Textilelearner.blogspot.ca-an Over View of High Performance Fibers

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An Over View of High Performance Fibers

Introduction:

High-perf ormance f iber-reinfo rced cementitious composites (HPFRCCs) are a group of f iber-reinf orced

cement-based composites which possess t he unique ability to f lex and self- st rengthen before f racturing.

High-perf ormance f ibers, used in fabric applications ranging fro m bulletproof vests to trampolines, must have

a suf f icient number of chemical and physical bonds f or t ransf erring the st ress along the f iber.To limit their

deformation, the f ibers should possess high stif f ness and strength. Stif f ness is brought about by the degree

to which the chemical bonds are aligned along the f iber axis. In f iber-reinfo rced compos ites, the f ibers are the

load-bearing element in the s tructure, and they must adhere well to the matrix material.

In a sense, all f ibers except the cheapest commodity f ibers are high-perf ormance f ibers. High-perf ormance

f ibres of f er special propert ies due to the demands of the respective application. These demands cover

propert ies such as high tension, high elongation and high resistance to heat and f ire and other environmental

attacks. They are generally niche products , but some are produced in large quantities. The natural f ibres

(cotton, wool, silk . . .) have a high aesthet ic appeal in fashion f abrics (clothing, upholstery, carpets): Until 100years ago, they were also the f ibres used in engineering applications what are called technical or industrial

text iles.With the introduction of manufactured f ibers (rayon, acetate, nylon, polyester . . .) in the f irst half of

the twentieth century, not only were new high-perf ormance qualities available f or f ashion f abrics, but they als

of f ered superior technical properties. For example, the reinforcement in automobile tyres moved f rom cot to n

cords in 1900, to a sequence of improved rayons f rom 1935 to 1955, and then to nylon, polyester and steel,

which dominate the market now. A similar replacement of natural and regenerated f ibres by synthetic f ibres

occurred in mos t technical textiles.

The maximum strengths of commercial nylon and polyester f ibres approach 10 g/den (~1 N/tex) or 1GPa*, with

break extensions of more than 10%. The combination of moderately high st rength and moderately high

extension gives a very high energy to break, orwork of rupture. Good recovery properties mean that they canstand repeated high-energy shocks.

In this respect, nylon and polyester f ibers are unchallenged as high perf ormance f ibers, though their increase

in stif f ness with rate of loading reduces their performance in ballistic applications. It is notable that po lyester

has proved to be the f ibre of choice for high-perf ormance ropes with typical break loads of 1500 tonnes, use

to moor oil-rigs in depths of 10002000m. The high-stretch characteristics of elastomeric fibres, such as

Lycra, have an undeveloped potential f or specialised technical applica-t ions. However, because o f their large-

scale use in general textiles, these f ibres are dealt with in another book in this series.

List of High Perf ormance Fiber:

1. Glass Fiber

2. Carbon Fiber

3. Aramid f iber

4. PBI (polybenzimidazo le) Fiber etc.

5. PBO (polyphenylenebenzobisoxazo le) and PI (polyimide) Fiber

6. PPS (polyphenylene sulf ide) Fiber

7. Melamine Fiber
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Glass f iber

Carbon f ibers

8. Fluoropo lymer (PTFE, Polytetraf luoroethylene)

9. HDPE (high-density polyethylene)

10. Ceramic f ibers

11. Chemically resistant f ibres

12. Thermally resistant f ibres

Glass Fiber:

Glass fiberis the o ldest, and most f amiliar, high-perf ormance f ibre. Fibres have been manufactured f romglass s ince the 1930s. Although early versions had high-st rength, they were relatively inf lexible and not suitab

f or several text ile applications. Today's glass f ibres of f er a much wider range of propert ies and can be found

in many end uses, such as insulation batting, f ire-resistant f abrics, and reinforcing materials for plast ic

composites. Items such as bathtub enclosures and boats, of ten ref erred to as `f ibreglass' are, in reality,

plastics (often crosslinked polyesters) with glass fibre reinforcement. And, of course, continuous filaments of

opt ical quality glass have revolutionized the communications indust ry in recent years. Carbon Fiber:

Carbon fiber, alternatively graphite f iber, carbon

graphite o r CF, is a material cons isting of f ibers about

510 m in diameter and composed mostly of carbon

atomsCarbon f ibre may also be engineered f orst rength. Carbon f ibre variants dif f er in f lexibility,

electrical conduct ivity, thermal and chemical

resistance. Altering the product ion method allows

carbon f ibre to be made with the st iff ness and high

st rength needed for reinf orcement of plastic

composites, o r the sof tness and f lexibility necessary

f or conversion into textile materials. The primary

f actors governing the physical properties are degree

of carbonization (carbon content, usually greater

than 92% by weight) and orientation o f the layered

carbon planes. Fibres are produced commercially witha wide range of crystalline and amorphous content.

Because carbon cannot readily be shaped into f ibre form, commercial

carbon f ibres are made by extrusion o f some precursor material into

f ilaments, f ollowed by a carbonization process to convert t he f ilaments

into carbon.

Aramid Fiber:

Aramid fiberare among the best known of the high-performance,

synthet ic, organic fibres. Closely related t o polyamides, aramids are

derived f rom aromatic acids and amines. Because of the stability of the

aromatic rings and the added st rength of the amide linkages, owing to

conjugation with t he aromatic st ructures, aramids exhibit higher tensile

st rength and t hermal resistance than aliphatic polyamide. The para-

aramids, based on terephthalic acid and p-phenylene diamine, or p-

aminobenzoic acid, exhibit higher st rength and thermal resistance than those with the linkages in meta

pos itions on the benzene rings. The greater degree of conjugation and more linear geometry of the para

linkages, combined with the greater chain o rientation derived f rom this linearity, are primarily responsible for

the increased st rength. The high impact resistance of the para-aramids makes them popular for `bullet- proo f

body armour. For many less demanding applications, aramids may be blended with o ther f ibres.

