Analysis of Electrothermal Stress Aging Characteristics of Polypropylene Based on Molecular Dynamics
For polypropylene(PP)film capacitor,which is used widely in high-voltage direct current(HVDC)engineering,its internal high temperature and high field strength are the main causes of PP aging.Based on simulation method of dynamics,the aging process of PP under electrothermal stress is analyzed at molecular level.Firstly,molecular models of PP and PP containing carbonyl groups are set up.Based on the reaction force field,the pyrolysis reaction of PP under thermal and electrical stress is simulated and the main product formation process is analyzed;Then,based on the COMPASS force field,the variation of mechanical and insulation performance of PP under thermal stress is analyzed.The results show that the C—H bond firstly breaks during the PP cracking reaction,followed by the C—C bond breaking and the formation of carbonyl groups.During this process,thermal stress has a more significant effect on the electrothermal aging of PP;When the temperature is below 450 K,the mechanical parameters of PP remain basically unchanged.While,when the temperature reaches 600 K,the mechanical parameters of PP change significantly and the stability decreases;Carbonyl groups affect variation of mechanical and insulation properties of PP during aging.The energy gap of PP containing carbonyl groups decreases by 28.21%,and the elastic modulus increases by 15.3%,32.85%,and 27.08%at 300 K,450 K,and 600 K,respectively.
polypropyleneinsulation performancemolecular dynamicsCOMPASS force fieldreaction force fieldaging
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维普
