviations can lead to chain termination at molecular weights less than a desirable 10,000 daltons (u). To overcome this problem, a crystalline, solid "nylon salt" can be formed at room temperature, using an exact 1:1 ratio of the acid and the base to neutralize each other. Heated to 285 °C (545 °F), the salt reacts to form nylon polymer. Above 20,000 daltons, it is impossible to spin the chains into yarn, so to combat this, some acetic acid is added to react with a free amine end group during polymer elongation to limit the molecular weight. In practice, and especially for 6,6, the monomers are often combined in a water solution. The water used to make the solution is evaporated under controlled conditions, and the increasing concentration of "salt" is polymerized to the final molecular weight.
DuPont patented[1] nylon 6,6, so in order to compete, other companies (particularly the German BASF) developed the homopolymer nylon 6, or polycaprolactam — not a condensation polymer, but formed by a ring-opening polymerization (alternatively made by polymerizing aminocaproic acid). The peptide bond within the caprolactam is broken with the exposed active groups on each side being incorporated into two new bonds as the monomer becomes part of the polymer backbone. In this case, all amide bonds lie in the same direction, but the properties of nylon 6 are sometimes indistinguishable from those of nylon 6,6 — except for melt temperature and some fiber properties in products like carpets and textiles. There is also nylon 9.
The 428 °F (220 °C) melting point of nylon 6 is lower than the 509 °F (265 °C) melting point of nylon 6,6.
Nylon 5,10, made from pentamethylene diamine and sebacic acid, was studied by Carothers even before nylon 6,6 and has superior properties, but is more expensive to make. In keeping with this naming convention, "nylon 6,12" (N-6,12) or "PA-6,12" is a copolymer of a 6C diamine and a 12C diacid. Similarly for N-5,10 N-6,11; N-10,12, etc. Other nylons include copolymerized dicarboxylic acid/diamine products that are not based upon the monomers listed above. For example, some aromatic nylons are polymerized with the addition of diacids like terephthalic acid (? Kevlar Twaron) or isophthalic acid (? Nomex), more commonly associated with polyesters. There are copolymers of N-6,6/N6; copolymers of N-6,6/N-6/N-12; and others. Because of the way polyamides are formed, nylon would seem to be limited to unbranched, straight chains. But "star" branched nylon can be produced by the condensation of dicarboxylic acids with polyamines having three or more amino groups.
Concepts of nylon production
The first approach: combining molecules with an acid (COOH) group on each end are reacted with two chemicals that contain amine (NH2) groups on each end. This process creates nylon 6,6, made of hexamethylene diamine with six carbon atoms and adipic acid.
The second approach: a compound has an acid at one end and an amine at the other and is polymerized to form a chain with repeating units of (-NH-[CH2]n-CO-)x. In other words, nylon 6 is made from a single six-carbon substance called caprolactam. In this equation, if n=5, then nylon 6 is the assigned name (may also be referred to as polymer).
The characteristic features of nylon 6,6 include:
Pleats and creases can be heat-set at higher temperatures
More compact molecular structure
Better weathering properties; better sunlight resistance
Softer "Hand"
Higher melting point (256 °C / 492.8 °F)
Superior colorfastness
Excellent abrasion resistance
On the other hand, nylon 6 is easy to dye, more readily fades; it has a higher impact resistance, a more rapid moisture absorption, greater elasticity and elastic recovery.
Characteristics
Variation of luster: nylon has the ability to be very lustrous, semilustrous or dull.
Durability: its high tenacity fibers are used for seatbelts, tire cords, ballistic cloth and other uses.
High elongation
Excellent abrasion resistance
Highly resilient (nylon fabrics are heat-set)
Paved the way for easy-care garments
High resistance to insects, fungi, animals, as well as molds, mildew, rot and many chemicals
Used in carpets and nylon stockings
Melts instead of burning
Used in many military applications
Good specific strength
Transparent under infrared light (-12dB)
Bulk properties
Above their melting temperatures, Tm, thermoplastics like nylon are amorphous solids or viscous fluids in which the chains approximate random coils. Below Tm, amorphous regions alternate with regions which are lamellar crystals. The amorphous regions contribute elasticity and the crystalline regions contribute strength and rigidity. The planar amide (-CO-NH-) groups are very polar, so nylon forms multiple hydrogen bonds among adjacent strands. Because the nylon backbone is so regular and symmetrical, especially if all the amide bonds are in the trans configuration, nylons often have high crystallinity and make excellent fibers. The amount of crystallinity depends on the details of formation, as well as on the kind of nylon. Apparently it can never be quenched from a melt as a completely amorphous solid.
Nylon 6,6 can have multiple parallel strands aligned with their neighboring peptide bonds at coordinated separations of exactly 6 and 4 carbons for considerable lengths, so the carbonyl oxygens and amide hydrogens can line up to form interchain hydrogen bonds repeatedly, without interruption. Nylon 5,10 can have coordinated runs of 5 and 8 carbons. Thus parallel (but not antiparallel) strands can participate in extended, unbroken, multi-chain ?-pleated sheets, a strong and tough supermolecular structure similar to that found in natural silk fibroin and the ?-keratins in feathers. (Proteins have only an amino acid ?-carbon separating sequential -CO-NH- groups.) Nylon 6 will form uninterrupted H-bonded sheets with mixed directionalities, but the ?-sheet wrinkling is somewhat different. The three-dimensional disposition of each alkane hydrocarbon chain depends on rotations about the 109.47° tetrahedral bonds of singly-bonded carbon atoms.
When extruded into fibers through pores in an industrial spinneret, the individual polymer chains tend to align because of viscous flow. If subjected to cold drawing afterwards, the fibers align further, increasing their crystallinity, and the material acquires additional tensile strength. In practice, nylon fibers are most often drawn using heated rolls at high speeds.
Block nylon tends to be less crystalline, except near the surfaces due to shearing stresses during formation. Nylon is clear and colorless, or milky, but is easily dyed. Multistranded nylon cord and rope is slippery and tends to unravel. The ends can be melted and fused with a heat source such as a flame or electrode to prevent this.
When dry, polyamide is a good electrical insulator. However, polyamide is hygroscopic. The absorption of water will change some of the material's properties such as its electrical resistance. Nylon is less absorbent than wool or cotton.
Historical uses
Bill Pittendreigh, DuPont, and other individuals and corporations worked diligently during the first few months of World War II to find a way to replace Asian silk and hemp with nylon in parachutes. It was also used to make tires, tents, ropes, ponchos, and other military supplies. It was even used in the production of a high-grade paper for U.S. currency. At the outset of the war, cotton accounted for more than 80% of all fibers used and manufactured, and wool fibers accounted for the remaining 20%. By August 1945, manufactured fibers had taken a market share of 25% and cotton had dropped.
Some of the terpolymers based upon nylon are used every day in packaging. Nylon has been used for meat wrappings and sausage sheaths.
Use in composites
Nylon can be used as the matrix material in composite materials, with reinforcing fibres like glass or carbon fiber; such a composite has a higher density than pure nylon. Such thermoplastic composites (25% glass fibre) are frequently used in car components next to the engine, such as intake manifolds, where the good heat resistance of such materials makes them feasible competitors to metals.
