Aramid (Kevlar) fibre

Ararnid fibres, better known by their trade name Kevlar, are aromatic polyimides and are produced either in monofilament or in pulp form.

They have a high tensile strength and stiffness, and are good electrical insulators. They begin to loose strength around 3000C and their rate of creep under load increases as the temperature rises. Sheet gasketing containing aramid fibres is notoriously difficult to cut and punch, and cannot be die formed. Aramid fibres are also difficult to mix and homogeneous mixtures are difficult to obtain. Aramid monofilaments are not easy to weave but they have produced a range of useful textiles.

Aramid fibres are too costly for use in building materials but they have been substituted for asbestos in several demanding product applications. Aramid fibres have a low thermal mass and thus cannot be used into insulate safes that require exposure to fire for several hours. Likewise, aramid gloves can replace asbestos gloves in many types of service but they cannot be worn by workers who manipulate red – hot steel wires to thread them through drawing dies. For such applications only chrysotile asbestos gloves will do.

The costs of aramid fibres have been reported as ranging between 50 and 600 times the cost of the asbestos they replace. The range of prices is 10 to 100 US $/kg.

The following properties are assigned to aramid fibres:

Tensile strength 2600-3700 MPa
Young’s modulus 62-160 GPa
Diameter 10-12 micrometers
Density 1,45g/cm3
Temperature limits 204-2600C

Compared against Chrysotile asbestos, aramid fibres are adequate concerning their reinforcing strength and they may have adequate heat resistance and chemical resistance. They are inferior with regard to cost and availability.

Substitutes for asbestos – Marcel Cossette