Carbon and graphite

Carbon fibres, including graphite fibres have excellent properties including high stiffness and tensile strength and they are relatively inert to environmental conditions.

They have replaced asbestos in textiles that are submitted to vibration at high temperature. They have been used in demanding applications for gaskets, packing and diaphragms. They are also used as fibrous reinforcements for polymeric bushings.

Carbon fibres are too costly for building materials. They are comparatively brittle and cannot be submitted to high shear mixing. They are not incombustible and they conduct electricity. Airborne carbon fibres can cause short circuits in electrical controls and electronic apparatus.

Carbon fibres have a fibrilar structure similar to that of asbestos and their surface properties can be modified by suitable treatments. Thus is sometimes essential for controlling the interfacial properties of composites, The carbon fibres are inert to most Chemicals but show anisotropy in physical properties such as thermal expansion.

Costs for car’oon fibres have been reported in the range of twice to one hundred times as much as the cost. Of chrysotile asbestos. Exotic graphite fibres cost as much as 24,000 times the cost of asbestos. Prices ranging between 16 and 66 US S/kg are common.

The following properties have been reported for carbon fibres:

Diameter 8 or 9 micrometers
Specifie gravity 1.76 to 1.9
Tensile strength 1600 to 3100 MPa
Tensile modulus 200 to 700 GPa
Temperature limits 1427 to 35000C

Compared against chrysotile asbestos, carbon fibres are adequate with regard to reinforcing strength; heat resistance and chemical resistance; but inferior with regard to cost and availability.

Substitutes for asbestos – Marcel Cossette