Special Use Fibres

Special Use FibersNitin Neha Manish Kushagr Nishu

Nomex

Nomex is an aramid fiber with inherently flame-retardant properties. When exposed to flame, it chars but does not ignite or support combustion. As soon as the flame is removed, the Nomex self-extinguishes. Unlike treated cotton fabrics, the flame retardance will never wash out of Nomex.

Production

▪ The polymer is produced by condensation reaction from the monomers m-phenylenediamine and isophthaloyl chloride.

▪ It is sold in both fiber and sheet forms and is used as a fabric wherever resistance from heat and flame is required. Nomex sheet is actually a calendared paper and made in a similar fashion. Nomex Type 410 paper is the original and one of the larger grade types made, mostly for electrical insulation purposes. Nomex fiber is made in the USA and in Spain (Asturias).

NOMEX Molecular Structure

Physical Properties

Excellent flame resistance and thermal protection Stands up to flame temperatures in excess of 2,000°F Fibers do not melt or drip Resistant to insects and fungi High elongation Cut resistant Abrasion resistant 

Chemical Properties

Outstanding resistance to degradation by radiation

Outstanding resistance to degradation at cryogenic conditions

Resistant to chemicals and industrial solvents Low stiffness of fiber due to chemical bonding

arrangement.

Applications

• Industrial rope and cordage.• Military rope and cordage.• Safety rope.• Firefighter rope.• Extreme environment rope and cord.

Nomex Yarn Nomex Fiber

Nomex Fabric

Novoloid

These are cross-linked, three-dimensional, phenolic aldehyde fibers typically prepared by the acid-catalyzed,

cross-linking of a melt-spun novolac resin with formaldehyde. These fibers are highly flame resistant, but

are not considered to be high temperature fibers. They are used with a wide variety of matrix materials to form

composites. 

Production

A phenolic fiber made by cross-linking a melt-spun novolac resin with formaldehyde. Novoloid fibers have good flame resistance, can serve at temperatures to about 220°C, and are used as reinforcement in a range of thermosetting matrices.

Structure of Kynol Novoloid

Physical Properties

Chemical Properties

• Heat Resistance Inherently flame resistant.

Limited oxygen index (L.O.I.) : between 30 – 34

ExhiFlame bits minimal shrinkage and smoke emission when exposed to flame.

Due to 3-dimensional cross-linked chemical structure, the fibers are thermoset and will not melt .

Can withstand short-term heat exposure in temperatures > 1000C .

When exposed to extremely high air temperature the fibers carbonize and gradually decompose.

• Chemical resistance:

 Strong resistance to acids, alkalis and organic solvents.

Main applications of Kynol products:

▪ Flame resistant safety products:

Fire blankets, flame barriers, drapes, smoke barriers, seat linings, protective curtains and special carpets in :

aircrafts, motorcars, ships, ferries, submarines, hotels, discos, theatres, hospitals, etc.

Cover (fire blocking layer) for mattresses and as filling in sleeping bags for navy, army and civilian use.

Fire extinguishing blankets.

▪ Apparel:

For welders, as linings in gloves, racing car drivers’ and pilots’ jackets, in firemen’s and other rescue coats or suits; escape

hoods for aircrafts and hotel visitors etc.

Thermal insulation, also against radiant heat:

For air condition, ventilation ducts, in shoe soles and for military vehicles,insulation of roofs and walls, also in a blend with rock wool.

Laser, spark and metal splash protection:

Protective curtains, also for welding.

Chemical resistant products:

Gland packings, gaskets, composites, garments, gloves, reinforcement for phenolic resin in walls, flexible tanks; waste water applications

Novoloid fiber and yarn

Novoloid Fabric Aluminised Novoloid

Saran

Material with a greasy, dark green film, first called "Eonite" and then "Saran”.

Saran fiber comes in monofilament, multifilament-twist, and as a staple fiber. It is also available in thermochromic (color changing) and luminescent (glow in the dark) form.

Saran is the trade name for a number of polymers made from vinylidene chloride (especially polyvinylidene chloride or PVDC), along with other monomers.

Ralph Wiley accidentally discovered polyvinylidene chloride in 1933.

Properties remarkable barrier against water, oxygen and aromas superior chemical resistance to alkalies and acids insoluble in oil and organic solvents very low moisture regain; Moisture regain = 0.1-1.0% impervious to moisture, mold, bacteria, and insects soluble in polar solvents. good thermal stability, but above 125°C decomposes to produce HCl good chemical resistance to acids and alkalis do not lose their strength in sunlight do not tend to retain dirt and are easy to clean Heavy fabric high specific gravity Circular ross section Tenacity = 0.7 - 2.4 g/denier (dry or wet) Elongation = 15-30% (dry or wet) Melting point: 160 – 177 Density: 1.1 – 1.7

ApplicationsPACKAGING : Polyvinylidene chloride is applied as a water-based coating to other plastic films such as biaxially-oriented polypropylene (BOPP) and polyethylene terephthalate (PET).

MILITARY : The military sprayed Saran on fighter planes to guard against salty sea spray and carmakers used it for upholstery

HOUSEHOLD : Cleaning cloths, filters, screens, tape, shower curtains, garden furniture.

INDUSTRIAL : Screens, artificial turf, waste-water treatment materials, underground materials.

MISCELLANEOUS: also used for high-quality doll hair that is valued by collectors for its shine and softness.

