Effects of Oil-impregnation on Structure and Property of Surface-Roughened BOPP Films
In this study,the structure and properties of two surface-roughened films of biaxially oriented polypropylene(BOPP)before and after oil immersion were investigated.The roughening morphology of BOPP was characterized by optical microscopy,the crystal structure and crystallographic behavior were inspected by DSC and WAXD,and the orientation structure was evaluated by polarized infrared technology.The tensile mechanics,thermal oxidation stability and breakdown strength of the films were tested.The results show that the crystal structure of BOPP films prepared by two kinds of polypropylene with different chain characteristics does not change significantly before and after oil immersion.The orientation parameters θj and fj suggest that the orientation of the amorphous chains is decreased by oil immersion.In addition,the oil immersion improved the breakdown strength of the film.For example,the breakdown strengths of the high tacticity and narrow distribution films are 737 V/μm(before oil immersion)and 863 V/μm(after oil immersion).These results indicate that soaking in the insulating oil medium for a long time,the orientation relaxation in the amorphous region can eliminate the structural defects caused by internal stress and increase the breakdown strength of BOPP films.
Surface-roughened film for capacitorCrystallizationOrientationAmorphous phaseBreakdown strength
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