Polyaramid Polyparaphenylene Terephthalamide ( Kevlar / Twaron )- Properties and Applications - Supplier Data by Goodfellow

Background

Polyaramid Polyparaphenylene Terephthalamide ( Kevlar / Twaron ) is an infusible, wholly aromatic polymer that can strictly be described as nylon T,T - but rarely is. Manufactured only as a fibre (by solution spinning), it has a very high thermal stability and temperature and flame resistance.

In contrast to its chemical isomer Nomex®, the tensile properties of Polyaramid Polyparaphenylene Terephthalamide ( Kevlar / Twaron ) are up to an order of magnitude greater than those of normal textile fibres, because of a high degree of molecular orientation resulting from its stiff linear molecules and their propensity for forming liquid crystals in the spinning solution.

In common with the small number of other highly oriented materials, these Polyaramid Polyparaphenylene Terephthalamide ( Kevlar / Twaron ) fibres have a (small) negative co-efficient of thermal expansion in the axial direction.

Applications

Polyaramid Polyparaphenylene Terephthalamide ( Kevlar / Twaron ) fibres are quite widely used in composites which are lighter than those based on carbon fibre and electrically insulating. Their mechanical properties are generally inferior; more specifically they have a high specific tensile strength approaching that of carbon fibre composites, but quite low strength in compression.

In addition to composites, applications of Polyaramid Polyparaphenylene Terephthalamide ( Kevlar / Twaron ) include protective clothing and body armour, friction products, elastomer reinforcement (e.g. hoses and drive belts), ropes and cords and as high strength high modulus fabrics e.g. high performance sailcloths.

Key Properties

The key properties of Polyaramid Polyparaphenylene Terephthalamide ( Kevlar / Twaron) are tabulated below.

Table 1. Key properties

Chemical Resistance
Acids - concentrated Poor
Acids - dilute Fair
Alcohols Good
Alkalis Good
Aromatic hydrocarbons Good
Greases and Oils Good
Halogens Good
Ketones Good
Mechanical Properties
Tensile modulus ( GPa ) 59 - 124
Tensile strength ( MPa ) 2760
Physical Properties
Density ( g.cm-3 ) 1.44
Resistance to Ultra-violet Fair
Thermal Properties
Coefficient of thermal expansion ( x10-6 K-1 ) -2 along axis
Lower working temperature (°C ) -200
Specific heat ( J.K-1.kg-1 ) 1400
Thermal conductivity ( W.m-1.K-1 ) 0.04 @ 23
Upper working temperature (°C ) 180 - 245
Properties Polyaramid Fibre
Property Value
Material Kevlar 29® Kevlar 49® Kevlar Ht (T129)
Specific Modulus cN/tex 4000 8300 5200
Specific Tenacity cN/tex 190 190 235
Density g.cm-3 1.44 1.45 1.44
Extension to break % 3.7 1.9 3.6
Modulus GPa 58 120 75
Shrinkage @ 100 °C % 0.02
Tenacity GPa 2.76 2.76 3.32

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