Effect of Elastomer Type on Electrical Treeing Behavior of Polypropylene/Elastomer Blends

Abstract

As a thermoplastic material, polypropylene (PP) has been considered as an alternation to cross-linked polyethylene (XLPE) used as cable insulation material due to its high breakdown strength and recyclable nature. A variety of elastomers have been added to the PP polymer to overcome the disadvantages of large elastic modulus, and thereby obtaining acceptable mechanical properties. Electrical treeing is an important factor for ageing of cable insulation, which possibly leads to cable insulation failure. Accordingly, from the viewpoint of safety, it is essential to investigate the ageing behavior in PP material. In this work, two types of elastomers, i.e. polyolefin elastomer (POE) and propylene-based elastomer (PBE), have been blended into isotactic polypropylene (i-PP) to modify its toughness. Effect of the elastomer type on electrical treeing behaviors of the blends has been estimated. It was found that with the increase of the elastomer content from 0 wt% to 30 wt%, the growth rate of electric tree was significantly enhanced and the breakdown time was evidently shortened. As compared with the PP/POE blends, the PP/PBE blends showed higher resistance to electrical tree, especially, at low content of the elastomer at 10 wt%.