Huimin Qi1, Ligang Zhang2, Ga Zhang3, Tingmei Wang2, Qihua Wang2. 1. State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China; University of Chinese Academy of Sciences, Beijing 100049, China. 2. State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China. 3. State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China; Qingdao Center of Resource Chemistry & New Materials, Qingdao 266071, China. Electronic address: gzhang@licp.cas.cn.
Abstract
HYPOTHESIS: Tribochemical reactions of polymer matrix with steel counterpart can exert an important role in tribofilm's structure, and thereby affect the tribological performance of its composites. EXPERIMENTS: In the present work, tribochemistry of ultrahigh molecular weight polyethylene (UHMWPE), polyphenylene sulfide (PPS) and polyetherimide (PEI) in tribo-composites was comparatively studied. Two kinds of formulations, i.e. conventional composites filled with carbon fibers and graphite and hybrid nanocomposites containing additional silica (SiO2) nanoparticles, were investigated. FINDINGS: It was revealed that when rubbing with steel, molecular chains of UHMWPE were broken and free radicals finally chelated with the counterface. Whereas, PPS molecules underwent thermal decomposition, oxidation and finally ferrous sulfide (FeS) and ferric sulfate [Fe2(SO4)3] were generated. Chelating reaction of PEI was identified only for sliding of PEI-based nanocomposite. Tribochemistry of polymer molecules played an important role in tribofilm formation and tribological performance of the conventional composites. When sliding took place with the hybrid nanocomposites at low pv conditions, tribochemistry of polymer molecules played a similar role as for the conventional composites. Nonetheless, at high pv conditions, independent on the polymer matrices, robust tribofilms containing high fraction of silica were generated on the steel counterface, minimizing direct rubbing of the friction pair.
HYPOTHESIS: Tribochemical reactions of polymer matrix with steel counterpart can exert an important role in tribofilm's structure, and thereby affect the tribological performance of its composites. EXPERIMENTS: In the present work, tribochemistry of ultrahigh molecular weight polyethylene (UHMWPE), polyphenylene sulfide (PPS) and polyetherimide (PEI) in tribo-composites was comparatively studied. Two kinds of formulations, i.e. conventional composites filled with carbon fibers and graphite and hybrid nanocomposites containing additional silica (SiO2) nanoparticles, were investigated. FINDINGS: It was revealed that when rubbing with steel, molecular chains of UHMWPE were broken and free radicals finally chelated with the counterface. Whereas, PPS molecules underwent thermal decomposition, oxidation and finally ferrous sulfide (FeS) and ferric sulfate [Fe2(SO4)3] were generated. Chelating reaction of PEI was identified only for sliding of PEI-based nanocomposite. Tribochemistry of polymer molecules played an important role in tribofilm formation and tribological performance of the conventional composites. When sliding took place with the hybrid nanocomposites at low pv conditions, tribochemistry of polymer molecules played a similar role as for the conventional composites. Nonetheless, at high pv conditions, independent on the polymer matrices, robust tribofilms containing high fraction of silica were generated on the steel counterface, minimizing direct rubbing of the friction pair.
Authors: Sergey V Panin; Jiangkun Luo; Dmitry G Buslovich; Vladislav O Alexenko; Lyudmila A Kornienko; Anton V Byakov; Vitaly N Paimushin; Artur R Shugurov Journal: Molecules Date: 2022-09-27 Impact factor: 4.927