Textile Fibers

Overview of Fiber

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Fiber is a Hairlike Strand of material. It is a substance that is extremely long in relation to its width, at least 100 times longer than it is wide. A fiber is the smallest visible unit of any textile product. Fibers are flexible and may be spun into yarn and made into fabrics.

Commercially available fibers have diameters ranging from less than 0.004 mm (0.00015 in) to 0.2 mm (0.008 in) and they come in Several Different Forms:

Short Fibers (known as Staple or Chopped)

Continuous Single Fibers (Monofilament) Untwisted Bundles of Continuous Filaments (Tow)

Twisted Bundles of Continuous Filaments (Yarn)

Fibers are classified according to their origin, chemical structure, or both. They can be braided into ropes and cordage, made into felts (also called nonwovens), woven or knitted into textile fabrics, or, in the case of high-strength fibers, used as reinforcements in composites-that is, products made of two or more different materials

Fibers naturally occur in both plants and animals. More than half of the fibers produced are natural fibers. Natural fibers include cotton, hair, fur, silk, and wool. Other fibers are manufactured.

There are two types of manufactured fibers: Regenerated fibers and Synthetic fibers.
Regenerated fibers are made from natural materials by processing these materials to form a fiber structure. Also called cellulosics, regenerated fibers are derived from the cellulose in cotton and wood pulp. Rayon and acetate are two common regenerated fibers.Synthetic fibers are made entirely from chemicals.
Synthetic fibers are usually stronger than either natural or regenerated fibers. Synthetic fibers and the regenerated acetate fiber are thermoplastic; they are softened by heat. Therefore manufacturers can shape these fibers at high temperatures, adding such features as pleats and creases. Synthetic fibers will melt if touched with too hot an iron. The most widely used kinds of synthetic fibers are nylon (polyamide), polyester, acrylic, and olefin

Factors Affecting Fiber Quality

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There are many Factors that effect agro-fiber properties. For example,

* What part of the plant the fiber came from

* The age of the plant when the fiber was harvested

* How the fiber was isolated

* Permeability and hydroscopicity of the plant cell wall.

Fiber Length

The variability in fiber length can be explained primarily by genetics. Fiber elongation begins at bloom and continues for about 21 days.Starting with a variety that has better genetic potential for fiber length will minimize the probability of producing fiber length in the discount range.Moisture stress during this period will reduce fiber length in all varieties. Severe weathering after bolls have opened can reduce fiber length because more breakage can be expected in the ginning process.

Fiber Strength

Fiber strength is translated directly to yarn strength. In addition to producing stronger yarns, stronger fibers allow for faster and more efficient processing. Final strength level is achieved early in the fiber development stage; however, weathering can weaken the primary wall and cause strength levels to decline slightly in the weeks after boll opening.

Fiber strength is the most variety-dependent property. Any factor that causes either physical or microbial damage to the fiber can reduce strength. Severe drying at the gin also can reduce strength. The best management practice for fiber strength is variety selection, followed by sufficient potassium levels at the root zone in the soil.

Micronaire

Micronaire is determined both by fiber diameter and the amount of secondary wall development prior to boll opening. Micronaire is an indirect measure of both fiber maturity and fiber fineness (perimeter).

"There must be at least 100 fibers in the cross-section of yarn, so high micronaire fibers can become a limiting factor in spinning fine yarn.Fine fibers that are immature can break during processing and they do not dye well. This is why there are price discounts for both high and low micronaire. Fiber biological fineness is influenced by genetics, but environment and management can substantially affect fiber maturity.

Length Uniformity and Short Fiber Content

Length uniformity is now part of the premium/discount valuation of cotton. Short fibers within a process mix of cotton cannot wrap around each other and contribute little or nothing to yarn strength. Short fibers indirectly cause product defaults and directly contribute to higher waste and lower manufacturing efficiency.

