The strategies of the world are changing direction as a result of the innovative developments and technological evolutions. This change in the scenario has put lot of thrust on R & D activities to deliver High Performance products to various applications. Proper utilization of the latest technology and using a techno engineering approach is the need of the hour to bring a sea change in the departments where they are to be modernized.

A road map has been created identifying the critical areas with a view to equip the undeveloped areas with the start of the art performance with dual object of awakening the industry to modern trends and thereby meeting the expectations of the particular field. High performance textiles are the one, which is to fulfil the modern requirements of any industry.

High performance fibres and their high tech products possess a wide range of properties like high modulus; high strength and low density and they are also capable of withstanding high temperatures. This makes them useful for Aerospace, Nuclear Biological Chemical warfare protective clothing, Ballistic armor applications (Bullet proofs, Helmets).

HIGH PERFORMANCE TEXTILES

INTRODUCTION

Many high performance fibres have consolidated the market positions in various application areas. The textile fibres that are used for producing high performance products are increasing day by day. These fibres and composites made from them gained rapid acceptance in a broad range of technologies. This is because of their mechanical properties, outstanding abrasion resistance, fatigue, chemical resistance and cut resistance; and all above, it is their inherent damage tolerance.

There are various polymers finding their place in high tech applications like spacecrafts, composites, etc. In such places weight reduction is one of the main important thing. Development of lightweight, high modulus textile structures makes use in wide area. Use of high performance insulating materials such as Thinsulate, hollow fibres,etc.,makes it apply for thermal resistant places. Various fibres like High performance Polyethylene, Aramide, Glass fibres, Polyether ketone, Arimide and other polymers can be used for applications like resistance to chemicals, thermalshielding, EMIshielding.tyres, composites, aerospace, ballistic protection, sports equipments, etc.

Altering some chemical structures are discussed in the article produces polymers with high tenacity and high modulus, low density.

Strength and Stiffness

Pre industrial fibres, such as cotton, wool and silk, typically had tenacities in the range of 0.1 0.4N/tex and initial modulo from 20 to 5N/tex, though fibres such as flax and ramie could go higher in strength and stiffness. A part from silk, which was the fibre used in some demanding applications such as parachute fabric, they were all short fibres, so that the conversion efficiency to yarn and fabric strength was low. The earlist regenerated cellulose fibres, such as viscose rayon and acetate, had strengths in cellulose fibres. Continuous filament rayon yarns such as Tenasco, with strength of 0.4N/tex, and was introduced for use in tyre cords.

CONCLUSION

High performance fibres can be used for innovative diversified high tech applications because of its high strength and temperature stability. They replace traditional use of metals in places where the weight is to be reduced. There are other areas that will evolve because of the ever-growing stringent requirements of energy saving in transportation (plane). This fibre has the potential to participate in the solutions of high tech products of today and tomorrow.

REFERENCE

1. Tatsuya H. and Philips G.O., New. Fibres, Wood head Publishing Limited (UK), 1997 (Second Edition), pp. 12, 46, 117, 12}, 131, 152,165,184,193.

2. Kawata T., Kanebo Gohesen Ltd, Chemical Fibres International, 48 (2), 1998, pp. 81-82.

3. Ravi Kumar M.N.V. and Dutta P K. Synthetic Fibres, 27 (I), 1998,

4. John P 0' Brien and Anzeja A. P., Review of Progress In Coloration,Vol. 29, ] 999, p. 1.

5. Aneja A.P., Textile Asia, Oct. 1998, pp 36-38.

6. Rocha 1. Textile Month, March 1998, p. 32.

7. www.fibrelink.com

8. www.undyarns.co.uk


About the author:

D.Gopalakrishnan & R.K.Aswini are in the Department of textile technology, PSG College of technology, Coimbatore 641 004 Email : dgk_psgtech@yahoo.co.in and achu_stars@yahoo.co.in

To read more articles on Textile, Fashion, Apparel, Technology, Retail and General please visit www.fibre2fashion.com/industry-article

Covers for the break and acceleration booster: these parts are manufactured and cured according to a special process in order to withstand the extreme space requirements. Critical for these parts are low weight, high strength and high quality.

