Dielectric Properties of Polypropylene Film for Capacitor Based on Irradiation Crosslinking Modification
The traditional polypropylene(PP)film has the problems of low breakdown field strength and high conduc-tivity loss under high temperature and strong electric field environment.We proposed a new modified method based on γ-ray irradiation for polypropylene film,and studied the effects of irradiation dose and sensitizer on the dielectric proper-ties of polypropylene films.Polypropylene films containing sensitizers such as trimethylolpropane triacrylate(TMPTA)and pentaerythritol triacrylate(PETA)were prepared.Total irradiation dose of 0,5 and 10 kGy were carried out under 60Co-γ-ray source.The molecular chain and aggregation structure of irradiated cross-linked polypropylene film were ana-lyzed,and the influences of cross-linked structure on the conductivity and breakdown field strength of polypropylene film under high temperature and strong field were studied.The results show that high energy radiation can form a three-dimensional network structure in the polypropylene film,enhance the force between molecular chains and thermal stability,effectively inhibit the carrier transport in polypropylene,and significantly improve the high-temperature dielec-tric properties of polypropylene film.At 115℃,the conductivity of the modified polypropylene film with the crosslinking degree of 25.04%is decreased by 64.2%,the breakdown field strength is increased by 16.6%,and the maximum theoreti-cal energy storage density reaches 3.78 J/cm3.It is revealed that irradiation crosslinking modification can effectively improve the high temperature dielectric properties of polypropylene films.
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