Tribological Properties Of PMMA Based Composites Filled By PTFE, Cu And Al₂O₃

Compared with metals and ceramics,polymers are widely used as the friction pair materials in mechanical parts such as bearings,bushings,seals and brake pads due to their unique performances.Poly（methyl methacrylate）（PMMA）is a kind of thermoplastic polymer material with excellent properties,but pure PMMA has the high friction coefficient and poor wear-resistant,which greatly limits its application in the field of tribology.Improving the anti-friction and wear-resistance properties of PMMA is an important research direction in polymer tribology,and filling modification is one of the crucial methods to improve the tribological properties of composites.Therefore,the research of the law and mechanism of the friction and wear of PMMA matrix composites under the synergistic action of single or multiple fillers has an important theoretical significance in tribology and application value in engineering.PMMA matrix composites which separately or synergistically filled with PTFE,Cu and Al₂O₃ are prepared by self-curing at room temperature.Composition and thermodynamic analysis of filled modified PMMA matrix composites were done by Differential Scanning Calorimetry（DSC）,Fourier Transform Infrared Spectrometer（FT-IR）and Field Emission Scanning Electron Microscope（FE-SEM）etc.The ball-on-disk tribometer and conscan confocal optical profilometer were used to study the effects of filler types,ratios,heat treatment processes and working conditions on the friction and wear behaviors and mechanisms.The research indicates:（1）Compared with Cu or Al₂O₃,filling PTFE alone can significantly reduce the friction coefficienst and wear rates of PMMA matrix composites.When the powder/liquid ratio is P/L=1.5 and PTFE filling mass ratio is 25wt%,PTFE/PMMA composites show better friction coefficient and wear-resistance.（2）PTFE plays an important role in reducing the friction coefficients and wear rates of PMMA matrix composites filled with PTFE/Cu/Al₂O₃,and the effect of Cu is minimal or even negligible.The lower friction coefficients of PMMA matrix composites filled with PTFE/Cu/Al₂O₃ appear when the combination of the mass ratio of PTFE is larger than about 4.5wt%and the mass ratio of Al₂O₃ is lower than approximately 7.5wt%.And the lower wear rate appears when the combination of the mass ratio of PTFE is larger than about 5wt%and the mass ratio of Al₂O₃ is lower than approximately 8wt%（it does not include that PTFE is greater than about 8.5wt%and Al₂O₃ is less than about 1.5wt%）.（3）Compared with the unheated treatment PTFE/PMMA composites,the heat treatment process obvious enhances the wear-resistance of PTFE/PMMA composites,while it has little effect on the friction coefficients.The lower wear rates of PTFE/PMMA composites appear when the molding pressure is 15MPa,the molding temperature is110°C,and the molding time is 15min.（4）The friction coefficients and wear volumes of PTFE/PMMA composites are completely different with the variation of working conditions.The friction coefficients of PTFE/PMMA composites decrease with the increasing of load and increase with the increasing of velocity.The wear volumes of PTFE/PMMA composites rise with the increasing of load and velocity.