Thermal conductivity of high polymers

Abstract

SJ'nopsiSThe thermal conductivities of linear high polymers were studied experimentally and theoret.ically. A theory of thermal conductivity in linear amorphous high polymers waa derived based on a simple model of molecular structure. Predictions on the effects of molecular weight and molecular orientation on thermal conductivity taken from the theory agree with available experimental data. New data on the thermal conductivity of linear polyethylene and some polyethylene-wax blends are presented. Temperature dependence of the thermal conductivity in polyethylene was analyzed by the per cent crystallinity concept to obtain results which are in accord with the phonon theory of thermal conductivity in dielectric crystals.

Thermal Conductivity of Cross-linked Polymers

“…(1) Thermal conductivity increases with increasing degree of cross-linking. (2) The slope of the curves in Figures 9 and 10 becomes progressively greater as temperature increases.…”

“…When a thermal gradient exists in the polymer, the over-all thermal resistance of the polymer is believed to result from the separate contributions, R1 and R2, of the polymer segments vertical and parallel to the direction of the thermal gradient. Then R, the over-all thermal resistance, is given by ( 1 ) As has been discussed in a previous paper, 8 only R1 will be altered by introducing cross-links into the polymer. However, in the direction of the thermal gradient one-half of the value of the cross-linking parameter X=Mg/Mc should be accounted for, where Mg is the molecular weight of a chain unit and Mc is that of the chain segments between cross-links.…”

3-dimensional anisotropic thermal transport in microscale poly(3-hexylthiophene) thin films

“…Study of anisotropy has already been conducted on numerous polymers. Models by Henning [18] and Hansen [19] were proposed to account for the impact of molecule orientation on the thermal transport in amorphous polymers. For semicrystalline polymers, the molecular alignment can result in larger anisotropy than that in fullyamorphous polymers.…”

A network theory for the thermal conductivity of an amorphous polymeric material

“…Since the changes in the thermal conductivity reported in these references are large enough to have a significant influence on the flow of a melt, it is important to construct a theory which describes the relationship between the history of deformation of a material and the thermal conductivity tensor. Existing theories of thermal conductivity in polymeric materials [7,8] use the idea that energy is transported more readily along the backbone of the molecules than across it, from one molecule to another. The reason for this is that the interactions between two molecules are governed by the relatively weak van der Waals interactions, whereas the interactions between adjacent segments of the same molecule are governed by the strong chemical bonds.…”