Crazing of glassy polymers in oil-impregnated cables
- 31 October 2016
- conference paper
- Published by Institute of Electrical and Electronics Engineers (IEEE)
Abstract
The need for lower dielectric losses in EHV cables has stimulated recent interest in the use of oil-impregnated polymer films in place of paper. To minimize swelling by the oil and resultant degradation of mechanical and electrical properties, polymers with relatively high glass transition temperatures such as polyphenylene oxide, polydian carbonate, and polysulphone have received most attention.1,2 Such glassy materials under a mechanical strain like that which may be induced in a cable either in wrapping the film or in bending the finished cable may develop small crazes or cracks particularly in the presence of oils. In this paper we have examined the tendency of glassy polymers to craze and swell in a number of commonly used cable oils as well as in a number of pure alkanes including the molecular weight range found in these oils. Measurements of dry crazing have also been made as a function of temperature and the influences of annealing and molecular orientation investigated. The results suggest a theory relating crazing to the glass transition temperature which permits quantitative predictions of both dry and solvent crazing.Keywords
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