ISSN   1004-0595

CN  62-1224/O4

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凹凸棒石增强聚酰亚胺复合材料的干摩擦性能研究

Tribological Performance of Attapulgite Reinforced Polyimide Composites under Dry Friction Condition

  • 摘要: 本文中研究制备了聚酰亚胺(PI)多元纳米复合材料,系统考察了多元纳米复合材料在干摩擦条件下的摩擦学性能,并通过扫描电子显微镜(SEM)、光学显微镜(OM)、X射线光电子能谱(XPS)、红外光谱(ATR-FTIR)和拉曼光谱(Raman)对转移膜的微观形貌和化学成分进行系统分析. 摩擦学试验结果表明,与传统碳纤维/石墨(CF/Gr)增强的聚酰亚胺复合材料相比,凹凸棒石(ATP)增强的聚酰亚胺多元纳米复合材料具有更佳的减摩抗磨性,其磨损率降低约69%. 结果分析表明在摩擦热和摩擦应力作用下,ATP的摩擦化学产物MgO、SiOx和Al2O3与PI分子链段以及石墨碳在摩擦界面发生摩擦烧结,在金属对偶表面形成含有陶瓷微晶的高质量转移膜,显著提升PI复合材料在干摩擦条件下的减摩抗磨性能. 本研究为制备耐高温和长寿命高端摩擦部件提供研究基础.

     

    Abstract:
    Operating environments of mechanical motion components become increasingly harsh with rapid development of modern transportation and other industrial activities. Friction and wear are main causes of shorten service life and weaken safety and reliability of equipment, thus causing safety accidents in serious cases. Polymer-based composites have been developed increasingly for self-lubricating materials by virtue of their lightweight, superior tribological performance, high specific strength, improved corrosion resistance and thermal stability. Numerous high-performance self-lubricating composites were formulated for different sliding contact conditions. Nevertheless, the majority of self-lubricating polymer composites were not suitable for operation at higher service temperature, i.e. even polyether ether ketone-based composites only service at 260 ℃. Polyimide (PI) is an outstanding engineering material with service temperature of 300~500 ℃. While, the poor wear resistance and anti-friction properties of pristine PI severely limit its further applications in harsh motion conditions. Attapulgite is a hydrous layer-ribbon magnesium aluminum silicate clay mineral having a fibrous morphology. Components and crystal structures of attapulgite are very similar to that of serpentine, whereas the cost of attapulgite is much lower because of its natural abundance and simplicity for refining. Moreover, researchers reported modified attapulgite as oil additives exhibit excellent lubricating performance, which ascribed to growth of a robust tribofilm on steel surface during sliding process. Although tribological performance of polymer composites reinforced with attapulgite have been investigated in several pioneering works, effect of attapulgite on tribo-performance of conventional carbon fiber (CF)-reinforcing PI composites has not been studied yet. In particular, comprehensive understanding of complex physio-chemical actions of attapulgite and PI at dry sliding interface is still lacking.
    Herein, three different polyimide (PI)-based composites (PI+10CF/Gr, PI+10CF/Gr+5ATP and PI+10CF/Gr+5SiO2) were prepared and their tribological properties under dry friction conditions were investigated using a Pin-on-Disk (POD). The microscopic morphologies and chemical compositions of tribofilms and worn composites’ surfaces were further characterized with scanning electron microscope (SEM) and optical microscope (OM). Friction experiments demonstrated that compared with conventional PI+10CF/Gr composite, the friction and wear of PI+10CF/Gr+5SiO2 and PI+10CF/Gr+5ATP were greatly reduced under higher PV valves (PV value=3, 5 and 7 MPa·m/s). In particular, PI+10CF/Gr+5ATP improved wear resistance by up to 69% and 50% compared to PI+10CF/Gr and PI+10CF/Gr+5SiO2 under PV value of 3 MPa·m/s. SEM graph of worn steel surface demonstrated that the entire surface areas of the metallic disc including of original grooves were covered by transferred material after being rubbed against PI+10CF/Gr+5ATP. The tribo-oxidation of steel surface was inhibited with incorporation of ATP filler. X-ray photoelectron spectroscopy (XPS), attenuated total reflection infrared spectroscopy (ATR-FTIR) and Raman spectrometer (Raman) analyses revealed that ATP undergoes tribo-chemical reactions under friction heat and shear stress, and its tribo-chemical products, i.e MgO, SiOx and Al2O3 nanocrystals tribo-sintered with PI molecular chain segments and graphitic carbon, forming a“high quality”tribofilm with high load-carrying ability, which significantly improved the friction and wear resistance of PI composites. This study will provide a foundation for future researches of high temperature-resistant and long-life tribo-materials.

     

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