NYLON-RAYON-ACRYLIC

NYLON

Nylon Fibre- Overview Refers to family of polymers called linear polyamides

A manufactured fiber in which the fiber forming substance is a long-chain synthetic polyamide in which less than 85% of the amide-linkages are attached directly (-CO-NH-) to two aliphatic groups.

Two common varieties of nylon:

•Nylon 6.6-molecules with an acid (COOH) group on each end are reacted with molecules containing amine (NH2) groups on each end.

• Nylon 5- a compound containing an amine at one end and an acid at the other is polymerized to form a chain with repeating units of (-NH-[CH2]n-CO-)x

Production of nylon industrial and carpet fibers begins with an aqueous solution of monomers and proceeds continuously through polymerization, spinning, drawing, or draw-texturing.

Nylon Characteristics

Exceptionally strong

Elastic

Abrasion resistant

Lustrous

Easy to wash

Resistant to damage from oil and many chemicals

Can be precolored or dyed in wide range of colors Resilient

Low in moisture absorbency

Filament yarns provide smooth, soft, long-lasting fabrics

Spun yarns lend fabrics light weight and warmth

Uses of Nylon 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 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.

MODERN USES

Apparel: Blouses, dresses, foundation garments, hosiery, lingerie, underwear, raincoats, ski apparel, windbreakers, swimwear, and cycle wear

Home Furnishings: Bedspreads, carpets, curtains, upholstery

Industrial and Other Uses: Tire cord, hoses, conveyer and seat belts, parachutes, racket strings, ropes and nets, sleeping bags, tarpaulins, tents, thread, monofilament fishing line, dental floss

Nylon

Producers of Nylon

The producers of nylon include: Honeywell Nylon Inc., Invista, Wellman Inc. among many others. The Du pont Company, is the most famous pioneer of the nylon we know today

RAYON

Rayon- Overview

Rayon -oldest commercial manmade fibre.

Definition: A manufactured fiber composed of regenerated cellulose, in which substituent's have replaced not more than 15% of the hydrogen of the hydroxyl groups.

The process of making viscose was discovered by C.F.Cross and E.J.Bevan in 1891The process used to make viscose can be (a) Continuous Process (b) Batch Process

Three methods of production lead to distinctly different types of rayon fibers: viscose rayon, cuprammonium rayon and saponified cellulose acetate

Rayon Manufacturing Process

All of the early viscose production involved batch processing. In more recent times, processes have been modified to allow some semi-continuous production.

Steps involved :

CelluloseComes from processed wood pulp; also known as dissolving cellulose or dissolving pulp ; used for paper making and other purposes

SteepingThe cellulose sheets are saturated with a solution of caustic soda (or sodium hydroxide) and allowed to steep for enough time for the caustic solution to penetrate the cellulose and convert some of it into “soda cellulose”, the sodium salt of cellulose.

Rayon Manufacturing Process

PressingThe soda cellulose is squeezed mechanically to remove excess caustic soda solution.

ShreddingThe soda cellulose is mechanically shredded to increase surface area and make the cellulose easier to process. This shredded cellulose is often referred to as “white crumb”.

AgingUsed to oxidize cellulose partially and degrade it to lower molecular weights. Degradation should be carefully done to give manageable viscosity in the spinning solution

XanthationThe aged white crumb is placed into a churn, treated with gaseous carbon disulfide. The soda cellulose reacts with the CS2 to form xanthate ester groups The carbon disulfide also reacts with the alkaline medium to form “yellow crumb”. Because accessibility to the CS2 is greatly restricted in the crystalline regions of the soda cellulose, the yellow crumb is essentially a block copolymer of cellulose and cellulose xanthate.DissolvingThe yellow crumb is dissolved in aqueous caustic solution .Because the cellulose xanthate solution has a very high viscosity, it has been termed “viscose”.RipeningThe viscose is allowed to stand for a period of time to “ripen”. Two important process occur during ripening: Redistribution and loss of xanthate groups.FilteringThe viscose is filtered to remove undissolved materials that might disrupt the spinning process or cause defects in the rayon filament.

DegassingBubbles of air entrapped in the viscose must be removed prior to extrusion or they would cause voids, or weak spots, in the fine rayon filaments.Spinning - (Wet Spinning)The viscose is forced through a spinneret, a device resembling a shower head with many small holes.DrawingThe rayon filaments are stretched giving the filaments the properties necessary for use as textile fibers.WashingThe freshly regenerated rayon contains many salts and other water soluble impurities which need to be removedCuttingIf the rayon is to be used as staple (i.e., discreet lengths of fiber), the group of filaments (termed “tow”) is passed through a rotary cutter to provide a fiber which can be processed in much the same way as cotton.

Rayon- Characteristics & Uses

CHARACTERISTICSHighly absorbent ;Soft and comfortable ;Easy to dye ;Drapes well

Thermal properties: Viscose rayon loses strength above 149° C; chars and decomposes at 177 to 204° C. It does not melt or stick at elevated temperatures.

Chemical properties: Hot dilute acids attack rayo.Rayon is attacked by bleaches at very high concentrations. Prolonged exposure to sunlight causes loss of strength because of degradation of cellulose chains.

Abrasion resistance is fair and rayon resists pill formation. Rayon has both poor crease recovery and crease retention.

USESApparel: Accessories, blouses, dresses, jackets, lingerie, linings, millinery, slacks, sportshirts, sportswear, suits, ties, work clothes

Home Furnishings: Bedspreads, blankets, curtains, draperies, sheets, slipcovers, tablecloths, upholstery

Industrial Uses: Industrial products, medical surgical products, nonwovens products, tire cord

Other Uses: Feminine hygiene products

ACRYLIC

Acrylic Fibre- Overview Acrylic Synthetic fibre was often used as a substitute for wool. It was first developed in the mid-1940s but was not produced in large quantities until the 1950s.