Hydrolysis and degradation
All nylons are susceptible to hydrolysis, especially by strong acids, a reaction essentially the reverse of the synthetic reaction shown above. The molecular weight of nylon products so attacked drops fast, and cracks form quickly at the affected zones. Lower members of the nylons (such as nylon 6) are affected more than higher members such as nylon 12. This means that nylon parts cannot be used in contact with sulfuric acid for example, such as the electrolyte used in lead-acid batteries. When being molded, nylon must be dried to prevent hydrolysis in the molding machine barrel since water at high temperatures can also degrade the polymer. The reaction is of the type:
Incineration and recycling
Various nylons break down in fire and form hazardous smoke, and toxic fumes or ash, typically containing hydrogen cyanide. Incinerating nylons to recover the high energy used to create them is usually expensive, so most nylons reach the garbage dumps, decaying very slowly. Some recycling is done on nylon, usually creating pellets for reuse in the industry, but this is done at a much lower scale
Etymology
In 1940, John W. Eckelberry of DuPont stated that the letters "nyl" were arbitrary and the "on" was copied from the suffixes of other fibers such as cotton and rayon. A later publication by DuPont explained that the name was originally intended to be "No-Run" ("run" meaning "unravel"), but was modified to avoid making such an unjustified claim and to make the word sound better. An apocryphal tale is that Nylon is a conflation of "New York" and "London". Equally spurious is the backronym for "Now You've Lost, Old Nippon" referring to the supposed loss of demand for Japanese silk.
Polyester
Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate (PET). Polyesters include naturally-occurring chemicals, such as in the cutin of plant cuticles, as well as synthetics through step-growth polymerization such as polycarbonate and polybutyrate. Natural polyesters and a few synthetic ones are biodegradable, but most synthetic polyesters are not.
Depending on the chemical structure polyester can be a thermoplastic or thermoset, however the most common polyesters are thermoplastics.
Fabrics woven from polyester thread or yarn are used extensively in apparel and home furnishings, from shirts and pants to jackets and hats, bed sheets, blankets and upholstered furniture. Industrial polyester fibers, yarns and ropes are used in tyre reinforcements, fabrics for conveyor belts, safety belts, coated fabrics and plastic reinforcements with high-energy absorption. Polyester fiber is used as cushioning and insulating material in pillows, comforters and upholstery padding.
While synthetic clothing in general is perceived by many as having a less-natural feel compared to fabrics woven from natural fibres (such as cotton and wool), polyester fabrics can provide specific advantages over natural fabrics, such as improved wrinkle resistance, durability and high color retention. As a result, polyester fibres are sometimes spun together with natural fibres to produce a cloth with blended properties. Synthetic fibres also can create materials with superior water, wind and environmental resistance compared to plant-derived fibres.
Polyesters are also used to make "plastic" bottles, films, tarpaulin, canoes, liquid crystal displays, holograms, filters, dielectric film for capacitors, film insulation for wire and insulating tapes.
Liquid crystalline polyesters are among the first industrially-used liquid crystal polymers. They are used for their mechanical properties and heat-resistance. These traits are also important in their application as an abradable seal in jet engines.
Polyesters are widely used as a finish on high-quality wood products such as guitars, pianos and vehicle/yacht interiors. Burns Guitars, Rolls Royce and Sunseeker are a few companies that use polyesters to finish their products. Thixotropic properties of spray-applicable polyesters make them ideal for use on open-grain timbers, as they can quickly fill wood grain, with a high-build film thickness per coat. Cured polyesters can be sanded and polished to a high-gloss, durable finish.
Types
Polyesters as thermoplastics may change shape after the application of heat. While combustible at high temperatures, polyesters tend to shrink away from flames and self-extinguish upon ignition. Polyester fibres have high tenacity and E-modulus as well as low water absorption and minimal shrinkage in comparison with other industrial fibres.
Unsaturated polyesters (UPR) are thermosetting resins. They are used as casting materials, fiberglass laminating resins and non-metallic auto-body fillers. Fibreglass-reinforced unsaturated polyesters find wide application in bodies of yachts and as body parts of cars.
Increasing the aromatic parts of polyesters increases their glass transition temperature, melting temperature, thermal stability, chemical stability...
Polyesters can also be telechelic oligomers like the polycaprolactone diol (PCL) and the polyethylene adipate diol (PEA). They are then used as prepolymers.
Industry
Basics
Polyester is a synthetic polymer made of purified terephthalic acid (PTA) or its dimethyl ester dimethyl terephthalate (DMT) and monoethylene glycol (MEG). With 18% market share of all plastic materials produced, it ranges third after polyethylene (33.5%) and polypropylene (19.5%).
The main raw materials are described as follows:
Purified terephthalic acid – PTA – CAS-No.: 100-21-0
Synonym: 1,4 benzenedicarboxylic acid,
Sum formula; C6H4(COOH)2 , mol weight: 166.13
Dimethylterephthalate – DMT – CAS-No: 120-61-6
Synonym: 1,4 benzenedicarboxylic acid dimethyl ester
Sum formula C6H4(COOCH3)2 , mol weight: 194.19
Mono Ethylene Glycol – MEG – CAS No.: 107-21-1
Synonym: 1,2 ethanediol
Sum formula: C2H6O2 , mol weight: 62,07
To make a polymer of high molecular weight a catalyst is needed. The most common catalyst is antimony trioxide (or antimony tri acetate):
Antimony trioxide – ATO – CAS-No.: 1309-64-4 Molecular weight: 291.51 Sum formula: Sb2O3
In 2008, about 10,000 tonnes Sb2O3 were used to produce around 49 million tonnes polyethylene terephthalate.
Polyester is described as follows:
Polyethylene Terephthalate CAS-No.: 25038-59-9 Synonym/abbreviations: polyester, PET, PES Sum Formula: H-[C10H8O4]-n=60–120 OH, molelcular unit weight: 192.17
There are several reasons for the importance of Polyester:
The relatively easy accessible raw materials PTA or DMT and MEG
The very well understood and described simple chemical process of polyester synthesis
The low toxicity level of all raw materials and side products during polyester production and processing
The possibility to produce PET in a closed loop at low emissions to the environment
The outstanding mechanical and chemical properties of polyester
The recyclability
The wide variety of intermediate and final products made of polyester.
In table 1 the estimated world polyester production is shown. Main applications are textile polyester, bottle polyester resin, film polyester mainly for packaging and specialty polyesters for engineering plastics. According to this table, the world's total polyester production might exceed 50 million tons per annum before the year 2010.
Table 1: World polyester production
Market size per year Product type 2002 [Million tonnes/year] 2008 [Million tonnes/year]
Textile-PET 20 39
Resin, bottle/A-PET 9 16
Film-PET 1.2 1.5
Special polyester 1 2.5
Total 31.2 49
Raw material producerThe raw materials PTA, DMT, and MEG are mainly produced by large chemical companies which are sometimes integrated down to the crude oil refinery where p-Xylene is the base material to produce PTA and liquefied petroleum gas (LPG) is the base material to produce MEG. Large PTA producers are for instance BP, Reliance, Sinopec, SK-Chemicals, Mitsui, and Eastman Chemicals. MEG production is in the hand of about 10 global players which are headed by MEGlobal a JV of DOW and PIC Kuweit followed by Sabic.