The following important technical advantages can be obtained in comparison with GRANULAR ACTIVATED CARBON and other fibres:

Highly efficient and cost-effective removal of very small amounts of impurities from large amounts of air or liquids;

High fibre surface-to-volume ratio and direct connection of micropores to the fibre surface significantly shorten diffusion distance and increase speed of adsorption and desorption;

Pore dimensions and surface characteristics can be tailored to the application;

Depending on the target material, excellent rates of removal may be obtained even at ppb concentration level;

Fibres can be locked into textile structures, preventing channeling and minimizing loss and contamination due to antiparticles abrasion;

Textile structures are often convenient for filter design and assembly, and compared to textiles impregnated with powdered carbon there is less shedding of particulars and no pore block-age by binders;

Shed particles tend to be fibre fragments with a minimum of 10um dimensions, easily trapped in particulate filter media;

The strength of all activated kynol products is superior to similar viscose products, especially when wet;

POLY (ETHERETHERKETONES): PEEK (BM)

POLYETHERKETONES

PEEK (Polyetheretherketones) is the foremost member of a family of semi-crystalline aromatic thermoplastic polymers, the polyetherketones (PEKs). It is capable of being formed into an extensive range of monofilaments and fibres using high-temperature melt-spinning techniques.

PEEK fiber-performance factors:
Temperature performance: A continuous operating temperature for many applications of up to 260oC, with short excursions to 300oC being possible, and a non-brittle low temperature performance down to - 60oC.

Chemical inertness: It is unaffected by high-temperature steam and most fluids and chemical reagents. However, it is dissolved by concentrated sulphuric acid (>50%) and degraded by strong oxidizing agents such as nitric acid.

Abrasion resistance: It has a tough, low friction, low wear, cut-resistant surface and is particularly good at residing abrasion at elevated temperatures and relatively high surface speeds.

Dimensional stability: It exhibits low creep and low shrinkage, especially below its T3 (143oC). It has excellent dynamic recovery and flexes fatigue performance.

Polymer purity: Fibres are exceptionally pure, without the need for stabilizing additives, and they have EEC and FDA approval for medical and food-contact use.16,17 A good low surface energy self-cleaning characteristic minimize contamination in use.

Flammability: Fibres are self-extinguishing with an LOI of 35 % while emitting one of the lowest levels of smoke and toxic gases.

Processability: The room temperature physical properties of PEEK fibres are similar to those of both polyester and nylon, so textile processes such as weaving and braiding can be conveniently performed.

Sustainability: Recovery and recycling of PEEK as a material can be carried out under certain conditions with little loss of key physical properties.


The most notable was Fortson, which was made by highly stretching acetate yarns and then converting them to cellulose. This gave a tenacity of 0.6 N/tex and a modulus of 16 N/tex. Building on the experience of the aramide fibres, a new cellulose fibre, Bo cell, has been produced in Akzo-Nobel laboratories by spinning from liquid crystal solution in phosphoric acid. The polymer cost would be much less that for aramids and similar high performance fibres, though the spinning costs would probably be similar.

Meanwhile, nylon had come on the market in 1938 and found wartime technical uses. Tenacity was about 05N/tex. Textile grades of the polyester fibre polyethylene terephthalate, which followed, had a similar tenacity but a higher modulus of about 10 N/tex. Development for industrial uses, such as tyre cords and ropes, has taken nylon and polyester to tenacities over 0.8 N/tex and modulus of 9 N/tex for nylon.

Protective clothing with a focus on fire protection

ARAMID POLYMERS.

Particularly Meta aramids, exhibit high temperatures resistance and stability. This gave a strong incentive to develop these materials for specific industrial heat resistant applications. Poly m-phenyleneisophthalamide. (Nomex) was the first aramid fibre developed with good thermal stability are exposure temperatures as high as 5000C and long term stability in environmental temperatures as high as 2200C.

When Meta aramid fabrics are rapidly heated in a flash fabrics are rapidly heated in a flash fire, the vaporized moisture and degradation gases expand the softened polymer. This expanded material forms carbonaceous insulating foam up to ten times the thickness of the original layer. When the seemed ideal for use in clothing, which can benefit form this intumescences.

