Enhancement of thermal conductivity and mechanical properties of silicone rubber composites by using acrylate grafted siloxane copolymers

Thermally conductive composites have attracted much attention due to their application in the thermal management of electronics. But most of the thermally conductive composites exhibit poor filler dispersion and weak filler-polymer interfacial interaction, which would deteriorate the mechanical properties and impede the enhancement of thermal conductivity. Herein, three new copolymers were synthesized through hydrosilylation reaction of poly(dimethylsiloxane-co-methylhydrosiloxane) (PDMS-PHMS) with methyl methacrylate (MMA), glycidyl methacrylate (GMA), and 3-(trimethoxysilyl)propyl methacrylate (MPS), respectively. The copolymers were used to enhance the thermal conductivity and mechanical properties of Al2O3/silicone rubber (SR) composites. MPS grafted PDMS-PHMS and GMA grafted PDMS-PHMS could increase the bound rubber content of Al2O3/SR compounds, and increase the crosslink density and filler-rubber interaction of Al2O3/SR vulcanizates. The addition of MPS grafted PDMS-PHMS into an Al2O3/SR (500/100) composite could increase the tensile strength and elongation at break from 1.72 MPa and 33.0% to 3.69 MPa and 56.9%, respectively, and increase the thermal conductivity from 1.42 to 1.73 W/(m·K). The MPS grafted PDMS-PHMS/Al2O3/SR composite was successfully used as a thermal interface material between a LED chip and a heat sink, showing outstanding thermal management capability as a thermally conductive composite.