Since short fiber content and length uniformity are derived from length, they are influenced by the same factors as length. Crop management practices that influence where bolls are located on the plant can impact short fiber content levels. Uniform fruit retention patterns encourage better length uniformity.

Color Grade

Both yellowness and brightness (reflectance) define color grade. Less total cellulose production during development can lead to lower brightness levels. The direct impact of color is in the bleaching process. Textile mills must control the color of their cotton within narrow limits to achieve a consistent fabric shade. Cotton loses some luster and brightness the longer it is subject to weathering.

Environmental factors account for 79 percent of the color variability in cottonr. When total rainfall after the cotton opens exceeds 2 inches, loss in color grade will occur. Discoloration can also be caused by the action of microorganisms in connection with boll rot or insect damage. Cotton stored in modules with moisture content above 11 percent, excessive trash, or improper covering can lead to reduction in color.

Leaf Grade

The amount of leaf grade is not a function of physical fiber development. While burs, stems or weed plant material can contribute to leaf grade, the major source of trash is leaf and bract material. Leaf grade has the most direct effect on manufacturing waste in the textile mill. Excessive leaf trash requires more cleaning and air-handling equipment, and impacts product quality.

Variety can impact leaf grade when there are differences in the amount of trichomes (hairiness) in the leaf and bract. Small bits of hairy leaves cling to fibers making their removal more difficult. High plant population, delayed maturity, excessive vegetative growth, lack of weed control and defoliation problems impact harvest efficiency and increase the amount of leaf in a bale.

Nylon Fiber Properties

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Density (g/cc) : 1.14

Moisture Regain(%) : 2.8 to 5.0

Elongationat Break(%) : 17 to 45

BreakingTenacity(g/Denier) : 4.0 to 7.2

InitialModulus(CN/tex) : 400

ThermalShrinkage(@ 177 C) : N/A

L.O.I. : ----

MeltingPoint (C/F) : 216/419

Fluorocarbon -Teflon® (PTFE) Properties

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Heat : Very heat resistant -350F to 550F. Melts at 620F.

Bleaches &Solvents : Essentially inert to bleaches & solvents

Acids & Alkalis : Excellent but effected by acids & alkali at high temperatures.

Abrasion : Good

Mildew, Aging &Sunlight : Excellent

Aramid(Kelvar®, Nomex®, Tarwon®, Technora®) Properties

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Heat : Difficult to ignite. Does not burn or melt. Decomposes at 800F to 932F.

Bleaches &Solvents : Poor in bleach.Excellent solvent resistance.

Acids & Alkalis : Good in dilute acids & bases. Poor in strong acids & bases.

Abrasion : Fair to Good

Mildew, Aging &Sunlight : Excellent resistance to mildew & aging. Degrades when exposed to sunlight.

Fiber Glass Properties

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Heat : Does not burn or melt

Bleaches &Solvents : Excellent solvent & bleach resistance.

Acids & Alkalis : Fair

Abrasion : Good

Mildew, Aging &Sunlight : Excellent

Spandez® / Lycra® Fiber Properties

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Heat : Sticks at 350-390F. Melts above 500F.

Bleaches &Solvents : Good resistance to oxidizing agents. Poor resistance to bleaches.

Acids & Alkalis : Good

Abrasion : Good in diluted (weak), but degrades in strong acids & bases.

Mildew, Aging &Sunlight : Excellent aging and mildew resistance. Good resistance to sunlight.

Polyethylene Fiber Properties

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Heat : Melts at 525F

Bleaches &Solvents : Excellent

Acids & Alkalis : Excellent

Abrasion : Good to Poor

Mildew, Aging &Sunlight : Excellent resistance to mildew.

Nylon Fibre Properties

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Heat : Melts at 419F to430F.

Bleaches &Solvents : Will bleach.Degrades in mineral acids & oxidizing agents.

