The effects of different fly ash fillers on the mechanical properties, thermal and fire behaviors of rigid polyurethane foams

Abstract

Fly ash which is a by-product of coal-fired power stations has been used as filler in different polymeric materials for different purposes. Since the chemical composition and the size of fly ash may vary depending on the coal type and combustion, properties of fly ash should be examined before the incorporation of fly ash into polymeric materials. In this study, two fly ashes which have different chemical compositions are used as filler in rigid polyurethane foams. The fly ashes were added in 5 %, 10 %, 15 % and 20 % in the total mass. The morphology of polyurethane foam cells was observed by using scanning electron microscopy and the effects of two different fly ashes on the thermal conductivity, the compressive strength, thermal stability and flammability of rigid polyurethane foams were investigated. Experimental results indicated that fly ash addition into rigid polyurethane foam has no negative effects on thermal conductivity of the materials; however it caused decreasing in the compression strength within the acceptable limits. In addition, it was determined that the foam materials filled with the fly ash containing high amount of SiO2 shows better fire resistance and thermal stability.