γ辐照诱导表面氧化对聚醚醚酮（PEEK）摩擦学性能的影响
Infuence of gamma irradiation‑induced surface oxidation on tribological property of polyetheretherketone (PEEK)
Liqiang Chai，Beibei Zhang，Li Qiao，Peng Wang，Lijun Weng
DOI：10.1007/s00289-021-03825-4
文章链接：
https://link.springer.com/article/10.1007/s00289-021-03825-4
摘要：
本文研究了被剂量高达20MGy的伽马射线照射过后的半结晶材料PEEK表面降解和内部结构变化对其摩擦学行为的影响。通过X射线光电子能谱分析发现受照射的PEEK样品表面上C=O和O-C=O官能团的百分比含量增加，这表明PEEK表面降解主要形式是辐射诱导的氧化导致的。通过扫描电镜结果发现，当辐照剂量超过10 MGy时，PEEK样品会出现微孔、微裂纹等表面形貌缺陷，同时摩擦实验发现，由于表面氧化层的存在，辐照后的PEEK表面静摩擦系数增大。此外，当剂量超过1MGy时，辐照后PEEK表面的稳态动摩擦系数逐渐降低。表面氧化产物起三体滚动作用，导致动摩擦系数下降。然而，与未辐照样品相比，相应的磨损率增加了一个数量级。
关键词：伽马辐照；表面氧化；PEEK；摩擦磨损
Abstract:
In this paper, the semicrystalline PEEK was irradiated in the atmosphere by gamma rays with a dose up to 20 MGy. The influence of the surface degradation and the internal structural changes on the tribological behavior of PEEK was investigated. X-ray photoelectron spectroscopy analysis shows an increase in the percentage of C=O and O–C=O functional groups on the surface of irradiated PEEK samples. It reveals that irradiation-induced oxidation is the primary form of degradation on the PEEK surface. Scanning electron microscopy results indicate that the surface morphology defects such as micropores and microcracks appear when the irradiation dose exceeds 10 MGy. The friction experiments show that the static friction coefficient of the irradiated PEEK surface increases due to the existence of the surface oxide layer, and the appearance of a shorter run-in period attributes to the formation of uniform and stable transfer film in the initial stage of friction. In addition, when the dose is more than 1 MGy, the steady-state dynamic friction coefficient of the irradiated PEEK surface gradually decreases. The surface oxidation products play a rolling effect of three bodies, resulting in the fall of the dynamic friction coefficient. However, the corresponding wear rate increases by one order of magnitude compared to that of the unirradiated sample.
Keywords：Gamma irradiation；Surface oxidation；PEEK；Friction and wear
图1 原始和 20 MGy 剂量辐照 PEEK 的表面和转移膜的拉曼光谱
图2 不同辐射剂量前后PEEK去除氧化层的磨损率
图3 不同辐照剂量去除氧化层前后PEEK的平均稳态摩擦系数。插图显示去除氧化层前后PEEK a和b的相应摩擦系数曲线
结论：在这项工作中，研究了环境空气中高达20MGy剂量的伽马射线辐照PEEK的表面和内部结构的变化。还详细讨论了伽马辐射引起的表面降解对PEEK摩擦学性能的影响。可以得出以下结论：
1.辐射引起的氧化是PEEK表面降解的主要形式。随着辐照剂量的增加，表面出现氧化降解层，表面形貌缺陷增多。
2.力学性能测试表明，辐照氧化导致PEEK表面硬度降低。
3.摩擦结果表明，辐照氧化导致静摩擦系数增大，动摩擦系数减小。表面氧化产物起三体滚动作用，导致动摩擦系数下降。
4.辐照后PEEK的磨损率在1MGy以上时增加。辐照诱导的表面微缺陷和氧化簇引起的磨粒磨损导致辐照后 PEEK 在高剂量下的耐磨性下降。
Conclusions:
In this work, the changes of surface and internal structure of PEEK irradiated by gamma ray up to 20 MGy dose in the ambient air are studied. The infuence of gamma irradiation-induced surface degradation on tribological property of PEEK is also discussed in detail. The conclusions can be drawn as follows:
1. Irradiation-induced oxidation is the primary form of degradation on the PEEK surface. As the irradiation dose increases, surface oxidation degradation layers appear and the surface morphology defects increase.
2. The mechanical performance test shows that irradiation-induced oxidation results in a decrease in the surface hardness of PEEK.
3. The friction results show that the irradiation-induced oxidation leads to an increase in the static friction coefcient and a decrease in the dynamic friction coefcient. The surface oxidation products play a rolling efect of three-body resulting in the fall of the dynamic friction coefcient.
4. The wear rate of the irradiated PEEK increases when the dose is more than 1 MGy. Irradiation-induced surface microdefects and the abrasive wear caused by oxidized clusters result in the deterioration of wear resistance of the irradiated PEEK at high doses.
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