PBI Pol benzimidazole :
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PBI (polybenzimidazole) is another f ibre that takes advantage of the high stability of conjugated aromatic

st ructures to produce high thermal resistance. The ladder-like structure of the polymer further increases the

thermal stability. PBI is noted f or its high cos t, due bo th t o high raw material cos ts and a demanding

manufacturing process . The high degree of conjugation in the polymer structure imparts an orange colour tha

cannot be removed by bleaching. When converted into f abric, it yields a sof t hand with go od moisture regain.

PBI may be blended with aramid or other f ibres to reduce cost and increase f abric st rength.

PBO (polyphenylenebenzobisoxazo le) and PI (polyimide) are two other high- temperature resistant f ibres

based on repeating aromatic structures. Both are recent additions to the market. PBO exhibits very goodtensile strength and high modulus, which are usef ul in reinf orcing applications. Polyimide's temperature

resistance and irregular cross-section make it a good candidate f or hot gas f iltrat ion applications.

PPS (polyphenylene sulf ide) exhibits moderate thermal stability but excellent chemical and f ire resistance. It is

used in a variety of f iltrat ion and other industrial applications.

Melamine Fiber:

Melamine f iber is primarily known f or its inherent thermal resistance and outstanding heat-blocking capability i

direct f lame applications. This high stability is due to the crosslinked nature of the polymer and the low therma

conductivity of melamine resin. In comparison with o ther high-perf ormance fibers, melamine f ibres o f f er

excellent value for products designed fo r direct f lame contact and elevated temperature exposures. Moreovethe dielectric properties, cross-section shape and distribution make it ideal f or high- temperature f iltrat ion

applications. It is sometimes blended with aramid or other high-perf ormance f ibres to increase f inal f abric

strength.

Fluoropolymer (PTFE, polytetraf luoroethylene) of f ers extremely high chemical resistance, coupled with good

thermal stability. It also has an extremely low coef f icient o f f riction, which can be either an advantage or

disadvantage, depending on the use.

HDPE (high-density polyethylene) can be extruded using special technology to produce very high molecular

orientat ion. The resulting f ibre combines high st rength, high chemical resistance and goo d wear properties wi

light weight, making it highly desirable f or applications ranging from cut-proof protective gear to marine ropesSince it is lighter than water, ropes made of HDPE f loat. Its primary drawback is its low so f tening and melting

temperature.

Ceramic Fiber:

Ceramic is a high perf ormance f iber. The need f or reinf orcements f or st ructural ceramic matrix composites

(CMC) to be used in air at t emperatures above 1000C, as well as f or t he reinf orcement f or metals (MMCs),

has encouraged great changes in small-diameter ceramic f ibres since their initial development as ref ractory

insulation. Applications envisaged are in gas turbines, both aeronautical and ground-based, heat exchangers,

f irst containment walls f or f usion reactors, as well as uses f or which no matrix is necessary such as candle

f ilters f or high temperature gas f iltrat ion. Ceramic f ibres can withstand such demanding conditions but also ar

of ten required to resist static or dynamic mechanical loading at high temperature, which can only be achievedby a close control o f their microst ructures.

Ideally, ceramic f ibres s hould show suf f icient f lexibility so that preforms can be made by weaving and

subsequent ly inf iltrated by the matrix material. This can be achieved with ceramics, which have high Youngs

moduli, if the f ibres have suf f iciently small diameters, because f lexibility is related to the reciprocal of the

f ourth power of the diameter.

Alumina and silicon carbide bulk ceramics are widely used f or their high stif f ness and good high t emperature

mechanical properties in air; however, they are generally weak due to the presence of critically sized def ects.


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Chemically Resistant Fibers:

Chemically resistant o rganic polymeric f ibres include those which are designed to resist chemical attack for

acceptable periods during their service lives at both ambient and elevated temperatures. As a consequence of

their generally inert structures they may also be f lame resistant and so address markets where that property

also desirable.

Fluorinated f ibres: PTFE, PVF, PVDF and FEP (ARH) and Chlorinated f ibres: PVDC (ARH) are Chemically

resistant fibers.

Thermally Resistant Fibers:

Thermally resistant organic polymeric f ibres include those that resist thermal degradation and some degree o

chemical attack, notably oxidation, f or acceptable periods during their service lives. As a consequence of their

generally inert s tructures, like the chemically resistant f ibres in the previous chapter, they may also be f lame

resistant and so address markets where that property is also desirable. Their thermal resistance derives f rom

their possessing aromatic and/or ladder-like chain st ructures that o f f er a combination of both physical and

chemical resistance and the f ormer is quantif ied in terms of high second order temperatures, pref erably abov

200 C or so , and very high (>350 C) or absence of melting transitions .

Thermosets (HE and HS), Melaminef ormaldehyde f ibres, Basof il (BASF) (HE) are Thermally resistant f ibres.

Conclusion:

An ideal reinf orcing f iber must have high tensile and compress ive moduli, high tensile and compressive

st rength, high damage to lerance, low specif ic weight, good adhesion to t he matrix materials, and good

temperature resistance. Their are huge application o f high perf ormance f iber. Proposed uses f or HPFRCCs

include bridge decks, concrete pipes, roads, st ructures subjected to seismic and non-seismic loads, and othe

applications where a lightweight, strong and durable building material is desired.

References:

1. High-perf ormance f ibres Edited by J W S Hearle

2. http://en.wikipedia.org

3. htt p://stuf f .mit.edu/af s/athena.mit.edu/course/3/3.064/www/slides/Advanced_Fibers_MRS.pdf

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