Polyester processingAfter the first stage of polymer production in the melt phase, the product stream divides into two different application areas which are mainly textile applications and packaging applications. In figure 2 the main applications of textile and packaging polyester are listed.
Table 2: Textile and packaging polyester application list
Polyester-based polymer (melt or pellet) Textile Packaging
Staple fiber (PSF) Bottles for CSD, Water, Beer, Juice, Detergents
Filaments POY, DTY, FDY A-PET Film
Technical yarn and tire cord Thermoforming
Non-woven and spunbond BO-PET Biaxial oriented Film
Mono-filament Strapping
Abbreviations: PSF = Polyester Staple Fiber; POY = Partially Oriented Yarn; DTY = Draw Textured Yarn; FDY = Fully Drawn Yarn; CSD = Carbonated Soft Drink; A-PET = Amorphous Polyester Film; BO-PET = Biaxial Oriented Polyester Film;
A comparable small market segment (much less than 1 million tonnes/year) of polyester is used to produce engineering plastics and masterbatch.
In order to produce the polyester melt with a high efficiency, high-output processing steps like staple fiber (50–300 tonnes/day per spinning line) or POY /FDY (up to 600 tonnes/day split into about 10 spinning machines) are meanwhile more and more horizontal, integrated, direct processes. This means the polymer melt is directly converted into the textile fibers or filaments without the common step of pelletizing. We are talking about full horizontal integration when polyester is produced at one site starting from crude oil or distillation products in the chain oil ? benzene ? PX ? PTA ? PET melt ? fiber/filament or bottle-grade resin. Such integrated processes are meanwhile established in more or less interrupted processes at one production site. Eastman Chemicals introduced at first the idea to close the chain from PX to PET resin with their so-called INTEGREX process. The capacity of such horizontal, integrated productions sites is >1000 tonnes/day and can easily reach 2500 tonnes/day.
Besides the above mentioned large processing units to produce staple fiber or yarns, there are ten thousands of small and very small processing plants, so that one can estimate that polyester is processed and recycled in more than 10 000 plants around the globe. This is without counting all the companies involved in the supply industry, beginning with engineering and processing machines and ending with special additives, stabilizers and colors. This is a gigantic industry complex and it is still growing by 4–8% per annum, depending on the world region. Useful information about the polyester industry can be found under where a “Who is Producing What in the Polyester Industry” is gradually being developed.
Polyester (1953)
Carbon fiber (1968)
Specialty synthetic fibers include:
Vinyon (1939)
Saran (1941)
Spandex (1959)
Vinalon (1939)
Aramids (1961) - known as Nomex, Kevlar and Twaron
Modal (1960's)
Dyneema/Spectra (1979)
PBI (Polybenzimidazole fiber) (1983)
Sulfar (1983)
Lyocell (1992)
PLA (2002)
M-5 (PIPD fiber)
Orlon
Zylon (PBO fiber)
Vectran (TLCP fiber) made from Vectra LCP polymer
Derclon used in manufacture of rugs
Other synthetic materials used in fibers include:
Acrylonitrile rubber (1930)
Modern fibers that are made from older artificial materials include:
Glass Fiber (1938) is used for:
industrial, automotive, and home insulation (Glass wool)
reinforcement of composite materials (Glass-reinforced plastic, Glass fiber reinforced concrete)
specialty papers in battery separators and filtration
Metallic fiber (1946) is used for:
adding metallic properties to clothing for the purpose of fashion (usually made with composite plastic and metal foils)
elimination and prevention of static charge build-up
conducting electricity to transmit information
conduction of heat
In the horticulture industry synthetics are often used in soils to help the plants grow better. Examples are:
expanded polystyrene flakes
urea-formaldehyde foam resin
polyurethane foam
phenolic resin foam
Industry structureDuring the last quarter of 20th century, Asian share of global output of synthetic fibers doubled to 65 per cent.
Synthesis
Synthesis of polyesters is generally achieved by a polycondensation reaction. See "condensation reactions in polymer chemistry". The general equation for the reaction of a diol with a diacid is :
(n+1) R(OH)2 + n R´(COOH)2 ? HO[ROOCR´COO]nROH + 2n H2O
[edit] Azeotrope esterificationIn this classical method, an alcohol and a carboxylic acid react to form a carboxylic ester. To assemble a polymer, the water formed by the reaction must be continually removed by azeotrope distillation.
Acylation (HCl method)The acid begins as an acid chloride, and thus the polycondensation proceeds with emission of hydrochloric acid (HCl) instead of water. This method can be carried out in solution or as an enamel.
Silyl method
In this variant of the HCl method, the carboxylic acid chloride is converted with the trimethyl silyl ether of the alcohol component and production of trimethyl silyl chloride is obtained
Acetate method (esterification)
Silyl acetate method
Ring-opening polymerization
Aliphatic polyesters can be assembled from lactones under very mild conditions, catalyzed anionically, cationically or metallorganically.
Cross-linking
Unsaturated polyesters are thermosetting resins. They are generally copolymers prepared by polymerizing one or more diol with saturated and unsaturated dicarboxylic acids (maleic acid, fumaric acid...) or their anhydrides. The double bond of unsaturated polyesters reacts with a vinyl monomer mainly the styrene, resulting in a 3-D cross-linked structure. This structure acts as a thermoset. The cross-linking is initiated through an exothermic reaction involving an organic peroxide, such as methyl ethyl ketone peroxide or benzoyl peroxide.
Health effects
A study published in 1993 found that polyester underwear reduced sperm count and sperm motility in male dogs. Similar studies have shown similar results in humans and rats. The cause is not known but is believed to be due to an electrostatic field created by the fabric.
Synthetic and artificial fiber
Image by Joost J. Bakker IJmuiden
Synthetic and artificial fiber
Synthetic fibers are the result of extensive research by scientists to improve on naturally occurring animal and plant fibers. In general, synthetic fibers are created by forcing, usually through extrusion, fiber forming materials through holes (called spinnerets) into the air, forming a thread. Before synthetic fibers were developed, artificially manufactured fibers were made from cellulose, which comes from plants. These fibers are called cellulose fibers.
Synthetic fibers account for about half of all fiber usage, with applications in every field of fiber and textile technology. Although many classes of fiber based on synthetic polymers have been evaluated as potentially valuable commercial products, four of them - nylon, polyester, acrylic and polyolefin - dominate the market. These four account for approximately 98 per cent by volume of synthetic fiber production, with polyester alone accounting for around 60 per cent.
HistoryThe first artificial fiber, known as artificial silk, became known as viscose around 1894, and finally rayon in 1924. A similar product known as cellulose acetate was discovered in 1865. Rayon and acetate are both artificial fibers, but not truly synthetic, being made from wood. Although these artificial fibers were discovered in the mid-nineteenth century, successful modern manufacture began much later (see the dates below).
Nylon, the first synthetic fiber, made its debut in the United States as a replacement for silk, just in time for World War II rationing. Its novel use as a material for women's stockings overshadowed more practical uses, such as a replacement for the silk in parachutes and other military uses.
