Thermal aging on ethylene-propylene-diene rubber composites reinforced by samarium oxide, samarium borate and Sb in Sb doped SnO₂

Ethylene-propylene-diene monomer (EPDM) rubber composites reinforced with 50 phr samarium oxide (Sm₂O₃), samarium borate (SmBO ₃) and Sb in antimony doped tin oxide (ATO) are aged at 150°C for different intervals. It is found that neutral Sm₂O₃ and alkaline SmBO₃ can retard the oxidative degradation of EPDM by blocking radical passage. The acidic ATO particles can accelerate the oxidative degradation of EPDM. The trend of tensile strength of EPDM composites is consistent with that of cross-link density of EPDM composites. SmBO₃ and ATO can retard the increase of dielectric loss until 10 days of aging, while Sm₂O₃ can keep the dielectric loss at low level until 14 days of aging. The increased surface charge of filler can make surface and volume resistivity decrease sharply. Antimony doped tin oxide can deteriorate the dielectric strength of EPDM, while SmBO₃ and Sm₂O ₃ can keep the dielectric strength of EPDM at a constant level.