Relation Between Glass Fibre Orientation and Specific Wear Rate for Duroid

Axis % of fibres oriented Specific wear rate 

Composition 69% PTFE, 15wt. % M0S2, 16wt. % glass fibre 

The effect of speed on wear rate is probably due at least partly to the fact that polymers commonly exhibit visco-elasticity. As a result, increased contact speeds can lead to higher contact stresses. Higher speed also causes higher frictional heating, which will usually result in softening and increased wear. However, the use of polymer composites is best restricted to speeds below one or two metres/second because the combination of frictional heating and poor thermal conductivity leads to overheating and breakdown. 

PTFE is a unique polymer in the formulation of composites, since it may be either the material of the matrix or a friction-reducing filler. It is a very soft polymer, which in the absence of reinforcement will wear rapidly, and it will cold flow under load. As a matrix material it must therefore be effectively reinforced. As a friction-reducing filler it may be used in the form of particles or fibres. Table 12.6 shows the effect of different fillers on the properties of PTFE. Spengler et aP reported an 

Counterface asperities penetrate polymer, wear rate characteristic of initial roughness (microcutting, low cycle fatigue) 

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Table 12.5 Relation Between Glass Fibre Orientation and Specific Wear Rate for Duroid 5813 (Ref.370 ...

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