Common synthetic fibers include:
Rayon (1910) (artificial, not synthetic)
Acetate (1924) (artificial, not synthetic)
Nylon (1939)
Modacrylic (1949)
Olefin (1949)
Acrylic (1950)
Rayon
Rayon is a manufactured regenerated cellulose fiber. Because it is produced from naturally occurring polymers, it is neither a truly synthetic fiber nor a natural fiber; it is a semi-synthetic or artificial fiber. Rayon is known by the names viscose rayon and art silk in the textile industry. It usually has a high luster quality giving it a bright sheen.
Uses
Some major rayon fiber uses include apparel (e.g. blouses, dresses, jackets, lingerie, linings, scarves, suits, neckties, hats, socks), the filling in Zippo lighters, furnishings (e.g. bedspreads, bedsheets, blankets, window treatments, upholstery, slipcovers), industrial uses (e.g. medical surgery products, non-woven products, tire cord), and other uses (e.g. yarn, feminine hygiene products, diapers, towels). Rayon is a major feedstock in the production of carbon fiber.
In early 2010, the U.S. Federal Trade Commission warned several retailers that six major manufacturers were falsely labeling rayon products as "bamboo", in order to appeal to environmentally conscious consumers. While rayon may be produced with bamboo as a raw material, and the two may be used for similar fabrics (though natural bamboo is not as smooth), rayon is so far removed from bamboo by chemical processing that the two are entirely separate.
History
NitrocelluloseThe fact that nitrocellulose is soluble in organic solvents such as ether and acetone, made it possible for Georges Audemars to develop the first "artificial silk" about 1855, but his method was impractical for commercial use. Commercial production started in 1891, but the result was flammable, and more expensive than acetate or cuprammonium rayon. Because of this, production was stopped before World War I, for example in 1912 in Germany. Briefly, it became known as "mother-in-law silk."
Nathan Rosenstein invented the spunize process by which he turned rayon from a hard fiber to a fabric. This allowed rayon to become a popular raw material in textiles.
Acetate method
Paul Schützenberger discovered that cellulose can be reacted with acetic anhydride to form cellulose acetate. The triacetate is only[citation needed] soluble in chloroform making the method expensive. The discovery that hydrolyzed cellulose acetate is soluble in more polar solvents, like acetone, made production of cellulose acetate fibers cheap and efficient.
Cuprammonium method
The German chemist Eduard Schweizer discovered that tetraaminecopper dihydroxide could dissolve cellulose. Max Fremery and Johann Urban developed a method to produce carbon fibers for use in light bulbs in 1897. Production of rayon for textiles started in 1899 in the Vereinigte Glanzstofffabriken AG in Oberbruch. Improvement[citation needed] by the J.P. Bemberg AG in 1904 made the artificial silk a product comparable to real silk.
Viscose method
Finally, in 1894, English chemist Charles Frederick Cross, and his collaborators Edward John Bevan, and Clayton Beadle patented their artificial silk, which they named "viscose", because the reaction product of carbon disulfide and cellulose in basic conditions gave a highly viscous solution of xanthate. The first commercial viscose rayon was produced by the UK company Courtaulds Fibers in 1905. Avtex Fibers Incorporated began selling their formulation in the United States in 1910. The name "rayon" was adopted in 1924, with "viscose" being used for the viscous organic liquid used to make both rayon and cellophane. In Europe, though, the fabric itself became known as "viscose," which has been ruled an acceptable alternative term for rayon by the U.S. Federal Trade Commission. The method is able to use wood (cellulose and lignin) as a source of cellulose while the other methods need lignin-free cellulose as starting material. This makes it cheaper and therefore it was used on a larger scale than the other methods.
Contamination of the waste water by carbon disulfide, lignin and the xanthates made this process detrimental to the environment. Rayon was only produced as a filament fiber until the 1930s when it was discovered that broken waste rayon could be used in staple fiber.
The physical properties of rayon were unchanged until the development of high-tenacity rayon in the 1940s. Further research and development led to the creation of high-wet-modulus rayon (HWM rayon) in the 1950s.. Research in the UK was centred on the government-funded British Rayon Research Association.
Major fiber properties
Rayon is a very versatile fiber and has the same comfort properties as natural fibers. It can imitate the feel and texture of silk, wool, cotton and linen. The fibers are easily dyed in a wide range of colors. Rayon fabrics are soft, smooth, cool, comfortable, and highly absorbent, but they do not insulate body heat, making them ideal for use in hot and humid climates. The highest quality Hawaiian shirts produced between the 1930s and the 1950s that are most sought after by collectors are all made of rayon.
The durability and appearance retention of regular rayon are low, especially when wet; also, rayon has the lowest elastic recovery of any fiber. However, HWM rayon is much stronger and exhibits higher durability and appearance retention. Recommended care for regular rayon is dry-cleaning only. HWM rayon can be machine washed.
Physical structure
Regular rayon has lengthwise lines called striations and its cross-section is an indented circular shape. The cross-sections of HWM and cupra rayon are rounder. Filament rayon yarns vary from 80 to 980 filaments per yarn and vary in size from 40 to 5000 denier. Staple fibers range from 1.5 to 15 denier and are mechanically or chemically crimped. Rayon fibers are naturally very bright, but the addition of delustering pigments cuts down on this natural brightness.
Production method
Regular rayon (or viscose) is the most widely produced form of rayon. This method of rayon production has been utilized since the early 1900s and it has the ability to produce either filament or staple fibers. The process is as follows:
1.Cellulose: Production begins with processed cellulose
2.Immersion: The cellulose is dissolved in caustic soda: (C6H10O5)n + nNaOH ? (C6H9O4ONa)n + nH2O
3.Pressing: The solution is then pressed between rollers to remove excess liquid
4.White Crumb: The pressed sheets are crumbled or shredded to produce what is known as "white crumb"
5.Aging: The "white crumb" aged through exposure to oxygen
6.Xanthation: The aged "white crumb" is mixed with carbon disulfide in a process known as Xanthation, the aged alkali cellulose crumbs are placed in vats and are allowed to react with carbon disulfide under controlled temperature (20 to 30°C) to form cellulose xanthate: (C6H9O4ONa)n + nCS2 ? (C6H9O4O-SC-SNa)n
7.Yellow Crumb: Xanthation changes the chemical makeup of the cellulose mixture and the resulting product is now called "yellow crumb"
8.Viscose: The "yellow crumb" is dissolved in a caustic solution to form viscose
9.Ripening: The viscose is set to stand for a period of time, allowing it to ripen: (C6H9O4O-SC-SNa)n + nH2O ? (C6H10O5)n + nCS2 + nNaOH
10.Filtering: After ripening, the viscose is filtered to remove any undissolved particles
11.Degassing: Any bubbles of air are pressed from the viscose in a degassing process
12.Extruding: The viscose solution is extruded through a spinneret, which resembles a shower head with many small holes
13.Acid Bath: As the viscose exits the spinneret, it lands in a bath of sulfuric acid, resulting in the formation of rayon filaments: (C6H9O4O-SC-SNa)n + ½nH2SO4 ? (C6H10O5)n + nCS2 + ½nNa2SO4
14.Drawing: The rayon filaments are stretched, known as drawing, to straighten out the fibers
15.Washing: The fibers are then washed to remove any residual chemicals
16.Cutting: If filament fibers are desired the process ends here. The filaments are cut down when producing staple fibers
High wet modulus rayon (HWM) is a modified version of viscose that has a greater strength when wet. It also has the ability to be mercerized like cotton. HWM rayons are also known as "polynosic" or can be identified by the trade name Modal.
