Interfacial properties of XLPE/EPDM laminates

Interfacial properties such as space charge accumulation and breakdown char acteristics in crosslinked polyethylene (XLPE)/ethylene propylene diene ter polymer (EPDM) laminates were investigated. Homocharge is observed in EPDM containing 1,4-hexadiene while heterocharge is observed in EPDM containing 5-ethylene-2-norbornene. Interfacial charge develops when the EPDM is lamin ated with XLPE. The polarity of this interfacial charge reverses at less th an a few tens of hours heat treatment at 80 degrees C. de breakdown voltage shows a sequential change of an increase, a decrease and a slight increase as a function of heat treatment time, which holds true for both interfacia l and volume breakdown voltages. A maximum breakdown voltage is observed at 20 to 24 h heat treatment. After long heat treatment, silicone grease used in the interface shows lower interfacial breakdown voltage than silicone o il for the de case, which was attributed to the additives in the grease and the molecular weight of silicone molecules in oil and grease. Details of t he results are given and their origins discussed.