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Polymer Lubrication: The low thermal
conductivity of polymers inhibits heat dissipation, which
causes premature failure due to melting. This condition is
exacerbated if the counterface material has the same or
similar thermal conductivity. Two polymers in sliding
contact will normally operate at significantly reduced
speeds than a polymer against a metal surface. The wear rate
of polymer composites is highly dependent upon the surface
roughness of the metal counterfaces. In the initial
operating stages, wear is significant but can be reduced by
providing smooth counterfaces. As the run-in period is
completed, the wear rate is reduced due to polymer film
transfer or by polishing action between the sliding
surfaces. Environmental factors also influence wear rate.
Increased relative humidity inhibits transfer film formation
in polymer composites such as PTFE, which rely on transfer
film formation on counterfaces. The presence of hydrocarbon
lubricants may also produce similar effects. Composites such
as nylons and acetals, which do not rely on transfer film
formation, experience reduced wear in the presence of small
amounts of hydrocarbon lubricants.
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