Acids & Alkalis : Insoluble in organic solvents Resists weak acids, inert to alkalis. Hydrolyzed by strong acids

Abrasion : Excellent

Mildew, Aging &Sunlight : Excellent resistance to mildew and aging. Prolonged sun exposure can cause degradation.

Polyester Fiber Properties

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Heat :Melts at 500F.

Bleaches &Solvents : Excellent

Acids & Alkalis : Good resistance to weak alkalis & weak acids. Moderate resistance to strong acids & alkali.

Abrasion : Excellent

Mildew, Aging &Sunlight : Excellent resistance to mildew, good aging. Degrades after prolonged exposure to sunlight.

Fiber Testing

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Fiber Elongation

There are Three Types of Elongation

Permanent Elongation

The length which extended during loading did not recover during relaxation

Elastic Elongation

The extensions through which the fibres does return

Breaking Elongation

The maximum extension at which the yarn breaks i.e.permanent and elastic elongation together Elongation is specified as a percentage of the starting length. The elastic elongation is of deceisive importance, since textile products without elasticity would hardly be usable. They must be able to deforme, In order to withstand high loading, but they must also return to shatpe. The greater resistance to crease for wool compared to cotton arises, from the difference in their elongation. For cotton it is 6 -10% and for wool it is aroun 25 - 45%. For normal textile goods, higher elongation are neither necessary nor desirable. They make processing in the spinning mill more difficult, especially in drawing operations.

Fiber Rigidity

The Torsional rigidity of a fibre may be defined as the torque or twisting force required to twist 1 cm length of the fibre through 360 degrees and is proportional to the product of the modulus of rigidity and square of the area of cross-section, the constant of proportionality being dependent upon the shape of the cross-section of the fibre. The torsional rigidity of cotton has therefore been found to be very much dependent upon the gravimetric fineness of the fibres. As the rigidity of fibres is sensitive to the relative humidity of the surrounding atmosphere, it is essential that the tests are carried out in a conditional room where the relative humidity is kept constant.

The Slenderness Ratio

Fibre Stiffness plays a significant role mainly when rolling, revolving, twisting movements are involved. A fibre which is too stiff has difficulty adapting to the movements. It is difficult to get bound into the yarn, which results in higher hairiness. Fibres which are not stiff enough have too little springiness. They do not return to shape after deformation. They have no longitudinal resistance. In most cases this leads to formation of neps. Fibre stiffness is dependent upon fibre substance and also upon the relationship between fibre length and fibre fineness. Fibres having the same structure will be stiffer, the shorter they are. The slendernesss ratio can serve as a measure of stiffness
Slender Ratio = Fibre Length /Fibre Diameter
Since the fibres must wind as they are bound-in during yarn formation in the ring spinning machine, the slenderness ratio also determines to some extent where the fibres will finish up.fine and/or long fibres in the middle coarse and/or short fibres at the yarn periphery.

Trash Content

In additon to usuable fibres, cotton stock contains foreign matter of various kinds. This foreign material can lead to extreme disturbances during processing. Trash affects yarn and fabric quality. Cottons with two different trash contents should not be mixed together, as it will lead to processing difficulties. Optimising process paramters will be of great difficulty under this situation, therefore it is a must to know the amount of trash and the type of trash before deciding the mixing

Shirley Trash Analyser

A popular trash measuring device is the Shirley Analyser, which separates trash and foreign matter from lint by mechanical methods. The result is an expression of trash as a percentage of the combined weight of trash and lint of a sample. This instrument is used

To give the exact value of waste figures and also the proportion of clean cotton and trash in the material

To select the proper processing sequence based upon the trash content to assess the cleaning efficiency of each machine

To determine the loss of good fibre in the sequence of opening and cleaning.

Stricter sliver quality requirements led to the gradual evolution of opening and cleaning machinery leading to a situation where blow room and carding machinery were designed to remove exclusively certain specific types of trash particles. This necessitated the segregation of the trash in the cotton sample to different grades determined by their size. This was achieved in the instruments like the Trash Separator and the Micro Dust Trash Analyser which could be considered as modified versions of the Shirley Analyser.

