Influence of Thermal-stress Aging on Insulation Performance of BOPP Film for Capacitor
For studying the influence of thermal-stress aging on dielectric performance of polypropylene film(biaxially oriented polypropylene,BOPP)for capacitor,the BOPP film with a thickness of 7.8 μm for capacitor is streteched down at 120℃and is subjected to aging treatment at the stresses at 0,10,20 and 40 N respectively for 168 hours.The tensile stress-strain characteristics of it is tested by the universal material testing machine.Such electrical characteristics as electrical conductivity,dielectric constant and DC breakdown of the sample are tested at 85℃.The influence of the thermal-stress aging on the trap characteristics of BOPP film is analyzed by thermally stimulated depolarization current(TSDC)technique.The results show that the thermal-stress gaing leads to significant increase of the electrical conductivity of BOPP films.Also,the termal action leads to reduction of dielectric constant and the the unidirectional stress causes the dielectric constant to increase.In addition,the TSDC test results show that the thermal-stress aging significantly increases the trap density and trap energy levels in BOPP film.The above-mentioned result shows that the thermal-stress aging leads to reduction of electrical performance of BOPP film,of which more attention and research shall be strengthed.
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