|MadSci Network: Engineering|
In order to conduct electricity effectively, a substance needs to have free electrons or ions. To conduct heat well, it needs free mobile molecules, electrons, or ions to transfer kinetic energy, i.e., heat, from one part of the substance to another by mass transfer. Polymers are not typically any worse conductors of heat or electricity than other non-metallic solids - though we think of rubber as the insulator of all insulators, solids such as quartz are even more insulating. Indeed, some polymers have structures that allow electrons to flow from one end of a molecule to another, making them much better electrical conductors than typical ionic or covalent solids. The very low thermal and electrical conductivity associated with polymer foams is due to the fact that they are mostly air, which is a very poor conductor indeed! The role of the polymer here is simply that only such large molecules can sustain the rigid foam structure.
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