Tribology of amorphous polymers in heavy-duty applications

The potential of amorphous polymers in heavy-duty tribological applications are less explored. We have attempted to explore the governing mechanism in the wear behavior of behavior of amorphous polymers. In this research, tribological investigations are performed for amorphous polymers such as Polycarbonate (PC), Polyetherimide (PEI) and Polyphenylsulfone (PPSU). Moreover, Polyethylene terephthalate (PET) is also chosen as a reference material from the semi-crystalline group. Large scale wear tests were performed with a flat-on-flat configuration with 4 MPa contact pressure and 50 mm/sec sliding speed. Among the four polymers, PC and PEI had similar wear performance with increased wear rate. However, within the amorphous group, PPSU has better wear performance. Nevertheless, PPSU has increased wear rate when compared with semi-crystalline PET. All three amorphous polymers has flaky wear debris, however this was not prevalent in the semi-crystalline PET. Significant amount of debris were found in PC and PEI when compared with PPSU and PET. The poor performance of PEI and PC can be attributed to wear mechanism and interfacial behavior. The material removal process in the amorphous polymer represent a peeling mechanism where flaking of consecutive layers was evidenced. Amorphous polymers due to its meagre plastic flow characteristics evades adhesion and thereby hindering the formation of transfer layer. The inability to form the protective transfer layer is the main reason for poor wear performance of PC and PEI. In the morphological investigation, PPSU and PET had significant amount of transfer layer and hence better wear performance. This concludes that the governing mechanism in the wear performance of amorphous polymer relies on the capability of transfer layer formation. This paper attempts to relate the material characteristics to transfer layer formation.

Publication year:2016