Effect of nanosized carbon black on the morphology, transport, and mechanical properties of rubbery epoxy and silicone composites

Three different types of nanosized carbon black (CB), Printex XE2 (CBP), Vulcan XC72, and Printex 140 U (CBU), were dispersed by mechanical mixing in rubbery epoxy (RE) and silicone to produce composites. It was found that the maximum possible loading of CB in the polymers depended on the surface area of CB. For a given loading, all three CBs produced similar improvements in the thermal conductivity of the resulting composites, but their effects on the electrical conductivity varied and ranged from insulating composites with CBU to conducting composites with CBP. CBP produced a greater improvement in the electrical conductivity than the thermal conductivity of the polymers compared to the other CBs. This was attributed to the high structure of CBP, which led to the formation of a concatenated structure within the matrix. The CB/silicone composites had a similar thermal conductivity to that of the CB/RE composites, but only the CBP/silicone composite produced at 8 wt % loading was electrically conducting. The compression and hardness properties of RE were also significantly improved with the addition of CB. However, in the case of silicone, only CBP had a considerable effect on the compression properties. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012