Determination of Thermal Conductivity of Closed-Cell Insulation Materials That Depend on Temperature and Density

Abstract

The main purpose of temperature insulation is to increase the thermal transport resistance of structural materials. The products used for thermal insulation are usually classified as either open cell or closed cell. Expanded polystyrene (EPS), extruded polystyrene (XPS), expanded nitrile rubber (ENR), polyurethane (PUR), polyethylene (PE) and ethylene vinyl acetate (EVA) are examples of some basic closed-cell insulation materials. Thermal conductivity varies depending on density, pore structure and dimensions, as well as the moisture content and temperature of a material. According to the American Society for Testing and Materials ASTM-C518 standard, thermal conductivity is only given for a temperature value of 10 °C. However, climate conditions, environmental temperature and moisture values vary over the course of the day. Therefore, it is important to determine the thermal conductivity of insulation materials that depend on temperature for different climate conditions. In this study, k values of EPS, XPS, ENR, PUR and EVA insulation materials are measured depending on the temperature and density by using heat flow meter methods according to EN 12664, 12667 and ASTM C518 standards. Experimental measurements are taken for temperatures ranging between −10 and −50 °C. From the results, it is observed that k values increase when the temperature increases and decrease when the density increases, for all insulation materials measured. Also, the most rapid change of the k value varying with density is seen with EPS-8.9 (kg/m3) material, while the most rapid change of the k value varying with temperature occurs with PE-35 (kg/m3) material. In contrast, the least deviation of the k value from the nominal value occurs for EVA-60.