Morphology and electrical breakdown properties of LDPE-polypropylene copolymer blends

In this study, the specimens of low-density polyethylene (LDPE) and blend p olymers of LDPE and a random copolymer of ethylene and propylene were prepa red by the blowing process and T-die method. The differences in electrical breakdown properties and morphology between the specimens made by the two d ifferent methods were studied. It was found that the specimen made by the T -die method had a higher electrical breakdown strength than the specimen ma de by the blowing process, except for the DC breakdown strength in some cas es at 30 degreesC. The morphology of the specimens was investigated by mean s of the measurements of thermal shrinkage, infrared dichroism, and X-ray d iffraction. The specimen made by the T-die method has a stronger orientatio n in both the crystalline and amorphous phases than the specimen made by th e blowing process. The difference in morphology is supposed to be correlate d with the difference in electrical breakdown properties between the specim ens made by the two different methods. It was concluded that the electrical breakdown properties are strongly affected by the orientation of chains in the specimen. (C) 2001 John Wiley & Sons, Inc.