The thermal conductivity of polytetrafluoroethylene (PTFE) was studied using an instrumented thermal conductivity apparatus (Lees' disk) and by DSC. The former method was used to study the effect of incorporating fillers into a PTFE/ glass fiber fabric used for conveyor belts in food processing. The effect of crystallinity on thermal conductivity was investigated and different methods of crystallinity determination were compared. The incorporation of aluminum flakes improved heat transport through the composites. The thermal conductivity of PTFE with different levels of crystallinity was measured at 232 degreesC and shown to increase linearly with this parameter.