Effect of spherulites on water-tree in polypropylene

Polyethylene and polypropylene, crystalline insulating materials, have good insulating properties and workability; therefore, these materials are frequently used as insulating materials in various high-voltage equipment. When crystalline polymer materials are cooled from the melted state, spherulites develop during the cooling process. It is known that these spherulites are in some way related to treeing deterioration which leads to insulation breakdown phenomena in specimens. In this paper, a system to clarify the relationship between water trees degradation and spherulites