Thermal insulation is very
 important issue in many industrial applications and different materials are
 preferred to satisfy the thermal insulation depending on the applications. One
 of the most important properties of the thermal insulation materials is low
 thermal conductivity. In addition, the cost of the material is another
 important factor. Among the thermal insulation materials, rigid polyurethane
 foams are used in automotive, transportation and building sectors due to lower
 thermal conductivity. Although the thermal conductivity of the rigid
 polyurethane foam is lower than those of many other thermal insulation
 materials, other thermal insulation materials may be preferred in some
 applications due to their lower costs. Therefore, different natural inorganic
 minerals have been added as fillers into the foams, mainly to reduce raw
 materials costs. In this study, kaolin, which is a cheap natural inorganic
 mineral, was incorporated into rigid polyurethane foams in 5, 10 and 15 % in
 mass. Effects of kaolin addition on thermal decomposition and thermal
 conductivity of rigid polyurethane foams were investigated. The results
 revealed that the incorporations of kaolin into the foams slightly increased
 the thermal conductivities of the foams. However, it was found that kaolin
 addition enhanced the thermal stability of rigid polyurethane foams.