热老化对恒定内压下PE管材性能的影响

为了研究热老化对恒定内压作用下的PE管材结构和性能的影响,在80℃水浴环境中对聚乙烯管进行了长期压力测试,通过力学性能测试、热重试验、DSC测试以及衰弱全发射红外光谱试验,分析了老化过程中管材的结构和性能变化。结果表明,在老化过程中,随着老化时间的增加,PE管材抗氧化剂逐渐被消耗,2200h时,老化管材的氧化诱导期降低至原始管材的73.1%;随着老化时间的延长,管材表面发生氧化,产生了談基(-C=O)与務基(-OH)等含氧基团。热老化使PE分子链发生了以交联为主的化学反应,导致管材的热稳定性上升。结晶度增加、分子链交联以及管材表层氧化等,导致拉伸强度略有提升,而管材的断裂伸长率和冲击强度分别下降了27.5%.28.9%。

Effect of Thermal Ageing on Properties of PE Pipes under Constant Internal Pressure

In order to study the effect of thermal ageing on the structure and properties of PE pipes under constant internal pressure, a long-term pressure test was carried out on the PE pipe at 80℃ water bath. The physical property and chemical structure before and after ageing were determined by mechanical properties test, thermogravimetric test, DSC test and attenuated total reflectance-Fourier transform infrared spectrum test ( ATR/FTIR ). In the ageing process, the antioxidants were gradually consumed with the increase of ageing time, and the oxidation induction time of the aged pipes was reduced to 73.1 % until 2200 h. The ATR/FTIR further showed that the crystallinity of PE increased. The surface of the pipe was oxidized and produced oxygen groups, such as carbonyl group (-C=0) and hydroxyl group (-OH ). The thermal ageing mainly caused crosslinking among the molecular chains, which increased the thermal stability of the material. The increase in crystallinity, cross-linking of molecular chains, even the oxidation of the surface layer caused the slight increase in tensile strength, while elongation at break and impact strength decreased by 27.5% and 28.9%, respectively.