| Recently, research on polymer tribology has developed into the molecular level.As we know, the various macroscopic properties of any material, in the final analysis,are determined by its microscopic structure. The tribological property of polymer isclosely related to its structure. Many intrinsic factors influence wear and frictionperformance, such as the size of molecular weight, the difference of molecular structure(linear, branched or crosslinked), the type of polymer (thermoplastic or thermosetting,crystalline or non-crystalline, etc.) and the difference of crystal form and crystallinity.As research about decreasing the friction coefficient and improving the wear-resistanceof the resin has become a spotlight, changing the molecular structure would be anexcellent place to start.Poly (aryl ether ketone)(PAEK) resins are considered as widely used engineeringmaterials possessing linear aromatic structure in the main chain, which always haveoutstanding performance in the aspects of manufacturing, heat-resistance, wear-resistance, chemical resistance and mechanical properties. Among various PAEKpolymers, poly (ether ether ketone)(PEEK) is a representative increasingly used intribological field owing to its excellent merits such as good wear-resistance and self-lubricating, excellent thermal stability and high mechanical properties, etc. In recentyears, numerous researches on improving wear resistance and decreasing frictioncoefficient of PEEK material have been conducted. However, most of the work focuson improving tribological performance by adding other components like solidlubrications and reinforcements into the pure resin, rather than by designing molecularstructure of resin itself.Poly (ether ether ketone ketone)(PEEKK) develops from PEEK, which is ofhigher heat-resistance level. As soon as it is figured out that it is the increasing of thecontent ratio of rigid carbonyl to flexible ether in the main chain makes PEEKK possessbetter thermostability, other rigid groups like biphenyl begin to be concerned in thesynthesis design. Poly ether ether ketone ketone containing biphenyl (PEBEKK) was then synthesized and it proved that strengthening stiffness of the polymer chain isconducive to the improvement of heat-resistance level of resin. However, reports onPEBEKK mainly focuse on the synthesis, thermal property and crystal structure, otherproperty details especially about tribology have not been further reported. The aim ofthis study was to figure out how and even why the rigid biphenyl group could affectwear and friction property of PAEK resins. Furthermore, guidance for similar synthesisexperiments to obtain self-lubricating pure PAEK resins in the future could be given bythe research results.First, a series of biphenyl containing poly (arylene ether ketone) copolymers weresynthesized by nucleophilic substitution polycondensation. The content of biphenylunits in polymer chains was controlled by the feed ratio of biphenol and hydroquinonemonomers. The dependence of tribological property on biphenyl content wasinvestigated. With the increase of biphenyl group content, the friction coefficient ofcopolymers initially decreased and gradually increased after BP60, while the changingregularity of wear rate performed in reverse with it. In part, the outcome iscorrespondent with changes of crystallinity. Good correlations could be obtained inpolymer structure, crystallinity and friction performance.In the next work, we prepared a CF20/BP60composite which was of very lowfriction coefficient and high wear-resistance. According to our basic work, the optimalweight content of CF is20%, at which friction and wear performance of the resinswould be the best. As a result, we combined BP60with20%weight content of CF andstudied the friction and mechanical properties of the composite. The results show thatthe prepared BP60/CF20composite is of lower friction coefficient than pure BP60, andalso the ability of the wear resistance is improved greatly. What’s more, the compositematerial is of great thermal stability and excellent mechanical properties. |
PDF Full Text Request