Strong and warm, acrylic fibre is often used for sweaters and tracksuits and as linings for boots and gloves, as well as in furnishing fabrics and carpets.

It is manufactured as a filament, then cut into short staple lengths similar to wool hairs, and spun into yarn. Modacrylic is a modified acrylic yarn.

Before 1960, acrylonitrile was commercially produced by adding hydrogen cyanide to acetylene, or by dehydration of ethylene cyanohydrin.

In the Sohio process, propylene, ammonia, and oxygen, react at high temperature in the presence of catalysts such as bismuth phosphomolybdate.

In order to qualify for the description acrylic, the final polymer must contain at least 85% by weight of acrylonitrile units. Acrylonitrile is an addition polymer, the monomers adding or joining end-to-end without liberating any by-product.

Although acrylic polymer is thermoplastic, it does not melt sharply to give a fluid melt suitable for melt spinning, and so must be solvent spun. Acrylic fibres are either wet or dry spun

Acrylic- Manufacturing Process The polymer is formed by free-radical polymerization.

The fiber is produced by dissolving the polymer in a solvent such as N,N-dimethylformamide or aqueous sodium thiocyanate, metering it through a multi-hole spinnerette and coagulating the resultant filaments in an aqueous solution of the same solvent.

Washing, stretching, drying and crimping complete the processing.

Acrylic fibers are produced in a range of deniers, typically from 1 to 15.

End uses include sweaters, hand-knitting yarns, rugs, awnings, boat covers, and beanies; the fiber is also used as a precursor for carbon fiber.

Production of acrylic fibers is centered in the Far East.

Acrylic in action

Properties & Uses of Acrylic Fibre Properties

Acrylic fibers are synthetic fibers made from a polymer(Polyacrylonitrile) with an average molecular weight of ~100,000.

To be called acrylic in the U.S, the polymer must contain at least 85% acrylonitrile monomer.

Typical comonomers are vinyl acetate or methyl acrylate

Acrylic is resistant to moths, oils, and chemicals, and is very resistant to deterioration from sunlight exposure. However, static and pilling can be a problem.

Uses

Acrylic is lightweight, soft, and warm, with a wool-like feel.

It dyes very well and has excellent colorfastness.

It is resilient, retains its shape, and resists shrinkage and wrinkles.

It is quite varied in form and sometimes has an appearance similar to wool or cotton

Acrylic has recently been used in clothing (paschmina) as a cheaper alternative to cashmere, due to the similar feeling of the materials.

The disadvantages of acrylic is that it tends to fuzz (or pill) easily and that it does not insulate the wearer as well as cashmere.

Acrylic Statistics Principal applications in hosiery, sweaters, craft yarn, pile, and knits.

Home furnishings markets represent a smaller percentage of the total market; carpets and rugs, blankets, and upholstery and drapery market sections account for the major volume in this area.

ACETATE & TRIACETATE

Acetate & Triacetate Fibres- Overview Cellulose acetate was invented by two Swiss brothers, Camille and Henri.

In 1905, Camille and Henri developed a commercial process to manufacture cellulose acetate.

In 1924, the first commercial acetate filament was spun in the United States and trademarked as Celanese Acetate yarns were initially developed as an alternative to silk.

Cellulose acetate is one of the earliest synthetic fibers and is based on cotton or tree pulp cellulose

Acetate is a very valuable manufactured fiber that is low in cost and has good draping qualitiesIt is also called the Fiber of beauty beacause it has luster and tactile feeling just like silk fibers.

Acetate Production Process Purified cellulose from wood pulp or cotton linters

Mixed with glacial acetic acid, acetic anhydride, and a catalyst

Aged 20 hours- partial hydrolysis occurs Precipitated as acid-resin flakes Flakes dissolved in acetone Solution is filtered Spinning solution extruded in column of warm

air. Solvent recovered Filaments are stretched and wound onto

beams, cones, or bobbins ready for use

Acetate & Triacetate Fibre Characteristics Acetate Fiber characteristics: Acetate has an unusual combination of

properties that are unmatched by other materials.

Cellulosic and thermoplasticChemical solubilityHydrophilic performance Safe to use High surface area Environmentally soundCan be dyed,

Tri acetate Fibre Characteristics

Shrink resistant Wrinkle resistant Easily washable Generally washable at high temperatures Maintains creases and pleats well

Uses of Acetate & Triacetate Acetate

Apparel: linings, blouses, dresses, wedding and party attire, home furnishings, draperies, upholstery and slip covers. Industrial uses: cigarette filters, ink reservoirs for fiber tip pens. High absorbency products: diapers, surgical products, and other filters. Acetate is found in screwdriver handles, ink pen reservoirs, x-ray films, and a host of other end uses

Triacetate

Particularly effective in clothing where crease or pleat retention is important, such as skirts and dresses.In the 1980s triacetate was also used with polyester to create shiny tracksuits which were very popular at the time. The material was very smooth and shiny on the outside and soft and fleecy on the inside

Acetate in Industry

Celanese Acetate, a business of Celanese, manufactures cellulose acetate products used in filtering and other industrial applications. The name "Celanese" (pronounced: "Sell-un-ease") is derived from a combination of "cellulose acetate" and the phrase "ease of care," referring to the easy wear of the material made from the product.

The original Celanese Corporation was founded by the Swiss Dreyfus brothers, Camille and Henri, who began their research in 1904 in Basel, Switzerland, They opened their first factory in 1910.

Celanese Acetate has manufacturing sites in the US, UK, Belgium, Mexico and China.

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