[题名] 聚[四氟乙烯-共-（全氟烷基乙烯基醚）]（PFA）磨损引起的微观结构和化学变化

[作者] Mark A. Sidebottom, Christopher P. Junk,Holly L. S. Salerno, Heidi E. Burch,Gregory S. Blackman,and Brandon A. Krick

[摘要] 摩擦诱导的剪切应力和磨损会导致聚四氟乙烯-共-(全氟烷基乙烯基醚)，也称为全氟烯烃聚合物（PFA）发生微观结构和化学变化。了解这些变化对于将PFA用作摩擦材料至关重要。通过摩擦学（摩擦和磨损）实验，结合差示扫描量热法、X射线衍射和红外光谱，可以表征PFA磨损碎片与基体的微观结构和化学差异。PFA磨损碎片在较低温度下从三斜晶转变为六方晶结构，其结晶度高于基体PFA。分子取向受剪切驱动可能是这些微观结构发生变化的原因。PFA磨损碎片的分子量降低，可通过游离羧酸的存在得到证实。分子量降低可能是由于在微观结构的无定形区域中，PFA主链的剪切驱动链断裂所致。在PTFE的磨损中观察到分子量降低和结晶度增加的现象，这支持了摩擦化学驱动机制在氟聚合物-氧化铝复合材料中实现超低磨损。

[关键词] PFA、摩擦诱导、剪切应力、磨损碎片

[Title] Wear-Induced Microstructural and Chemical Changes inPoly [tetrafluoroethylene-co-(perfluoroalkyl vinyl ether)] (PFA)

[Author] Mark A. Sidebottom, Christopher P. Junk,Holly L. S. Salerno, Heidi E. Burch,Gregory S. Blackman,and Brandon A. Krick

[Abstract] Friction-induced shear stress and wear of poly[tetrafluoroethylene-co-(perfluoroalkyl vinyl ether)], also known as perfluoroalkoxy polymer (PFA), causes microstructural and chemical changes. These changes are essential to understand PFA as a tribological material. Tribological (friction and wear) experimentation coupled with differential scanning calorimetry, X-ray diffraction, and infrared spectroscopy was used to characterize the microstructure and chemical differences in PFA wear debris versus bulk. PFA wear debris transitioned from triclinic to hexagonal crystalline structure at lower temperatures and had increased crystallinity versus bulk PFA. Shear-driven molecular alignment was the likely cause of these microstructural changes. Reduced molecular weight of PFA wear debris was confirmed by the presence of free carboxylic acids. Reduced molecular weight is likely due to shear-driven chain scission of the PFA backbone within the amorphous region of the microstructure. Reduced molecular weight and increased crystallinity are observed in wear of PTFE and support the tribochemically driven mechanism for ultralow wear fluoropolymer−alumina composites.

[Keywords] PFA、Friction-induced 、 shear stress、A wear debris