Effects of silicon carbide as a heat conductive filler in butyl rubber for bladder tire curing applications

Rubber composites are widely used in tires and their related applications. In the present study, butyl rubber/carbon black/silicon carbide (α-SiC) composites were prepared by melt blending. They are used in tire curing applications for utilization of silicon carbide for the development of heat conductive bladder. The effect of α-SiC micro particle loading on resin curing characteristics, tensile properties (normal and aged), hardness, tear strength and morphology were studies. We also investigated its effect on the thermal transport properties of carbon black filled butyl rubber such as its heat conductivity, heat diffusivity, and specific heat capacity. A heat transfer mathematical modeling and computer simulation were conducted using ABAQUS finite element software to simulate the effect of bladder composite heat diffusivity increment on temperature-time dependency for different points of a tire during curing process. The results showed an average increase of 72% in the thermal conductivity, an average increment of 45% in heat capacity, and an average increment of 13% in heat diffusivity coefficient of carbon black filled composite in the presence of 18 phr (part per hundred of rubber) of α-SiC, without significant loss of mechanical properties. Further addition of α-SiC to 28 phr while decreasing mechanical properties did not have a further improving effect on the composite thermal conductivity and its thermal diffusivity coefficients. The tire curing simulation results revealed that it is possible to reduce the steam pressure inside of curing bladder from 22 to 20 bar (9%) in the presence of 18 phr α-SiC in bladder formula.