The high volume instruments introduced the concept of optical methods of trash measurement which utilised video scanning trash-meters to identify areas darker than normal on a cotton sample surface. Here, the trash content was expressed as the percentage area covered by the trash particles. However in such methods, comparability with the conventional method could not be established in view of the non-uniform distribution of trash in a given cotton sample and the relatively smaller sample size to determine such a parameter. Consequently, it is yet to establish any significant name in the industry.

Quality Testing Instruments

Fibrogaph-Length

Pressley Apparatres-Fiber Bundle Strength

HV I Instrument- Length, Strength, Uniformity, Elongation, Micronaire, Color and Trash

Stelometer Instrument- Strength, Elongation

Micronaire -Combined test of fineness & maturity

Shirley Trash Analyser- Trash Content

Manual Test- Class & staple length

Colorimeter- Grey value & yellow ness,Brightness

Polarised light Microscope or Casricaire test -Maturity

Photographic film -Neppiness

Moisture Meter-Moisture

Microfiber

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Microfiber is fiber with strands less than one denier. Microfiber is a blend of polyester and polyamide. Fabrics made with microfibers are exceptionally soft and hold their shape well. When high quality microfiber is combined with the right knitting process, it creates an extremely effective cleaning material. This material can hold up to seven times its weight in water. They are also used for some cleaning applications, because of their exceptional ability to absorb oils.

Material of Microfiber

Microfiber is constructed in a blend of 80/20 ratio of polyester/polyamideams. They are made from a warp knitted thread, composed of wedge-shaped polyester filaments with a core of nylon. The fiber's wedge shaped filaments follow surfaces, lift up dirt, and then trap the particles inside the fibers. The capillary effect between the filaments and nylon core creates a high absorbency, which in turn enables this cloth to clean and polish at the same time.
To clean a microfiber cloth, wash with warm soapy water and rinse well. The warm water opens up the fibers, allowing them to release the locked in dirt. Placing the cloths in a washing machine and then drying them in a dryer on low heat is also effective. No fabric softeners of any kind should be used as the chemicals clog up the microfibers, making them less effective. Bleach should also be avoided as it corrodes the fibers over time, making them less effective. Ironing is also potentially damaging.

Functional Uses of Microfiber

Microfiber performance apparel has become a very popular alternative to cotton apparel for athletic wear, such as cycling jerseys, because the microfiber material wicks moisture away from the body, keeping the athlete cool and dry.

Microfiber materials, such as PrimaLoft are also used for thermal insulation as a replacement for down feather insulation in sleeping bags and outdoor equipment, due to its better retention of heat when damp or wet.

Fiber Blending

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The process of blending of different fibers into a single fabric is made to improve quality of this fabric and give it the desired properties. But long fibers cannot be used in that process, so they are being cut into smaller staple fibers and only after that they are blended into fabric. Some natural materials in their turn can be blended right away and do not need to be cut into smaller pieces.

Different sorts of natural fibers were used by people of all nations around the world for ages and various fabric weaving techniques allowed them to have different sorts of textile for making clothes. Later, with the development of chemical technologies the number of available materials has ballooned. In fact, new interesting materials are being developed now, so their number is constantly increasing

The production of manmade fibers is more cost effective than that of natural fibers, which is why synthetic fibers are in such great demand in the textile industry. There are two basic types of synthetic material. The first one contains cellulose (it forms cell walls in each plant; cellulose is mainly obtained from wood) like acetate silk, for example, while the other one does not contain any cellulose and is made entirely of chemical substances. And both types of fibers are made in more or less similar way. First of all, the components that are used to form fiber are turned into liquid form by means of solvents. Then this liquid is being squeezed through the very narrow device which is called a spinner. And at the same time thread, that is formed, is treated with special substances to be moulded into solid state. It is a rather uncomplicated process that allows reducing the price of fibers significantly. But still there are certain qualities of natural fibers that synthetic material is deprived of. The simple solution here is blending. Different synthetic materials can be combined with natural material and, thus, fabric will have qualities of both natural and synthetic fibers.

