Abstract: In this work， simultaneous biaxial drawing and sequential biaxial drawing were chosen as two stretching modes to adjust the thickness， extended chain crystal content， fibrillar morphology， and orientation texture of BOPP films， and the working rules of these structural issues on their electrical insulating properties were investigated. The results indicated that a thick lamellar structure with a good thermal stability and an isotropous fibrillated network facilitated an improvement in the breakdown strength and a reduction in the dielectric loss. These results are advantageous to a good understanding on the processing-structure-property relation of polymer film dielectric.

Key words: biaxially stretched polypropylene, extended chain crystal, fibrillated network, breakdown strength