利用力学试验、衰减全反射红外光谱技术(ATR-FTIR)、热重分析法(TG)、差示扫描量热法(DSC)、凝胶渗透色谱(GPC)、扫描电子显微镜(SEM)比较研究了3种不同结晶度高密度聚乙烯(HDPE)的光氧老化特性,分析了结晶度对HDPE力学性能、化学结构、热稳定性、熔融特性、分子量和表面微观形貌的影响规律.结果表明结晶度越高,HDPE弯曲强度、弯曲模量和冲击强度下降最明显;不饱和度增长越剧烈,支化作用和断链作用更明显,且区别主要集中于老化初期;羰基指数和羟基指数增长越快,热分解特征温度下降最明显,热稳定性下降更强烈,但熔融特征温度和氧化诱导温度下降更不明显,相对分子质量下降更强烈,表面破坏更严重,老化作用更剧烈.结晶度越高,HDPE缺陷也就越多,在热氧环境中越容易发生氧化,老化现象更严重.%In this article,the influence different degree of crystallinity on the mechanical properties, chemical structure,thermal stability,melting characteristic,average molecular weight and surface morphology evolution of HDPE after xeon photo-oxidation aging were studied by mechanics experiment,attenuated total reflection infrared spectroscopy(ATR-FTIR),thermogravimetry analysis (TGA),differential scanning calorimetry(DSC),gel permeation chromatography(GPC)and scanning electron microscope(SEM),respectively. The results show that higher degree of crystallinity in the HDPE results in a faster decrease in the bending strength,bending modulus and impact strength. The degree of unsaturation,carbonyl index and hydroxyl index increase significantly and the chain branching and chain breaking are more obviously and mainly concentrated in the early part of aging. The thermogravimetry analysis characteristic temperature decreases faster,but the melting peak temperature and the oxidation induction temperature decrease less significantly. The average molecular weight decreases more intensely and the aging degree of surface microstructure is more severe. The higher crystallinity the more the flaws in HDPE,which facilitates oxidation under thermo-oxidation environment and the aging phenomenon is more severe.
展开▼