Hand injuries count, and heavily in the safety statistics. Metal sheet forming, glass manufacturing and handling, and food processing are but a few areas where hand protection is a standard. Formerly made of cotton, synthetic commodity fibres, metal and other basic materials, gloves are now more and more manufactured form armids, mostly para aramid, either lone or in blends. The advantages are several, including the cut and puncture resistance through adequate coating, the abrasion resistance, the inherent thermal and insulating properties against heat and cold, and the tremendous weight saving which is part of better comfort properties.

Advanced Composites

Advanced composites reinforced with aramid fibres have found significant applications in areas where the strength to weight and stiffness to weight ratio of these composites makes them more attractive for use than conventional materials such as aluminum and steel. This has been particularly evident where systems engineering has been used to incorporate fibres with high properties into structural components aircraft.



Carbon fibers are not perfectly suitable since they are unyielding and undergo brittle fracture, despite their stiffness and compressive strength. This brittle behavior is attributed to their rigid coplanar ring structure.

The usually expected significant reduction in composite compressive strength with the increase of the modulus has not been observed in para aramid fibres. Such fibres in a resin mix have structural features that provide excellent damage tolerance. Under compressive strain (0.5%) para aramid molecules tend to buckle rather that fracture.. This is in part due to the molecular rotation of the amide carbon to nitrogen, a bond, which allows configurationally changes without resulting in bond cleavage.


Twaron and Technora protective gloves for ropes and cables

Bullet proof vest

Other important applications and future directions

There are several ends use technologies where aramids provided significant benefits. After minor modifications, the well accepted classification described in the recent literature. Notice that each specific advantageous property can be almost seamlessly related to the polymer or the fibre attributes.

There are ends use market segments that have been rethought because of the aramids, such as the replacements of asbestos by para aramid pulps. There are other areas that will continue to evolve because of the over growing stringent requirements for energy saving in transportation for example. The aramid contribution in this sector is out standing. Clearly communications, including transportation as well as transmission, leisure and sports, life protection, and health and safety in general, have been tremendously improved and adapted to modern technologies in part because of the aramids.

Thermotropic liquid crystal polymers (TLCP)

Research into liquid crystal polymers dates back to the 1970s. This research has resulted in a commercially available melt spun wholly aromatic polyester fibre called Vectran. This high performance fiber is used in numerous applications around the world that require its unique properties. Because of its relatively high cost, it remains a niche market product driven by cost performance benefits. Nevertheless, it significantly improves end product performance when used properly. Much has been written about liquid crystal polymers (LCP).

Liquid quasi-crystal: (a) the molecule, (b) the supramolecular dendrimer, (c) the proposed quasi-periodic arrangement of the spherical dendrimers, (d) X-ray diffraction pattern showing 12-fol


Vectra and Vectran

The commercially available TLCP fibre, Veteran, is produced from Vectra LCP polymer. This Polymer is made by the acetylation polymerisation of p- hydroxybenzoic acid and 6-hydroxy-2 naphthoic. It is one of a family of naphthalene based thermo tropic liquid crystal! Polymers developed by Cleanness Corporation in the 1970s. No classical glass transition temperature is clearly observed in the polymer, although molecular transitions do occur with increasing temperatures. Research and development for the polymers and fibres were focused on tyre cord, to compete with para aramids. When a cost advantages with these TLCP polymers could not be realized in tyre cord, emphasis shifted towards resin development for electronics parts.

The excellent dielectric properties resulted of the polymer and tight tolerances allowed during injections molding resulted in commercial success with the polymer and the start up of the first commercial liquid crystal polymer manufacturing plant in 1989.High strength 23 28g / denier tenacity (2 2.5N/ tex), is achieved in TLCP fibres by heat-treating in an inert atmosphere. Again, some type of lubricant, normally water, is initially applied to ease processing. However, care must be taken to remove the water before the final heat treatment temperatures are reached, to preserve the inert atmosphere required and thus achieve maximum physical properties. The fibre is required and thus achieves maximum physical properties. The fibre is produced as a continuous filament. Typical properties are given in Table. There are no significant environmental issues in the production of TLCP fibres.