Purposes of Blending

There can be many different purposes of blending, but in most cases blending of different fibers is oriented on getting higher quality of fabrics. Mixing different sorts of fibers leads to better fabric characteristics that can be obtained. But not all sorts of fibers can be blended together, because different qualities of various materials are possible to reach only in certain combinations.

There are many different fibers that are used these days in making clothes and other products that involve cloth. The history of natural materials is pretty long. Fabric weaving has been known for more than 3000 years. The history of manmade fibers is not so impressive. These materials were invented not so long ago, but the quality of synthetic material is just great.

These wonderful qualities give manmade materials a huge range of different uses. They make our everyday life easier and in many professions synthetic materials can even save lives. These materials are also much cheaper in production than usual natural fibers that take a lot of time and efforts to be made. But not all qualities of manmade materials are that great and sometimes it is necessary to have better fabric characteristics.

Lyocell Rayon

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A new form of cellulosic fiber, Lyocell is starting to find uses in the nonwovens industry. Lyocell is manufactured using a solvent spinning process, and is produced by only two companies -- Acordis and Lenzing AG. To produce Lyocell, wood cellulose is dissolved directly in n-methyl morpholine n-oxide at high temperature and pressure. The cellulose precipitates in fiber form as the solvent is diluted, and can then be purified and dried. The solvent is recovered and reused. Lyocell has all the advantages of rayon, and in many respects is superior. It has high strength in both dry and wet states, high absorbency, and can fibrillate under certain conditions. In addition, the closed-loop manufacturing process is far more environmentally friendly than that used to manufacture rayon, although it is also more costly.

Tencel Rayon

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Unlike viscose rayon, Tencel is produced by a straight solvation process. Wood pulp is dissolved in an amine oxide, which does not lead to undue degradation of the cellulose chains. The clear viscous solution is filtered and extruded into an aqueous bath, which precipitates the cellulose as fibers. This process does not involve any direct chemical reaction and the diluted amine oxide is purified and reused. This makes for a completely contained process fully compatible with all environmental regulations.

Specialty Rayons

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Flame Retardant Fibers

Flame retardance is achieved by the adhesion of the correct flame- retardant chemical to viscose. Examples of additives are alkyl, aryl and halogenated alkyl or aryl phosphates, phosphazenes, phosphonates and polyphosphonates. Flame retardant rayons have the additives distributed uniformly through the interior of the fiber and this property is advantageous over flame retardant cotton fibers where the flame retardant concentrates at the surface of the fiber.

Super-Absorbent Rayons

This is being produced in order to obtain higher water retention capacity (although regular rayon retains as much as 100 % of its weight). These fibers are used in surgical nonwovens. These fibers are obtained by including water- holding polymers (such as sodium polyacrylate or sodium carboxy methyl cellulose) in the viscose prior to spinning, to get a water retention capacity in the range of 150 to 200 % of its weight.

Micro-Denier Fibers

Rayon fibers with deniers below 1.0 are now being developed and introduced into the market. These can be used to substantially improve fabric strength and absorbent properties.

Cross-Section Modification of Viscose Rayon

Modification in cross-sectional shape of viscose rayon can be used to dramatically change the fibers' aesthetic and technical properties. One such product is Viloft, a flat cross sectional fiber sold in Europe, which gives a unique soft handle, pleasing drape and handle. Another modified cross section fiber called Fibre ML(multi limbed) has a very well defined trilobal shape. Fabrics made of these fibers have considerably enhanced absorbency, bulk, cover and wet rigidity all of which are suitable for usage as nonwovens .

Polynosic Rayon

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Polynosic fibers have a very high degree of orientation, achieved as a result of very high stretching (up to 300 %) during processing. They have a unique fibrillar structure, high dry and wet strength, low elongation (8 to 11 %), relatively low water retention and very high wet modulus.

