Heat Conductivity of Rubber

[lpgman]

I'm casting an electrical heating element in rubber and want to increase the heat conductivity of hard rubber. Are there proven methods for putting additives in rubber that will increase its conductivity? What are those additives and what will be the heat conductivity of the rubber with the additives? What effect will the additives have on electrical conductivity?

 

[40WattBulb]

Have you considered filling the rubber with aluminium flake.