Wear resistance effects of alumina and carbon nanoscale fillers in PFA, FEP, and HDPE polymers
Wear resistance effects of alumina and carbon nanoscale fillers in PFA, FEP, and HDPE polymers
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DOI：
10.1016/j.wear.2022.204376
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发表时间：
2022-05-22
期刊：
影响因子：
5
通讯作者：
Blanchet, Thierry A.
中科院分区：
文献类型：
--
作者：
Makowiec, Mary E.;Gionta, Grace L.;Blanchet, Thierry A.
在大量研究表明，纳米结构α-氧化铝填料能够将聚四氟乙烯(PTFE)极高的磨损率降低到远低于传统PTFE微复合材料的极小值(~10(-7)mm(3)/Nm)后，最近的几项研究也表明，α-氧化铝填料能够赋予另一种氟聚合物--全氟烷氧基(PFA)共聚物类似的性能，否则在未填充状态下，PFA同样缺乏耐磨性。除了在PFA中复制这种α-氧化铝的性能外，在这项研究中，还使用纳米碳粉展示了这种极端的减磨能力，作为代表几种其他形式的纳米级碳填料的例子，与α-氧化铝一样，已经被证明能够提供对聚四氟乙烯的极端抗性。含氟乙烯丙烯(FEP)共聚物的纳米复合材料以前从未被摩擦学探索过，因此本文不仅用α-氧化铝和纳米碳，而且用其他纳米管(CNT)和介孔形式的纳米碳填料对其进行了更充分的研究。在初步测试中，只有α-氧化铝对FEP具有减磨能力；当α-氧化铝浓度为2wt%时，磨损率为~0.8×10(-6)mm(3)/Nm。虽然这是一个令人印象深刻的磨损率下降，但它并不是非常极端的下降，如在聚四氟乙烯或聚四氟乙烯或聚四氟乙烯。纳米碳粉在聚四氟乙烯和聚四氟乙烯中的传输更不完全，在FEP中的传输不完全，未填充的FEP磨损率仅为10-5 mm(3)/Nm，而碳纳米管和介孔碳的传输效果更差。相应地，FEP磨损表面的ATR-FTIR谱显示出相当大的峰，表明已知的化学相互作用与PTFE和PFA的耐磨性有关，只有在耐磨性最好的α-氧化铝情况下，纳米碳的耐磨性较小。最后，研究表明，这种填料只有在原本缺乏耐磨性的聚合物中才表现出如此强烈的有益效果，而对于高密度聚乙烯(HDPE)等已在未填充状态下具有一定内在耐磨性的聚合物实际上可能是有害的。
Following numerous studies demonstrating the ability of nanostructured alpha-alumina filler to reduce the prohibitively high wear rate of polytetrafluoroethylene (PTFE) down to extremely small values (~ 10(-7) mm(3)/ Nm) well below those of conventional PTFE micro-composites, alpha-alumina filler was also shown capable, in a couple recent studies, of imparting similar performance to another fluoropolymer, perfluoroalkoxy (PFA) copolymer, which otherwise was similarly lacking wear resistance in the unfilled state. In addition to duplicating such alpha-alumina performance in PFA, in this study such an extreme wear-reducing capability has also been demonstrated using nanocarbon powder, as an example representative of several other forms of nanoscale carbon filler that like alpha-alumina had been shown capable of providing extreme resistance to PTFE. Fluorinated ethylene propylene (FEP) copolymer, whose nanocomposites have not been tribologically explored previously, was thus more fully investigated here with not only alpha-alumina and nanocarbon, but also other nanotube (CNT) and mesoporous forms of nanoscale carbon fillers. In preliminary testing, only the alpha-alumina filler indicated an ability to impart its wear-reducing capability to FEP; a wear rate of ~0.8 x 10(-6) mm(3)/Nm was observed at 2 wt% alpha-alumina concentration. While this is an impressive reduction in wear rate, it is not quite as extreme a reduction as that observed in PTFE or PFA. The transport of the extreme wear resistance of nanocarbon powder in PTFE and PFA was even more partial and incomplete in FEP, with the ~0.3 x 10(-3) mm(3)/ Nm unfilled FEP wear rate only reduced to ~10(-5) mm(3)/Nm, while the CNT and mesoporous carbon fillers were even less effective. Correspondingly, ATR-FTIR spectra from FEP wear surfaces displayed sizable peaks evident of the chelation of chemical interactions known to be associated with wear resistance for PTFE and PFA matrices only in the most wear-resistant alpha-alumina case and to a lesser extent for the nanocarbon. Finally, it is demonstrated that such fillers demonstrate such strongly beneficial effects only in polymers that otherwise lack wear resistance, and may actually be deleterious for polymers such as high density polyethylene (HDPE) already having some inherent wear resistance in their unfilled state.