Remarkable enhancement of mechanical and dielectric properties of flexible ethylene propylene diene monomer (EPDM)/barium titanate (BaTiO3) dielectric elastomer by chemical modification of particles

In this study, three types of coupling agent, titanium tris(dodecylbenzenesulfonate) isopropoxide (NDZ 109), gamma-methacryloxypropyltrimethoxysilane (KH570) and vinyltrim + ethoxysiloxane homopolymer (SG-Si6490), were utilized to reduce the polar surface energy of barium titanate (BaTiO3) particles from 37.53 mJ m(-2) to 0.77 mJ m(-2), 16.52 mJ m(-2) and 5.46 mJ m(-2), respectively. At 30 vol% filler loading, NDZ 109 treated BaTiO3 with the lowest polar surface tension exhibited a remarkable compatibility with ethylene propylene diene monomer (EPDM) gum shown by the bound rubber content. It is found that just 1% (by weight of BaTiO3 amount) coupling agents SG-Si6490 can raise the tensile strength of EPDM with untreated BaTiO3 composite from 1.94 MPa to 9.00 MPa, due to the C=C bonds from vinyl groups. In terms of electrical properties, when untreated BaTiO3 loading was 30 vol%, the dielectric constant of EPDM control can increase from about 2 to 7. Moreover, the SG-Si6490 treated BaTiO3 further improved the dielectric constant of EPDM with untreated BaTiO3 composite from 7 to around 8. EPDM with NDZ109 treated BaTiO3 composite exhibited the lowest volume resistivity among EPDM composites.