TLCP fibres have been produced from polymers with varying chemical compositions to achieve in initial modules in the range of 850 1000g/ denier (80 90 n/ tex; 105 124 Gpa) However, these fibres were not commercialized because of their lower tensile strength and flex fatigue when compared with commercial TLCP fibre products. In the last quarter of the twentieth century, a second generation of manufactured fibres became available. As shown in Fig. 1.1 these high performance fibres showed a step change in strength and stiffness. They are high modulus, high tenacity (HM HT) fibres. This is the characteristic feature of the polymeric and inorganic fibres.

HIGH PERFORMANCE POLYETHYLENE

Cut and puncture resistance

The protecting properties of HPPE fibres can be exploited not only ballistic application, but also in protection against in, for example cut resistant gloves, fencing suits and chain- saw hoses. In cut resistance the best protection is achieved when high performance fibres are combines with stainless steel or glass fibres.

In engineered yarns, HPPE filament or staple fibre and various other yarns such as stainless steel glass, polyamide, polyester and cotton are combined, partly to improve the cut resistance, partly to improve for example wearing comfort.



Puncture resistance depends on both the fibre properties and the resistance of the fabric construction against penetration between the yarns. A normal knitted HPPE fabric can easily stand the test for fencing suits against penetration by the blunted weapon, but an ice pick will easily penetrate such a fabric. The low moisture sensitivity and good chemical resistance of HPPE fibres guarantee high durability in the wash and wear cycles of protective clothing.

Low speed impact

In composites, HPPE fibres can absorb the impart energy that would otherwise destroy the brittle reinforcing glass or carbon fibres. I addition, the use of HPPE affords great weight savings. In motor helmets, for instance, a weight saving of 300 400 g has been realized down to 40% of the original shell weight. Even in combinations with wood laminates for boat hulls for instance, HPPE fibres can strongly improve impact resistance.

Netting

Normally fishing nets, safety nets, etc., are made by knotting braided HPPE twines to form net panels that are used to build, for example, a trawl net. Single knots in HPPE nets may lead to knot slippage owing to the slippery nature of the fibres so double knots are advised. In knotless nets (Rachel and Nichimo) the panels are produced directly from the yarn and twines are not made first. Heat setting is common practice with HPPE nets for the same reasons as with ropes but also to improve fixation of the knots.

Fishing Nets

Nonwovens: This construction is used in ballistic protection against bullets (police vests, light weight Armour panels) as this gives a far better protection at the same weight than fabrics. Dynamic fraglight is a needle felt non woven, produced from staple fibre, that is used, for example in military vest, for the protection against fragments from exploding grenades and bombs.
Composites and laminates

In non ballistic composites, HPPE fibres are mainly used to improve the impact resistance and the energy absorption of glass or carbon fibre reinforced products. Woven fabrics or hybrid with glass or carbon can be used and the fibre or the fabric can be carbon or plasma treated to improve the adhesion of the matrix to the fibre. The matrix is normally an epoxy or a polyester resin. The only basic limitation here is that the curing temperature should not exceed 1400C.In composites used for ballistic protection, such as helmets and light- weight Armour panels, only the ballistic fibre types are used. Both fabrics and the unidirectional products are used with thermoses and thermoplastic matrix systems. The fibre content is normally far higher than with no ballistic composites.
Ballistic protection.



HPPE fibres have a high-energy absorption at break and, owing to the low weight; the specific energy absorption is also very high. This opens up opportunities for these fibres in applications that need a combination of low weight and protection against mechanical threats.

Most important in ballistic protection are the mechanisms of energy absorption at ballistic speeds. The tenacity and elongation of break determine the amount of energy that can be absorbed by an amount of fibres. The specific modules determine the sonic velocity in the fibre and that indicates the area of the fabric that is involved in stopping the projectile. the specific energy absorption and the sonic velocity of fibres; the primary factors that determine the weight needed to stop a projectile.

Ropes

The low weight and high strength of HPPE fibres make it possible to produce heavy duty ropes with very special characteristics. HPPE ropes float on water, are flexible and have a low elongation. Thus, they are very easy to handle. Abrasion resistance and fatigue are good to any standard, which is why HPPE ropes last much longer than other rope.

