Measurement of thermal conductivity of polymers using an improved Lee's Disc apparatus

Abstract

An improved Lee's Disc apparatus was designed and utilised to measure the thermal conductivity of various commercial polymers such as low-density polyethylene, polystyrene, polypropylene and poly(ether ether ketone) over a wide range of test temperatures from 40 to 400 °C. The measurements were carried out under vacuum such that convective heat losses were minimised. It was found that the thermal conductivity of semi-crystalline polymers, below melting temperature ( T m ), was dependent on their density and degree of crystallinity and, above T m , on the chain mobility and degradation effects. The thermal conductivity of the amorphous polymer was dependent on mobility of polymer chains below the glass transition temperature ( T g ) and on the density above T g The effect of density, degree of crystallinity and heating/cooling were also separately investigated and found to influence the thermal conductivity of the polymers used.