High Wet Modulus Rayon

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These fibers have exceptionally high wet modulus of about 1 g/den and are used as parachute cords and other industrial uses. Fortisan fibers made by Celanese (saponified acetate) has also been used for the same purpose

Cuprammonium Rayon

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Cuprammonium Rayon is produced by a solution of cellulosic material in cuprammonium hydroxide solution at low temperature in a nitrogen atmosphere, followed by extruding through a spinnerette into a sulphuric acid solution necessary to decompose cuprammonium complex to cellulose. This is a more expensive process than that of viscose rayon. Its fiber cross- section is almost round.

Acetate Rayon

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Cellulose acetate or acetate rayon fiber (1924) is one of the earliest synthetic fibers and is based on cotton or tree pulp cellulose ("biopolymers"). These "cellulosic fibers" have passed their peak as cheap petro-based fibers (nylon and polyester) and have displaced regenerated pulp fibers.

Acetate Fiber Characteristics

Cellulosic and thermoplastic

Selective absorption and removal of low levels of certain organic chemicals

Easily bonded with plasticizers, heat, and pressure

Acetate is soluble in many common solvents (especially acetone and other organic solvents) and can be modified to be soluble in alternative solvents, including water

Hydrophilic: acetate wets easily, with good liquid transport and excellent absorption; in textile applications, it provides comfort and absorbency, but also loses strength when wet

Acetate fibers are hypoallergenic

Major Industrial Acetate Fiber Uses

Apparel

Blouses, Dresses, Linings, Wedding and party attire, Home furnishings, Draperies, Upholstery and slip covers

High Absorbency Products

Diapers, Feminine Hygiene Products, Cigarette Filters, Surgical Products, and other filters

Production of Acetate Rayon

The Federal Trade Commission definition for acetate fiber is "A manufactured fiber in which the fiber-forming substance is cellulose acetate. Where not less than 92 percent of the hydroxyl groups are acetylated, the term triacetate may be used as a generic description of the fiber."

Acetate is derived from cellulose by deconstructing wood pulp into a purified fluffy white cellulose. The cellulose is then reacted with acetic acid and acetic anhydride in the presence of sulfuric acid. It is then put through a controlled, partial hydrolysis to remove the sulfate and a sufficient number of acetate groups to give the product the desired properties. The anhydroglucose unit is the fundamental repeating structure of cellulose and has three hydroxyl groups which can react to form acetate esters. The most common form of cellulose acetate fiber has an acetate group on approximately two of every three hydroxyls. This cellulose diacetate is known as secondary acetate, or simply as "acetate".

After it is formed, cellulose acetate is dissolved in acetone into a viscose resin for extrusion through spinnerets (which resemble a shower head). As the filaments emerge, the solvent is evaporated in warm air via dry spinning, producing fine cellulose acetate fibers.

Overview of Rayons

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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 fiber.

Rayon is known by the names viscose rayon and art silk in the textile industry. It usually has a high lustre quality giving it a bright shine. Rayon contains the chemical elements carbon, hydrogen, and oxygen

Carbon Fiber

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Manufacturing Process of Carbon Fiber

The conversion of PAN to carbon fibers is normally made in 4 continuous stages

Oxidation

Carbonisation(Graphitisation)

Surface treatment

Sizing

Uses of Carbon Fiber

Carbon fibers are used primarily in composites, these are structures containing two or more components, in the case of fiber reinforced composites this is the fiber and a resin. A composite containing two types of fiber, eg. carbon and glass, is known as a hybrid composite structure.

The origins of textile reinforced composites are linked to the development of glass fibers, which commenced in 1938 by the Owens Corning Fiberglass Corporation (USA). Original large scale applications included air filtration, thermal and electrical insulation and the reinforcement of plastics. As the technology of textile reinforced composites expanded, a growing demand from the aerospace industry for composite materials with superior properties emeged. In particular, materials with higher specific strength, higher specific moduli and low density were required. Other desirable properties are good fatigue resistance, and dimensional stability. Carbon fibers were developed to meet this demand.

