Polymer Formation on Sliding Metals in Air Saturated with Organic Vapors

An exploratory study is made of the lubricating properties of polymer formed in the wear track by mechanical activation during continuous slide between palladium and palladium, chromium and chromium, and steel and steel, in air saturated with the vapor of various volatile organic compounds. Contrary to expectations from pioneer studies, polymer which forms on palladium in air saturated with limonene and disobutylene does not appear to reduce wear appreciably, and no polymer forms in air saturated with benzene. When a rubbed monolayer of stearic acid is present on the palladium surface, copious polymer formation takes place and wear and friction are reduced. No polymer forms on chromium or steel in any environment. Operation in o-chlorbenzotrifluoride results in wear reduction with all three metals, that with palladium and iron being very great, but no observable polymer is formed in any case. It is concluded that the nature of the adsorbed film which precedes the formation of polymer is the main determining factor in wear and friction reduction. The results are explained by assuming that free radicals, produced by shearing an adsorbed film in the presence of a catalyst, initiate polymer formation.