Effects of polymer chain orientation upon the thermal conductivity of polymethyl methacrylate at liquid nitrogen temperatures.

Abstract

Measurements of the thermal conductivity of commercial samples of polymethyl methacrylate (Plexiglas) with random and partially oriented polymer chains were made at liquid nitrogen temperatures to provide empirical guidelines into relationships of heat transfer mechanisms of amorphous polymers. Cast samples were formed to have degrees of stretch of one, two, three and four times original length. These samples were found to have thermal conductivities of 1.67, 1.91, 2.05 and 2.10 ± .04 mwatt/cm-˚K respectively. An extruded sample was determined to have an effective degree of stretch of two. Comparison was made with an empirical model based on component thermal conductivities obtained by partitioning with respect to vibrational modes into longitudinal and one- and three- dimensional transverse components.