DisadvantageIt undergoes thermally induced dehydrochlorination at temperatures very near to processing temperatures.

This degradation easily propagates, leaving polyene sequences long enough to absorb visible light, and change the color of the material from colorless to an undesirable transparent brown (unacceptable for one of polyvinylidene chloride chief applications: food packaging).

Therefore, there is a significant amount of product loss in the manufacturing process, which increases production and consumer costs.

Softens at 115 C and loses strength at 99C.

Trademarks(producers)

Saran TC and Saran LS (Asahi-Kasei)

Saran Wrap and Saranex (Dow Chemical)

Ixan and Diofan (SolVin). 

PVCPoly vinyl chloride, commonly abbreviated PVC, is the third-most widely produced polymer, after polyethylene and polypropylene.PVC comes in two basic forms: rigid (sometimes abbreviated as RPVC) and flexible.

Pure poly(vinyl chloride) is a white, brittle solid.  IUPAC name - poly(1-chloroethylene)

Molecular formula - (C2H3Cl)n

ApplicationsThe rigid form of PVC is used in construction for pipe, and in profile applications such as doors and windows. It is also used for bottles and other non-food packaging, and cards (such as bank or membership cards). It can be made softer and more flexible by the addition of plasticizers, the most widely used being phthalates. In this form, it is also used in plumbing, electrical cable insulation, imitation leather, signage, inflatable products and many applications where it replaces rubber.

Additives to finished polymer

There are several flexible PVC applications such as calendered films, extruded profiles, injection moulded soles and footwear, extruded hoses and plastisols where PVC paste is spread on to a backing (flooring, wall covering, artificial leather).

PropertiesIt is insoluble in alcohol, but slightly soluble in tetrahydrofuran.

Elongation at break: 20–40%Notch test: 2–5 kJ/m2

Glass temperature: 82 °CMelting point: 100–260 °CEffective heat of combustion: 17.95 MJ/kgSpecific heat : 0.9 kJ/(kg·K)Water absorption (ASTM): 0.04–0.4Dielectric Breakdown Voltage: 40 MV/m

PVC is a thermoplastic polymer

Spandex

Spandex or elastane is a synthetic fiber known for its exceptional elasticity. It is strong, but less durable than its

major non-synthetic competitor, natural latex. It is a polyurethane-polyurea copolymer that was invented in 1959

by chemists C. L.

▪  

Production

The polymer chain is a segmented block copolymer containing long, randomly coiled, liquid, soft segments that move to a more linear, lower entropy, structure. The hard segments act as “virtual cross-links” that tie all the polymer chains together into an infinite network. This network prevents the polymer chains from slipping past each other and taking on a permanent set or draw. When the stretching force is removed, the linear, low entropy, soft segments move back to the preferred randomly coiled, higher entropy state, causing the fiber to recover to its original shape and length. This segmented block copolymer is formed in a multi-step proprietary process. It is extruded into a fiber as a monofilament thread line or for most products into a multiplicity of fine filaments that are coalesced shortly after they are formed into a single thread line.

Properties

Can be stretched repeatedly and still recover to very near its original length and shape

can be stretched more than 500% without breaking Stronger, more durable and higher retractive force than rubber Lightweight, soft, smooth, supple In garments, provides a combination of comfort and fit, prevents bagging and

sagging Heat-settable — facilitates transforming puckered fabrics into flat fabrics, or flat

fabrics into permanent rounded shapes Dye able Resistant to deterioration by body oils, perspiration, lotions or detergents Abrasion resistant When fabrics containing spandex are sewn, the needle causes little or no damage

from “needle cutting” compared to the older types of elastic materials Available in fiber diameters ranging from 10 denier to 2500 denier Available in clear and opaque lusters

Uses

Garments where comfort and fit are desired: hosiery, swimsuits, aerobic/exercise wear, ski pants, golf jackets, disposable diaper, waist bands, bra straps and bra side panels

Compression garments: surgical hose, support hose, bicycle pants, foundation garments

Shaped garments: bra cups

Fiber Care Tips

Hand or machine wash in lukewarm water Do not use chlorine bleach on any fabric containing spandex. Use

oxygen or sodium perborate type bleach Rise thoroughly Drip dry. If machine dried, use low temperature Ironing, if required, should be done rapidly. Do not leave the iron

too long in one position. Use low temperatures setting. 

Kevlar

▪ a synthetic fiber of high tensile strength used especially as a reinforcing agent in the

manufacture of tyres and other rubber products. 

Properties

five times stronger than steel, yet it is extremely lightweight. 

does not rust or corrode

absorbs vibrations readily. 

breaks down when exposed to the ultraviolet rays in sunlight.

  Dry-cleaning agents bleach, and repeated washing can affect Kevlar negatively

Kevlar is made in three common grades: Kevlar, Kevlar 29, and Kevlar 49. 

Kevlar Molecular Structure

Bold represents a monomer unit, dashed lines indicate hydrogen bonds.  

Applications

▪ Kevlar is typically used in tires. 

▪ Kevlar 29 is used in body armour, industrial cable and brake linings

▪ Kevlar 49 is used in applications such as plastic reinforcement for boat hulls, airplanes, and bicycles.

Kevlar Fabric Kevlar Yarn Kevlar Fiber

Bibliography

▪ P. Hedenberg and P. Gatenholm – Applied polymer science

▪ V. Favier , H. Chanzy and J.Y. Cavaille – Macromolecules and Polymers

▪ J. Johnson – What is Kenaf