MadSci Network: Engineering

Re: why are polymers bad heat and electrical conductors in atomic form

Date: Thu Apr 4 19:45:25 2002
Posted By: Chris Fellows, Post-doc/Fellow, Chemistry, University of Sydney
Area of science: Engineering
ID: 1016730451.Eg

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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