High-tenacity rayon is another modified version of viscose that has almost twice the strength of HWM. This type of rayon is typically used for industrial purposes such as tire cord.
Cupramonium rayon has properties similar to viscose but during production, the cellulose is combined with copper and ammonia (Schweizer's reagent). Due to the environmental effects of this production method, cupramonium rayon is no longer produced in the United States.
Disposal and biodegradability
The biodegradability of fibers in soil burial and sewage sludge was evaluated by Korean researchers who found that biodegradability decreased in the following order: rayon, cotton, acetate (meaning rayon decays more readily than cotton). The ability of individual rayon-based fabrics to repel water was negatively correlated with their speed of degradation (meaning the greater the water-repelling ability of the fibre, the slower it will decompose).
Producers
Trade names are used within the rayon industry to determine the type of rayon used.
Look up Bemberg in Wiktionary, the free dictionary.
Bemberg, for example, is a trade name for cupramonium rayon developed by J.P. Bemberg that is now only produced in Italy due to United States Environmental Protection Agency regulations in the US.
Modal and Tencel are widely used forms of rayon produced by Lenzing Fibers Corp. which is based in northern Austria.
Galaxy, Danufil, and Viloft are rayon brands produced by Kelheim Fibres, a German manufacturer.
Acordis is a major manufacturer of cellulose based fibers and yarns. Production facilities can be found throughout Europe, the U.S. and Brazil.
Visil rayon is a flame retardant form of viscose which has silica embedded in the fiber during manufacturing.
North American Rayon Corp of Tennessee produced viscose rayon until its closure in the year 2000.
Grasim of India is the largest producer of rayon in the world (claiming 24% market share). It has plants in Nagda, Kharach and Harihar - all in India.
See also For a description of the production method at a factory in Germany in World War II, see pages 152-155 of
Agnès Humbert, (tr. Barbara Mellor) Résistance: Memoirs of Occupied France, London, Bloomsbury Publishing PLC, 2008 ISBN 9780747595977 (American title: Resistance: A Frenchwoman's Journal of the War, Bloomsbury, USA, 2008)
Nylon
Nylon is a generic designation for a family of synthetic polymers known generically as polyamides, first produced on February 28, 1935, by Wallace Carothers at DuPont's research facility at the DuPont Experimental Station. Nylon is one of the most commonly used polymers
Nylon is a thermoplastic silky material, first used commercially in a nylon-bristled toothbrush (1938), followed more famously by women's stockings ("nylons"; 1940). It is made of repeating units linked by amide bonds and is frequently referred to as polyamide (PA). Nylon was the first commercially successful synthetic polymer. There are two common methods of making nylon for fiber applications. In one approach, molecules with an acid (COOH) group on each end are reacted with molecules containing amine (NH2) groups on each end. The resulting nylon is named on the basis of the number of carbon atoms separating the two acid groups and the two amines. These are formed into monomers of intermediate molecular weight, which are then reacted to form long polymer chains.
Nylon was intended to be a synthetic replacement for silk and substituted for it in many different products after silk became scarce during World War II. It replaced silk in military applications such as parachutes and flak vests, and was used in many types of vehicle tires.
Nylon fibres are used in many applications, including fabrics, bridal veils, carpets, musical strings, and rope.
Solid nylon is used for mechanical parts such as machine screws, gears and other low- to medium-stress components previously cast in metal. Engineering-grade nylon is processed by extrusion, casting, and injection molding. Solid nylon is used in hair combs. Type 6,6 Nylon 101 is the most common commercial grade of nylon, and Nylon 6 is the most common commercial grade of molded nylon. Nylon is available in glass-filled variants which increase structural and impact strength and rigidity, and molybdenum sulfide-filled variants which increase lubricity.
Aramids are another type of polyamide with quite different chain structures which include aromatic groups in the main chain. Such polymers make excellent ballistic fibres.
Chemistry
Nylons are condensation copolymers formed by reacting equal parts of a diamine and a dicarboxylic acid, so that amides are formed at both ends of each monomer in a process analogous to polypeptide biopolymers. Chemical elements included are carbon, hydrogen, nitrogen, and oxygen. The numerical suffix specifies the numbers of carbons donated by the monomers; the diamine first and the diacid second. The most common variant is nylon 6-6 which refers to the fact that the diamine (hexamethylene diamine, IUPAC name: 1,6-diaminohexane) and the diacid (adipic acid, IUPAC name: hexane-1,6-dicarboxylic acid) each donate 6 carbons to the polymer chain. As with other regular copolymers like polyesters and polyurethanes, the "repeating unit" consists of one of each monomer, so that they alternate in the chain. Since each monomer in this copolymer has the same reactive group on both ends, the direction of the amide bond reverses between each monomer, unlike natural polyamide proteins which have overall directionality: C terminal ? N terminal. In the laboratory, nylon 6-6 can also be made using adipoyl chloride instead of adipic.
It is difficult to get the proportions exactly correct, and deviations can lead to chain termination at molecular weights less than a desirable 10,000 daltons (u). To overcome this problem, a crystalline, solid "nylon salt" can be formed at room temperature, using an exact 1:1 ratio of the acid and the base to neutralize each other. Heated to 285 °C (545 °F), the salt reacts to form nylon polymer. Above 20,000 daltons, it is impossible to spin the chains into yarn, so to combat this, some acetic acid is added to react with a free amine end group during polymer elongation to limit the molecular weight. In practice, and especially for 6,6, the monomers are often combined in a water solution. The water used to make the solution is evaporated under controlled conditions, and the increasing concentration of "salt" is polymerized to the final molecular weight.
DuPont patented[1] nylon 6,6, so in order to compete, other companies (particularly the German BASF) developed the homopolymer nylon 6, or polycaprolactam — not a condensation polymer, but formed by a ring-opening polymerization (alternatively made by polymerizing aminocaproic acid). The peptide bond within the caprolactam is broken with the exposed active groups on each side being incorporated into two new bonds as the monomer becomes part of the polymer backbone. In this case, all amide bonds lie in the same direction, but the properties of nylon 6 are sometimes indistinguishable from those of nylon 6,6 — except for melt temperature and some fiber properties in products like carpets and textiles. There is also nylon 9.
The 428 °F (220 °C) melting point of nylon 6 is lower than the 509 °F (265 °C) melting point of nylon 6,6.
