γ射线辐照对PA66结构和摩擦学性能的影响

Effects ofγ-ray Irradiation on Structure and Tribological Properties of PA66

目的研究辐照后PA66的分子结构和摩擦学性能变化情况,以及两者之间的联系。方法采用凝胶含量测试、红外光谱测试、XPS测试分析、DSC测试分析等方法研究辐照前后PA66的分子结构变化情况,将辐照前后各剂量PA66以球-平面形式进行往复式摩擦磨损试验,对摩擦因数、磨损率及磨痕形貌进行分析,以研究辐照对PA66摩擦学性能的影响。结果随着辐照剂量的增加,PA66凝胶的质量分数从1.31%增加到60.77%,辐照导致PA66表面含氧官能团含量增加,且在1000kGy剂量下生成了羟基,同时材料结晶度整体随辐照剂量的增加而降低。经辐照后,PA66的摩擦因数从0.49逐渐增至0.615,磨损率从179.3×10^(3)μm^(3)/(N·m)大幅增至2511.7×10^(3)μm^(3)/(N·m)。磨痕中央和边缘的磨损形式的变化趋势不同,磨痕中央始终为黏着形貌,磨痕边缘在剂量增大后从黏着形貌变化为沟壑状形貌。结论PA66在γ射线辐照影响下主要发生分子链间的交联和表面氧化,分子间的交联和辐照破坏了材料内晶体的结构,导致材料的结晶度下降。同时,PA66交联使对磨副运动时剥落表面材料受到更大的阻力,导致材料在黏着和犁削过程的剥落体积更大,经辐照后PA66的摩擦因数上升、磨损率增大。

The work aims to study the molecular structure and tribological properties of PA66 irradiated by gamma rays at different doses in atmospheric environment,so as to understand the change trend of tribological properties of PA66 under irradiation environment,and link the macroscopic changes of tribological properties with the microscopic changes at molecular scale,hoping to provide references for the application of PA66 in irradiation environment.PA66 was irradiated by gamma rays at doses of 50,100,250,500 and 1000 kGy in atmospheric environment,respectively.The changes of functional groups of PA66 were monitored by infrared spectroscopy and X-ray photoelectron spectroscopy,and the degree of molecular cross-linking and crystallization was evaluated by gel content test and differential scanning calorimetry.The tribological test was carried out by blocky PA66 and 6 mm diameter metal ball with reciprocating motion,and the friction coefficient during the test was obtained.Combined with the wear rate and wear morphology,the tribological properties and wear mechanism changes of PA66 before and after irradiation were analyzed.The results showed that the gel content of PA66 was 1.31%when untreated,and increased to 60.77%after gamma ray irradiation to 1000 kGy,indicating that the molecular chains of PA66 were mainly cross-linked underγ-ray treatment.The results of infrared spectroscopy and X-ray photoelectron spectroscopy showed that the surface oxidation degree of PA66 increased with the increase of irradiation dose,and a new hydroxyl functional group was formed at 1000 kGy.The crystals of PA66 were damaged by gamma ray.The degree of crystallization of the material obtained by DSC test was 30.78%under the unirradiated condition,and slightly decreased to 25.07%when the dose reached 1000 kGy.The tribological properties of PA66 deteriorated significantly with the increase of irradiation dose,the friction coefficient increased from 0.49 to 0.615,and the depth and width of the wear tracks increased from 34.8μm and 796μm to 174.6μm and 2225μm,respectively.When the radiation dose did not reach 500 kGy,the wear mechanism of the entire wear track was adhesion and plough cutting.When the radiation dose reached 500 kGy,the wear mechanisms of the center and edge of the PA66 wear track were significantly different.The material at the center of the wear track was still lost in the form of adhesion and plough cutting,the wear mechanism at the edge of wear track changed to fatigue wear because the new cracks were connected with the cracks generated by irradiation.Although the wear mechanism of the center of the wear track is the same before and after irradiation,the self-lubrication property of PA66 is weakened due to the change of the cross-linking degree of the material after irradiation,and the morphology of the center of the wear track is changed.The increase of single wear debris with the increase of radiation dose can support the deterioration of tribological properties of PA66 due to the increase of cross-linking degree.