Molecular Mechanisms of Polyoxymethylene Wear

Friction and wear of polyoxymethylene upon friction against polyoxymethylene and polyetheretherketone have been analyzed. It is shown that wear exponentially increases upon growth of contact pressure and sliding velocity in the homogeneous friction pair polyoxymethylene–polyoxymethylene. In the heterogeneous pair polyetheretherketone–polyoxymethylene the wear of POM is small and exhibits no registered dependence on sliding velocity and contact pressure. Mass-spectrometric analysis shows that the macromolecular decomposition products are not detected for polyetheretherketone–polyoxymethylene pair. However, for thermodynamically compatible polyoxymethylene–polyoxymethylene pair their formation, accompanied by the growth of friction force, is detected already at the levels of friction power as low as 10^–2 MPa m/s. These differences have been interpreted to result from interpenetration of polyoxymethylene macromolecules across the interface and their rupture in the shear field in homogeneous polyoxymethylene–polyoxymethylene friction pair and its absence in polyetheretherketone–polyoxymethylene pair. Thermally activated interpenetration of macromolecules for polyoxymethylene–polyoxymethylene pair and its absence in polyetheretherketone–polyoxymethylene pair has been visualized by means of molecular dynamics simulations. The experimental approach and the results of its application will be useful in detailed studies of molecular level friction mechanisms of friction and wear of industrially used polymers and their composites.