Improvement of electrical properties and thermal conductivity of ethylene propylene diene monomer (EPDM)/barium titanate (BaTiO₃) by carbon blacks and carbon fibers

The aim of the study was to use carbon fibers and carbon blacks to improve the thermal conductivity, mechanical and dielectric properties of ethylene propylene diene monomer (EPDM)/barium titanate (BaTiO₃) composites. It was found that 7.5 vol% carbon blacks, with high specific surface area, can make complex viscosity of EPDM/BaTiO₃ compound to become non-sensitive to varying shear. Due to the sulfuric atom and C=C groups on surface of carbon blacks, 10 vol% carbon blacks can enhance the tensile strength and tear strength of EPDM/BaTiO₃ (70/30) from 9.00 MPa and 21.06 kN m⁻¹ to 14.32 MPa (59% increase) and 30.02 kN m⁻¹ (43% increase). It was found that the 10 vol% spherical carbon blacks with high specific area can partially contact BaTiO₃ and fill the gap between BaTiO₃ particles to increase thermal conductivity and dielectric constant of EPDM/BaTiO₃(70/30) from 0.323 W m⁻¹ K⁻¹and 7 at 5 MHz to 0.632 W m⁻¹ K⁻¹ (95% increase) and 746 (106 times increase) at 5 MHz, respectively. When the filler content was 10 vol%, carbon blacks and carbon fibers can decrease the volume resistivity of EPDM/BaTiO₃ (70/30) from 2.23 × 10¹³ to 6.37 × 10⁵ Ω m (eight order of magnitude drop) and 4.25 × 10¹¹ Ω m (two order of magnitude drop), respectively.