Electrical insulation performance of flame retardant fillers filled with polypropylene/ethylene propylene diene monomer composites

Flame retardant fillers composed of zinc hydroxy stannate (ZHS), calcium borates (CaB), and NP-100 were embedded separately in 50% polypropylene (PP) and 50% ethylene propylene diene monomer (EPDM) blends. Several formulations containing flame retardant fillers, PP, and EPDM were prepared using an internal mixer and were molded in a compression mold to form test samples. The effects of filler loading (15, 30, 45, and 60 vol%) on the dielectric breakdown strength and contact angle were determined. It was found that PP/EPDM/NP-100 has higher breakdown strength than PP/EPDM/ZHS and PP/EPDM/CaB. The contact angle of PP/EPDM/NP-100 and PP/EPDM/ZHS showed an ascending order with filler loading, implying an increase in hydrophobicity. With regard to the PP/EPDM/CaB system, the contact angle showed an ascending order up to 30 vol% followed by a descending order at 45-60 vol%. Water absorption studies indicated that PP/EPDM/NP-100 has lower water absorption compared with PP/EPDM/ZHS and PP/EPDM/CaB. PP/EPDM filled with 15 vol% NP-100 was found to exhibit interesting insulating properties in comparison with other composite systems, thanks to high breakdown voltage, good hydrophobicity, and low water absorption. Copyright (C) 2014 John Wiley & Sons, Ltd.