Nylon 5,10, made from pentamethylene diamine and sebacic acid, was studied by Carothers even before nylon 6,6 and has superior properties, but is more expensive to make. In keeping with this naming convention, "nylon 6,12" (N-6,12) or "PA-6,12" is a copolymer of a 6C diamine and a 12C diacid. Similarly for N-5,10 N-6,11; N-10,12, etc. Other nylons include copolymerized dicarboxylic acid/diamine products that are not based upon the monomers listed above. For example, some aromatic nylons are polymerized with the addition of diacids like terephthalic acid (? Kevlar Twaron) or isophthalic acid (? Nomex), more commonly associated with polyesters. There are copolymers of N-6,6/N6; copolymers of N-6,6/N-6/N-12; and others. Because of the way polyamides are formed, nylon would seem to be limited to unbranched, straight chains. But "star" branched nylon can be produced by the condensation of dicarboxylic acids with polyamines having three or more amino groups.
Concepts of nylon production
The first approach: combining molecules with an acid (COOH) group on each end are reacted with two chemicals that contain amine (NH2) groups on each end. This process creates nylon 6,6, made of hexamethylene diamine with six carbon atoms and adipic acid.
The second approach: a compound has an acid at one end and an amine at the other and is polymerized to form a chain with repeating units of (-NH-[CH2]n-CO-)x. In other words, nylon 6 is made from a single six-carbon substance called caprolactam. In this equation, if n=5, then nylon 6 is the assigned name (may also be referred to as polymer).
The characteristic features of nylon 6,6 include:
Pleats and creases can be heat-set at higher temperatures
More compact molecular structure
Better weathering properties; better sunlight resistance
Softer "Hand"
Higher melting point (256 °C / 492.8 °F)
Superior colorfastness
Excellent abrasion resistance
On the other hand, nylon 6 is easy to dye, more readily fades; it has a higher impact resistance, a more rapid moisture absorption, greater elasticity and elastic recovery.
Characteristics
Variation of luster: nylon has the ability to be very lustrous, semilustrous or dull.
Durability: its high tenacity fibers are used for seatbelts, tire cords, ballistic cloth and other uses.
High elongation
Excellent abrasion resistance
Highly resilient (nylon fabrics are heat-set)
Paved the way for easy-care garments
High resistance to insects, fungi, animals, as well as molds, mildew, rot and many chemicals
Used in carpets and nylon stockings
Melts instead of burning
Used in many military applications
Good specific strength
Transparent under infrared light (-12dB)
Bulk properties
Above their melting temperatures, Tm, thermoplastics like nylon are amorphous solids or viscous fluids in which the chains approximate random coils. Below Tm, amorphous regions alternate with regions which are lamellar crystals. The amorphous regions contribute elasticity and the crystalline regions contribute strength and rigidity. The planar amide (-CO-NH-) groups are very polar, so nylon forms multiple hydrogen bonds among adjacent strands. Because the nylon backbone is so regular and symmetrical, especially if all the amide bonds are in the trans configuration, nylons often have high crystallinity and make excellent fibers. The amount of crystallinity depends on the details of formation, as well as on the kind of nylon. Apparently it can never be quenched from a melt as a completely amorphous solid.
Nylon 6,6 can have multiple parallel strands aligned with their neighboring peptide bonds at coordinated separations of exactly 6 and 4 carbons for considerable lengths, so the carbonyl oxygens and amide hydrogens can line up to form interchain hydrogen bonds repeatedly, without interruption. Nylon 5,10 can have coordinated runs of 5 and 8 carbons. Thus parallel (but not antiparallel) strands can participate in extended, unbroken, multi-chain ?-pleated sheets, a strong and tough supermolecular structure similar to that found in natural silk fibroin and the ?-keratins in feathers. (Proteins have only an amino acid ?-carbon separating sequential -CO-NH- groups.) Nylon 6 will form uninterrupted H-bonded sheets with mixed directionalities, but the ?-sheet wrinkling is somewhat different. The three-dimensional disposition of each alkane hydrocarbon chain depends on rotations about the 109.47° tetrahedral bonds of singly-bonded carbon atoms.
When extruded into fibers through pores in an industrial spinneret, the individual polymer chains tend to align because of viscous flow. If subjected to cold drawing afterwards, the fibers align further, increasing their crystallinity, and the material acquires additional tensile strength. In practice, nylon fibers are most often drawn using heated rolls at high speeds.
Block nylon tends to be less crystalline, except near the surfaces due to shearing stresses during formation. Nylon is clear and colorless, or milky, but is easily dyed. Multistranded nylon cord and rope is slippery and tends to unravel. The ends can be melted and fused with a heat source such as a flame or electrode to prevent this.
When dry, polyamide is a good electrical insulator. However, polyamide is hygroscopic. The absorption of water will change some of the material's properties such as its electrical resistance. Nylon is less absorbent than wool or cotton.
Historical uses
Bill Pittendreigh, DuPont, and other individuals and corporations worked diligently during the first few months of World War II to find a way to replace Asian silk and hemp with nylon in parachutes. It was also used to make tires, tents, ropes, ponchos, and other military supplies. It was even used in the production of a high-grade paper for U.S. currency. At the outset of the war, cotton accounted for more than 80% of all fibers used and manufactured, and wool fibers accounted for the remaining 20%. By August 1945, manufactured fibers had taken a market share of 25% and cotton had dropped.
Some of the terpolymers based upon nylon are used every day in packaging. Nylon has been used for meat wrappings and sausage sheaths.
Use in composites
Nylon can be used as the matrix material in composite materials, with reinforcing fibres like glass or carbon fiber; such a composite has a higher density than pure nylon. Such thermoplastic composites (25% glass fibre) are frequently used in car components next to the engine, such as intake manifolds, where the good heat resistance of such materials makes them feasible competitors to metals.
Hydrolysis and degradation
All nylons are susceptible to hydrolysis, especially by strong acids, a reaction essentially the reverse of the synthetic reaction shown above. The molecular weight of nylon products so attacked drops fast, and cracks form quickly at the affected zones. Lower members of the nylons (such as nylon 6) are affected more than higher members such as nylon 12. This means that nylon parts cannot be used in contact with sulfuric acid for example, such as the electrolyte used in lead-acid batteries. When being molded, nylon must be dried to prevent hydrolysis in the molding machine barrel since water at high temperatures can also degrade the polymer. The reaction is of the type:
Incineration and recycling
Various nylons break down in fire and form hazardous smoke, and toxic fumes or ash, typically containing hydrogen cyanide. Incinerating nylons to recover the high energy used to create them is usually expensive, so most nylons reach the garbage dumps, decaying very slowly. Some recycling is done on nylon, usually creating pellets for reuse in the industry, but this is done at a much lower scale
Etymology
In 1940, John W. Eckelberry of DuPont stated that the letters "nyl" were arbitrary and the "on" was copied from the suffixes of other fibers such as cotton and rayon. A later publication by DuPont explained that the name was originally intended to be "No-Run" ("run" meaning "unravel"), but was modified to avoid making such an unjustified claim and to make the word sound better. An apocryphal tale is that Nylon is a conflation of "New York" and "London". Equally spurious is the backronym for "Now You've Lost, Old Nippon" referring to the supposed loss of demand for Japanese silk.
Polyester
Polyester is a category of polymers which contain the ester functional group in their main chain. Although there are many polyesters, the term "polyester" as a specific material most commonly refers to polyethylene terephthalate (PET). Polyesters include naturally-occurring chemicals, such as in the cutin of plant cuticles, as well as synthetics through step-growth polymerization such as polycarbonate and polybutyrate. Natural polyesters and a few synthetic ones are biodegradable, but most synthetic polyesters are not.
