Interface Traps and Swelling of Polypropylene Films Immersed in Silicone Oils

Biaxially stretched PP (polypropylene) films immersed in silicone oil showed TSC peaks P1 and P2 due to ions trapped in the oil-PP interface region. Their peak temperatures were lowered by oil-PP interaction such as swelling. The equations governing the swelling of a crystalline polymer were deduced from the analogy of the swelling of a cross-linked polymer. The experimental values of the degree of swelling of PP films immersed in silicone oil agreed well with the theoretical ones calculated from the equations. TSC peak temperatures decreased with increasing degree of swelling of PP films. The good correlation between TSC and swelling gave evidence for the modification of surface traps by swelling.