基于热分解动力学的中密度聚乙烯光氧老化行为分析

摘要

In this article,the artificial accelerated aging test of medium density polyethylene(MDPE) was carried out for 64 days under Xeon environment. The characteristics of thermal stability,chemical structure,mechanical properties and kinetics parameters including the activation energy and pre-exponential factor evolution of MDPE after photo-oxidation aging were studied by thermogravimetric analysis(TG),attenuated total reflection infrared spectroscopy(ATR-FTIR), mechanical test and thermal degradation kinetics methods including Coats-Redfern method and Kissinger method. The degradation behavior and aging mechanism of MDPE were explored. The results showed that during the aging period,the thermal stability decreased and the concentration of carbonyl and hydroxyl groups increased,the rupture of molecular chain was intensified while the bending and impact strength reduced gradually.After 64 days of aging,the bending and impact strength of MDPE declined by 17.4% and 47.3%,respectively.With the increase of aging time,the activation energy of MDPE decreased obviously and dominated in the early stage of aging,at which the aging phenomenon is more significant.%在氙灯光氧环境中对中密度聚乙烯（MDPE）进行了64天的人工加速老化实验，以研究其在光氧环境下的老化行为及规律。本文利用热重分析法（TG）、衰减全反射红外光谱技术（ATR-FTIR）、力学试验和热分解动力学方法分别研究了中密度聚乙烯（MDPE）在光氧老化环境中热稳定性、化学结构、力学强度和包括活化能及指前因子的动力学参数的变化规律，探究了MDPE的老化行为及老化机理。结果表明：随老化时间增加，MDPE热稳定性能下降，分子结构中产生羰基、羟基等含氧基团，分子链断裂，支链增加，弯曲强度和冲击强度下降。老化64天后，弯曲强度和冲击强度分别下降了17.4%和47.3%。采用Coats-Redfern和Kissinger方法均表明MDPE活化能均随着老化时间增加而减小，且老化初期下降更明显，表明初期MDPE老化作用更加剧烈。