Therma conductivity of open-cell polyolefin foams

The thermal conductivity and the cellular structure of novel open-cell polyolefin foams produced by compression molding and based on blends of an ethylene-vinyl acetate copolymer (EVA) and a low-density polyethylene (LDPE) have been studied in the temperature range between 24 and 50 degrees C. The experimental results have shown that the cellular structure of the analyzed materials has interconnected cells because of the presence of large and small holes in the cell walls, this structure being clearly different to the typical structure of open-cell polyurethane foams. It has been found that at low temperatures the materials have a slightly higher thermal conductivity than closed-cell polyolefin foams of similar densities. The different mechanisms of heat flow, conduction, convection, and radiation have been analyzed by using experimental measurements and a theoretical model. It has been proved that, in spite of having an open-cell structure, the convention mechanism is negligible, being the radiation mechanism the one which made different the conductivity of materials with varying cellular structures. (C) 2007 Wiley Periodicals, Inc.