Tribochemical Transformations in Polymer-Metal Systems

Let us examine the chief t3rpes of tribochemical transformations occurring during friction of different classes of pol3miers paired with a steel counterbody [88]. 

Phenol formaldehyde resins (pol3miethylene phenylene) are polymers with irregular cross-linked structure. During friction of resol- and novolac-t3rpe phenol formaldehyde pol3miers two processes take place simultaneously, namely structuring (aftercure) via recombination of weak ester groups 

In the case of friction of thermostable polyphenylen oxides (PPO) containing substituted aromatic nuclei in macromolecules, mainly cresol and small amounts of xylenol are derived. As a result, a secondary heat resistant structure is formed on the friction surface of PPO parts. The material with a hybrid structure of caged snake type based on PPO in combination with polymaleimide displays better wear resistance owing to its cross-linked structure. The tribochemical lubrication in such pairs is produced via tribological decomposition of less heat-resistant polymers [98]. 

Rubbing of polyarylene etheroketone (PAEK) containing ether links in its backbone chain, a carbonyl group and aromatic nuclei is accompanied by destruction along mainly ether links and structuring processes. Formation of stable transfer films on the steel counterbody leads to friction between polymer layers with the effect of self-lubrication that lowers the friction coefficient and heightens wear resistance of PAEK as compared to PPO [99]. 

Polyamides. Wear resistance of polyamides (PA) of different chemical structures is to a great extent determined by the nature of the tribochemical processes, which in turn depends largely on the chemical constitution of the PA links, location of the amide bonds, the structure of the end groups, chains and frictional conditions [86,100,101]. 

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