Experimental Study On The Thermal Conductivity And Mechanical Properties Of Carbon Nanotube/EPDM Rubber

In recent years, the thermally conductive silicone rubber has been studied extensively and certain results have been achieved. However, with the rapid development of modem science and technology, the diversity of different kinds of thermal conductive rubber has also put forward higher requirements.EPDM has not only excellent performance of chemical resistance, electrical insulation, but also lower price than silicone rubber and has greater tensile strength, so it is more attractive to be researched. Since carbon nanotubes (CNTs) first observed in1991, their excellent thermal conductive, mechanical and other properties have been the focus of entire carbon sector.This subject chose CNTs as thermal conductive filler, which were added into EPDM rubber in order to improve the thermal conductivity and mechanical properties of the rubber composites. And CNTs were modified by phenolic resin so as to obtain thermal conductive rubber material with excellent comprehensive performance. Finally, two different kinds of coupling agents were filled into composite materials with different proportions, and the role of coupling agent for improving material thermal conductivity and mechanical properties were researched.The study showed that with the increase of CNTs, the thermal conductivities of carbon nanotubes/EPDM composites showed upward trend; the tensile strength and elongation at break of composites showed the trend of first increased and then decreased, elongation and tear strength were increased. In low-filler content, the large diameter filler was easier to form thermally conductive chain and better integration with rubber matrix than the small one, brittle fracture was not easy to happen. When filler content exceeded a certain value, that was20g, the advantage of small diameter filler showed out and thermal conductivity of composites were higher. In high-filler content, because of thermal conductive filler cannot be effective coated by rubber, the binding ability between filler and EPDM was reduced, resulting in the decline of tensile strength of the material.After modification by coating process, with the modification ratio improved, surfaces of CNTs were coated with large amounts of phenolic resin, active group and roughness of CNTs were increased, surface potential decreased, agglomeration effect of CNTs were reduced, they were more accessible to each other to form thermally conductive chain, the dispersion of CNTs and the ability of combined with rubber matrix were improved. The thermal conductivity and mechanical properties of composite materials filled with modified-CNTs had larger improvement than the ones filled with non-modified CNTs.After coupling agent KH590was added into the composites, the binding ability between CNTs and rubber was effectively improved, interfacial thermal resistance was reduced, thermal conductivity and mechanical properties of composites were improved, when the amount was10%, the effect was significantly better. However, Si-69was not very effective in improving the binding of CNTs with rubber interface.