Depending on the chemical structure polyester can be a thermoplastic or thermoset, however the most common polyesters are thermoplastics.
Fabrics woven from polyester thread or yarn are used extensively in apparel and home furnishings, from shirts and pants to jackets and hats, bed sheets, blankets and upholstered furniture. Industrial polyester fibers, yarns and ropes are used in tyre reinforcements, fabrics for conveyor belts, safety belts, coated fabrics and plastic reinforcements with high-energy absorption. Polyester fiber is used as cushioning and insulating material in pillows, comforters and upholstery padding.
While synthetic clothing in general is perceived by many as having a less-natural feel compared to fabrics woven from natural fibres (such as cotton and wool), polyester fabrics can provide specific advantages over natural fabrics, such as improved wrinkle resistance, durability and high color retention. As a result, polyester fibres are sometimes spun together with natural fibres to produce a cloth with blended properties. Synthetic fibres also can create materials with superior water, wind and environmental resistance compared to plant-derived fibres.
Polyesters are also used to make "plastic" bottles, films, tarpaulin, canoes, liquid crystal displays, holograms, filters, dielectric film for capacitors, film insulation for wire and insulating tapes.
Liquid crystalline polyesters are among the first industrially-used liquid crystal polymers. They are used for their mechanical properties and heat-resistance. These traits are also important in their application as an abradable seal in jet engines.
Polyesters are widely used as a finish on high-quality wood products such as guitars, pianos and vehicle/yacht interiors. Burns Guitars, Rolls Royce and Sunseeker are a few companies that use polyesters to finish their products. Thixotropic properties of spray-applicable polyesters make them ideal for use on open-grain timbers, as they can quickly fill wood grain, with a high-build film thickness per coat. Cured polyesters can be sanded and polished to a high-gloss, durable finish.
Types
Polyesters as thermoplastics may change shape after the application of heat. While combustible at high temperatures, polyesters tend to shrink away from flames and self-extinguish upon ignition. Polyester fibres have high tenacity and E-modulus as well as low water absorption and minimal shrinkage in comparison with other industrial fibres.
Unsaturated polyesters (UPR) are thermosetting resins. They are used as casting materials, fiberglass laminating resins and non-metallic auto-body fillers. Fibreglass-reinforced unsaturated polyesters find wide application in bodies of yachts and as body parts of cars.
Increasing the aromatic parts of polyesters increases their glass transition temperature, melting temperature, thermal stability, chemical stability...
Polyesters can also be telechelic oligomers like the polycaprolactone diol (PCL) and the polyethylene adipate diol (PEA). They are then used as prepolymers.
Industry
Basics
Polyester is a synthetic polymer made of purified terephthalic acid (PTA) or its dimethyl ester dimethyl terephthalate (DMT) and monoethylene glycol (MEG). With 18% market share of all plastic materials produced, it ranges third after polyethylene (33.5%) and polypropylene (19.5%).
The main raw materials are described as follows:
Purified terephthalic acid – PTA – CAS-No.: 100-21-0
Synonym: 1,4 benzenedicarboxylic acid,
Sum formula; C6H4(COOH)2 , mol weight: 166.13
Dimethylterephthalate – DMT – CAS-No: 120-61-6
Synonym: 1,4 benzenedicarboxylic acid dimethyl ester
Sum formula C6H4(COOCH3)2 , mol weight: 194.19
Mono Ethylene Glycol – MEG – CAS No.: 107-21-1
Synonym: 1,2 ethanediol
Sum formula: C2H6O2 , mol weight: 62,07
To make a polymer of high molecular weight a catalyst is needed. The most common catalyst is antimony trioxide (or antimony tri acetate):
Antimony trioxide – ATO – CAS-No.: 1309-64-4 Molecular weight: 291.51 Sum formula: Sb2O3
In 2008, about 10,000 tonnes Sb2O3 were used to produce around 49 million tonnes polyethylene terephthalate.
Polyester is described as follows:
Polyethylene Terephthalate CAS-No.: 25038-59-9 Synonym/abbreviations: polyester, PET, PES Sum Formula: H-[C10H8O4]-n=60–120 OH, molelcular unit weight: 192.17
There are several reasons for the importance of Polyester:
The relatively easy accessible raw materials PTA or DMT and MEG
The very well understood and described simple chemical process of polyester synthesis
The low toxicity level of all raw materials and side products during polyester production and processing
The possibility to produce PET in a closed loop at low emissions to the environment
The outstanding mechanical and chemical properties of polyester
The recyclability
The wide variety of intermediate and final products made of polyester.
In table 1 the estimated world polyester production is shown. Main applications are textile polyester, bottle polyester resin, film polyester mainly for packaging and specialty polyesters for engineering plastics. According to this table, the world's total polyester production might exceed 50 million tons per annum before the year 2010.
Table 1: World polyester production
Market size per year Product type 2002 [Million tonnes/year] 2008 [Million tonnes/year]
Textile-PET 20 39
Resin, bottle/A-PET 9 16
Film-PET 1.2 1.5
Special polyester 1 2.5
Total 31.2 49
Raw material producerThe raw materials PTA, DMT, and MEG are mainly produced by large chemical companies which are sometimes integrated down to the crude oil refinery where p-Xylene is the base material to produce PTA and liquefied petroleum gas (LPG) is the base material to produce MEG. Large PTA producers are for instance BP, Reliance, Sinopec, SK-Chemicals, Mitsui, and Eastman Chemicals. MEG production is in the hand of about 10 global players which are headed by MEGlobal a JV of DOW and PIC Kuweit followed by Sabic.
Polyester processingAfter the first stage of polymer production in the melt phase, the product stream divides into two different application areas which are mainly textile applications and packaging applications. In figure 2 the main applications of textile and packaging polyester are listed.
Table 2: Textile and packaging polyester application list
Polyester-based polymer (melt or pellet) Textile Packaging
Staple fiber (PSF) Bottles for CSD, Water, Beer, Juice, Detergents
Filaments POY, DTY, FDY A-PET Film
Technical yarn and tire cord Thermoforming
Non-woven and spunbond BO-PET Biaxial oriented Film
Mono-filament Strapping
Abbreviations: PSF = Polyester Staple Fiber; POY = Partially Oriented Yarn; DTY = Draw Textured Yarn; FDY = Fully Drawn Yarn; CSD = Carbonated Soft Drink; A-PET = Amorphous Polyester Film; BO-PET = Biaxial Oriented Polyester Film;
A comparable small market segment (much less than 1 million tonnes/year) of polyester is used to produce engineering plastics and masterbatch.
In order to produce the polyester melt with a high efficiency, high-output processing steps like staple fiber (50–300 tonnes/day per spinning line) or POY /FDY (up to 600 tonnes/day split into about 10 spinning machines) are meanwhile more and more horizontal, integrated, direct processes. This means the polymer melt is directly converted into the textile fibers or filaments without the common step of pelletizing. We are talking about full horizontal integration when polyester is produced at one site starting from crude oil or distillation products in the chain oil ? benzene ? PX ? PTA ? PET melt ? fiber/filament or bottle-grade resin. Such integrated processes are meanwhile established in more or less interrupted processes at one production site. Eastman Chemicals introduced at first the idea to close the chain from PX to PET resin with their so-called INTEGREX process. The capacity of such horizontal, integrated productions sites is >1000 tonnes/day and can easily reach 2500 tonnes/day.