HEAT TREATED OXIDISED ACRYLICS:

Further heat treatment of oxidized acrylics fibres in an inert atmosphere promotes a further improvement in heat and flame resistance. One product, produced under license from this technology, is Curlon (Orcon Corporation) whose properties have been reviewed recently. The fibres have a crimp, hence the name, are circular and are available in diameters of 8 and 11um. While the tensile strength (0.5Gpa) and extensibility (4.5%) are closer to those values more typical of carbon fibres, and the specific gravity of 1.54 reflects this as well, the Limiting Oxygen Index has increased to 56 %. Because of its increased degree of carbonization, toxic gas emissions, particularly those of HCN, when heated to temperatures up to 1000oC, are claimed to be less than for normal oxidized acrylics. The higher density improves the acoustic insulating qualities and so this fibre is finding application in thermal-acoustic, fire-blocking, nonwoven fabrics in aircraft and marine environments.

POLYBENZIMIDAZOLE (PBI):

PBI fibre is a high-performance fibre recognized for its exceptional thermal stability and chemical resistance. These two qualities, along with its excellent textile processing characteristics, have secured PBI fibre a unique position in the high-performance fibre markets. Since around 1990, PBI fibre has found acceptance and is known as the premium product for many performance-based applications. These include fire protective fabrics for personnel, friction products, and fire-blocking substrates for aircraft. While PBI fibre is relatively new to the civilian market place, it was then that the US Air Force Materials Laboratory (AFML) contracted with the former Celanese Corporation to develop the polymerization and spinning processes for a high-temperature resistant fibre. Later, after the 1967 fire in the Apollo spacecraft, AFML and NASA examined PBI fibre as a non-flammable material for flight suits that would afford maximum protection to astronauts or pilots in oxygen-rich environments. After years of pilot scale manufacturing and use in highly specialized military and aerospace applications.

FIBRE PROPERTIES AND APPLICATIONS:

Flame and thermal stability: PBI fibre will not undergo sustained burning in air, as demonstrated in the limited oxygen index test. The lowest concentration of oxygen that will sustain burning is 41 %. Another standard test used to evaluate fire or flame resistance is the vertical flammability test (FSTM 191-5903). In this test, a fabric sample is exposed to a high flame temperature for a set time. Flammability performance is determined by measuring the after-flame time on the fabric and the length of fabric destroyed by the flame (char length). Fabric produced from PBI fibre exhibits no after-flame and minimal char length (10mm or 0.4 inches), further confirming PBIs exceptional flame resistance.

PBI fibre maintains its physical and mechanical integrity during and after exposure to a wide range of severe temperatures, and thermal stability has been examined in numerous high-temperature exposure tests.


The main ARIMID fibre applications exploit the high temperature and flame-resistant properties and are summarized as follows:

Protective clothing: Outerwear, underwear and gloves may be made from 100 % P84 or blended with lower cost fibres such as flame retardant viscose (e.g. a 50/50 P84/Viscose FR (Lenzing) blend is used for knitted underwear with high moisture absorbency) or with high tenacity polyaramids to increase wear and tensile characteristics. Spun-dyeing of P84 fibres enables their natural colour to be replaced by those demanded by customers who may, for instance, require more appropriate bright safety colours. The protective character of these aramid-containing fabrics is not only their tendency not to decompose at high temperatures but also to provide high levels of thermal insulation, which may be improved by increasing fibre crimp levels.

Fire blanket

Braided packing: P84 fibres are ideal candidates for high-temperature seals and packing, which may be impregnated with lubricants and PTFE dispersions when requiring higher levels of chemical resistance.

High temperature filtration: Hot gas filter bags may be used up to 260o C for prolonged periods; experience has shown that continuous use for periods of years is possible at temperatures as high as 160o C with peaks up to 180o C being permissible.

Aircraft and other transport interiors: Three-dimensional components with structural rigidity may be fabricated from nonwoven fabrics following heating above the second order transition temperature, which causes fibre contraction and consolidation of the structure with some fibre-to-fibre adhesion occurring. These low densities, rigid and fire-resistant structures can replace conventional materials where low weight is at a premium, such as in aircraft and high-speed trains.

Space Exterior Covers for Boosters