Studies On The Tribological Properties Of Polymer-Polymer Combinations

The metal-polymer combination have been increasingly replaced by the polymer-polymer combination because of its low weight and low-friction nature, while little attention has been paid on the friction and wear properties of polymer-polymer sliding combinations, and the studies on this field are still unsystematic and insufficient.In this study, the researching systems were divided into thermoplastic/thermo-plastic, thermoplastic/thermosetting and thermosetting/thermosetting combinations. Several polymers, such as thermoplastic polyphenylene sulfide (PPS), polycarbonate (PC), polyamide 66 (PA66) , high density polyethylene (HDPE) and polytetrafluoro-ethylene (PTFE), and thermosetting epoxy (EP), phenol formaldehyde (PF), were selected as researching materials in order to study the friction and wear behaviors of polymer-polymer combinations systematically. The structure and morphology of worn surface and debris were analyzed with the aid of Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectrometry (FT-IR), Differential Scanning Calorimetry (DSC), etc. On the basis of the results of tribological tests and surface analyses, the relationships between the tribological behaviors and the cohesive energy density (CED), hardness, the surface physical state, as well as the mechanisms of friction and wear of polymer-polymer combinations were detailed discussed. The researching results will deepen the understanding on the polymer tribology and enrich the tribological theories.The followings are some innovative conclusions obtained from this study:1．The CED of the two mated polymers affected the friction and wear properties of the polymer-polymer combinations. For the similar polymer combinations, the increasing CED of the polymers associated with an increasing friction coefficient but a decreasing specific wear rate. For the dissimilar polymer combinations, the friction coefficients decreased with the increasing absolute value of CED difference of the two mated polymers, the specific wear rate of a polymer increased with the increasing CED of the mated polymer.2．The tribological properties of thermoplastic-thermosetting combinations had no obviously relationship with the CED, but they were influenced by the hardness of polymers. The friction coefficients decreased with the increasing absolute value of hardness difference of the two mated polymers, the specific wear rate of a polymer increased with the increasing hardness of the mated polymer.3．Physical state markedly influenced the friction and wear behaviors of polymer-polymer combinations. Low friction and wear were observed when two polymers both were in the glass state, the friction and wear increased when polymers were in the viscous elastic state. The friction decreased and the wear increased sharply in the viscous flow state. The tribological behaviors were commonly decided by the polymer with poor heat resisting property when the two mated polymers were in different physical state.4．The friction and wear properties of polymer-polymer combinations were influenced by the chain flexibility of polymers. For the self-mated polymer combinations, the higher the chain flexibility was, the poor dependence of tribological behaviors on the sliding conditions was. For the dissimilar polymer-polymer combinations, the tribological behaviors dependence on the sliding conditions were decided by the polymer with high chain flexibility, this result might be due to the easily orientation for polymer chain along the friction force direction for the polymer with high chain flexibility.