Besides the above mentioned large processing units to produce staple fiber or yarns, there are ten thousands of small and very small processing plants, so that one can estimate that polyester is processed and recycled in more than 10 000 plants around the globe. This is without counting all the companies involved in the supply industry, beginning with engineering and processing machines and ending with special additives, stabilizers and colors. This is a gigantic industry complex and it is still growing by 4–8% per annum, depending on the world region. Useful information about the polyester industry can be found under where a “Who is Producing What in the Polyester Industry” is gradually being developed.
Polyester (1953)
Carbon fiber (1968)
Specialty synthetic fibers include:
Vinyon (1939)
Saran (1941)
Spandex (1959)
Vinalon (1939)
Aramids (1961) - known as Nomex, Kevlar and Twaron
Modal (1960's)
Dyneema/Spectra (1979)
PBI (Polybenzimidazole fiber) (1983)
Sulfar (1983)
Lyocell (1992)
PLA (2002)
M-5 (PIPD fiber)
Orlon
Zylon (PBO fiber)
Vectran (TLCP fiber) made from Vectra LCP polymer
Derclon used in manufacture of rugs
Other synthetic materials used in fibers include:
Acrylonitrile rubber (1930)
Modern fibers that are made from older artificial materials include:
Glass Fiber (1938) is used for:
industrial, automotive, and home insulation (Glass wool)
reinforcement of composite materials (Glass-reinforced plastic, Glass fiber reinforced concrete)
specialty papers in battery separators and filtration
Metallic fiber (1946) is used for:
adding metallic properties to clothing for the purpose of fashion (usually made with composite plastic and metal foils)
elimination and prevention of static charge build-up
conducting electricity to transmit information
conduction of heat
In the horticulture industry synthetics are often used in soils to help the plants grow better. Examples are:
expanded polystyrene flakes
urea-formaldehyde foam resin
polyurethane foam
phenolic resin foam
Industry structureDuring the last quarter of 20th century, Asian share of global output of synthetic fibers doubled to 65 per cent.
Synthesis
Synthesis of polyesters is generally achieved by a polycondensation reaction. See "condensation reactions in polymer chemistry". The general equation for the reaction of a diol with a diacid is :
(n+1) R(OH)2 + n R´(COOH)2 ? HO[ROOCR´COO]nROH + 2n H2O
[edit] Azeotrope esterificationIn this classical method, an alcohol and a carboxylic acid react to form a carboxylic ester. To assemble a polymer, the water formed by the reaction must be continually removed by azeotrope distillation.
Acylation (HCl method)The acid begins as an acid chloride, and thus the polycondensation proceeds with emission of hydrochloric acid (HCl) instead of water. This method can be carried out in solution or as an enamel.
Silyl method
In this variant of the HCl method, the carboxylic acid chloride is converted with the trimethyl silyl ether of the alcohol component and production of trimethyl silyl chloride is obtained
Acetate method (esterification)
Silyl acetate method
Ring-opening polymerization
Aliphatic polyesters can be assembled from lactones under very mild conditions, catalyzed anionically, cationically or metallorganically.
Cross-linking
Unsaturated polyesters are thermosetting resins. They are generally copolymers prepared by polymerizing one or more diol with saturated and unsaturated dicarboxylic acids (maleic acid, fumaric acid...) or their anhydrides. The double bond of unsaturated polyesters reacts with a vinyl monomer mainly the styrene, resulting in a 3-D cross-linked structure. This structure acts as a thermoset. The cross-linking is initiated through an exothermic reaction involving an organic peroxide, such as methyl ethyl ketone peroxide or benzoyl peroxide.
Health effects
A study published in 1993 found that polyester underwear reduced sperm count and sperm motility in male dogs. Similar studies have shown similar results in humans and rats. The cause is not known but is believed to be due to an electrostatic field created by the fabric.
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Forex trading?
Query by Mc D: Forex trading?
What are the risk of trading currency with Forex trading? I live in China, but needs to attempt trading currency with Forex. One particular of the operator asked me to send the funds across to them in USA and start off trading in minutes time. I don't know much about currency trading but they said they will offer you me a course to get me started. Do I engage in this organization?
Very best reply:
Reply by Common Sense
I am just finding into Foreign exchange trading. A trustworthy organization will tell you
9 out of 10 individuals that trade Forex shed their funds & give up.
Most Foreign exchange trades are losers.
Get into FX Trading if you're willing to take six months to a year understanding it. There are numerous techniques to discover (Books, on-line lessons etc.) Most FX brokers will allow you trade for totally free on a "Parctice Account". Often don't forget that outcomes are seldom the exact same the moment you begin "actual" trading.
If you have had some experiance in trading stocks or coomodities.... it could be a spot for you to get involved.
FX Is the largest trading platform in the world. It is unregulated. Be very very quite (very) mindful!
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gbp170311
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NO TRADE 16.03.eleven
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gbp220311
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Which company has the best reputation for currency (FOREX) trading?
Question by kaboodle777: Which business has the best reputation for currency (Forex) trading?
I'm interested in trading currencies with a Forex account, but I've also heard a lot of bad things about numerous companies. Does any person know which firm has the finest reputation for Forex trading?
Very best reply:
Answer by Glory
Wohoho, now you'll get the checklist - everyone will pull in its personal route... 
In reality, it is tough to solution, since there is no this kind of rating. If you appear at Forex brokers testimonials on-line, there is so significantly controversy in opinions and experiences, that you will almost certainly be lost.
Use the common sense and personal judgment. Of course, individuals businesses that are certainly labeled on the internet as scams should be avoided. For other folks, do a small of study: spend focus to the transparency of the business, by what authorities it is regulated, does it have adequate data describing the smallest facts about trading conditions, try their demo, attempt contacting them, see how properly they react. Do the identical issues as you would do when you pick a bank to deposit cash.
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Do I need to be registered and/or regulated by SEBI to provide forex trading tips?
Question by aura6677: Do I require to be registered and/or regulated by SEBI to provide foreign exchange trading guidelines?
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Answer by Kaspars S
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Which are the legitimate Forex Trading companies? Which is the authority registering these companies?
Question by sharafathin: Which are the respectable Foreign exchange Buying and selling companies? Which is the authority registering these firms?
I am looking for some legal Foreign exchange Trading companies to open account with. There are so several fraud firms in this field which are functioning with out registration and loots the public funds.. Also I want to know which is the authority providing regestration for these firms wherever the checklist of these regestered firms are published. Any physique please support me out!
Finest reply:
Answer by BS_Not_Here
When foreign exchange investing businesses can be in practically any nation, and you're really speaking about exchanging one currency for an additional, you really should presume that the regulation is minimal or nonexistent.
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At the internet site, they also supply forex trading educational material. In the backlinks I've added to this message, one particular is their web page for foreign exchange buying and selling, and the 2nd is the business history and data.
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