Perlon Fiber

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Perlon was used as fabric for high pressure hose in airplane tires, as stiff bristles for cleaning weapons, for cords and ropes for parachutes - but also for lady´s stockings as a Christmas present for the wives of I.G.-Farben managers in 1943 and as reinforcement in socks used by the German armed forces. For the time being, the civil use of Perlon was unthinkable. Spinneret for the production of Perlon filaments. (Perlon is produced in the melt spinning process. The material is melted at high temperatures and continuously pressed through spinnerets by gear pumps. When cooled at room temperature, the mass congeals into fine filaments that can be pulled off and wound at a fast rate).

Teflon Fiber

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Teflon is the brand name of a polymer compound discovered by Roy J. Plunkett (1910-1994) of DuPont in 1938 and introduced as a commercial product in 1946. It is a thermoplastic fluoropolymer. Teflon is polytetrafluoroethylene (PTFE), a polymer of fluorinated ethylene.

Teflon is also used as the trade name for a polymer with similar properties, perfluoroalkoxy polymer resin (PFA)

PTFE has the lowest coefficient of friction of any known solid material. It is used as a non-stick coating for pans and other cookware. PTFE is very non-reactive, and so is often used in containers and pipework for reactive chemicals. Its melting point varies between 260 °C (FEP) and 327 °C (PTFE), depending on which specific Teflon polymer is being discussed.

PTFE is sometimes said to be a spin-off from the US space program with more down-to-earth applications; this is an urban legend, as teflon cooking pans were commonplace before Yuri Gagarin's flight in 1961. PTFE was discovered serendipitously by Roy Plunkett of DuPont in 1938, while attempting to make a new CFC refrigerant, when the perfluorethylene polymerized in its storage container. DuPont patented it in 1941, and registered the Teflon trademark in 1944.

An early advanced use was in the Manhattan Project, as a material to coat valves and seals in the pipes holding highly-reactive uranium hexafluoride in the vast Uranium enrichment plant at Oak Ridge, Tennessee, when it was known as K416.

It was first sold commercially in 1946 and by 1950, DuPont was producing over a million pounds (450 t) per year in Virginia.

Teflon has been supplemented with another DuPont product, Silverstone, a three-coat fluoropolymer system that produces a more durable finish than Teflon. Silverstone was released in 1976.

Amongst many other industrial applications, PTFE is used to coat certain types of hardened, armour-piercing bullets, so as to reduce the amount of wear on the firearm's rifling. These are often mistakenly referred to as "cop-killer" bullets on account of PTFE's supposed ability to ease a bullet's passage through body armour. Any armour-piercing effect is, however, purely a function of the bullet's velocity and rigidity rather than a property of PTFE.

PTFE is an excellent electrical insulator with good dielectric properties. This is especially true at high radio frequencies, making it eminently suitable for use as an insulator in cables and connector assemblies and as a material for printed circuit boards. Combined with its high melting temperature this makes it the material of choice as a high performance substitute for the weaker and more meltable polyethylene that is commonly used in low-cost applications.

Lyocell Fiber Characteristics

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Lyocell is a fibre made from wood pulp cellulose. It was first manufactured in 1992 by Acordis Cellulosic Fibers, Inc. The only current manufacturer in the United States is Tencel Ltd, who market it under the trademarked brand name Tencel.

The product is also manufactured by the Lenzing-based fiber manufacturer Lenzing AG, under the trademark Lenzing Lyocell. The Federal Trade Commission defines lyocell as "a cellulose fabric that is obtained by an organic solvent spinning process". It classifies the fibre as a sub-category of rayon. The fibre is used in the production of many clothes, such as jeans, trousers and coats