Thermally conductive gap pads / gap filler pads that are provided for electronic thermal management have nearly always been fabricated from silicone rubber based materials.
One of our customers in the aerospace electronics industry reported their design required thermal interface pads. However, the pads had to resist the effects of coolants and fuels, which tend to severely swell and degrade silicone rubber based materials. The usual silicone based gap pads would break down and likely contaminate the system.
Stockwell Elastomerics suggested that our customer evaluate a 60 durometer, nickel-graphite filled fluorosilicone material. Nickel-graphite based fluorosilicone rubber is normally used for electrically conductive EMI shielding gaskets that require fluid resistance. However, we had the material tested for thermal properties and learned that our SNEF-60 has a thermal conductivity of 0.5 W/mK. Although the 60 durometer Shore A hardness is firmer than most of our gap pad materials, our customer was able to incorporate enough compression in their hardware design to provide adequate contact on the nickel-graphite filled thermal pads.
Subsequently, we also had our SCF-444, 45 durometer silver plated aluminum filled fluorosilicone tested for thermal properties – and the results were a thermal conductivity of 1.2 W/mK. Saint-Gobain Performance Plastics group performed the thermal testing, even though the material tested was not theirs. Kudos to their technical service group for their assistance!