Polyurethane foams reinforced with microspheres - assessment of the application in construction as a thermal insulation material

Abstract

In the paper, the authors presented a polyurethane material with the addition of microspheres derived from coal fly ash. The filler addition ranged from 5 to 20%. The manuscript included studies such as morphology, density, thermal conductivity, basic mechanical analyses and an extensive flammability analysis. The aim of conducting the above studies was to confirm the feasibility of replacing commercial rigid polyurethane foam (RPUF) in construction with a material modified with microspheres. The above studies were preceded by an analysis of the filler, which was characterized by spherical particle shapes, a moisture content of 0.16% and a loss on ignition of 0.84%. The microspheres consisted mainly of silicon and aluminium oxides. The addition of microspheres improves the mechanical properties of polyurethane composites-modulus of elasticity and hardness. However, brittleness deteriorated. The addition of microspheres up to 15 wt.% does not adversely affect the thermal conductivity of the polyurethane-microspheres (PU-M) composite. Flammability tests have shown that the addition of microspheres delays the ignition of the samples; more oxygen is needed to start the material burning. Unfortunately, the filler results in more smoke produced. On the basis of thermogravimetry, a two-stage nature of foam degradation was observed, which is typical for this group of materials. As the amount of microspheres in the foam increased, the residue at 700 °C increased. As a result of the analyses carried out, it was concluded that the addition of microspheres to polyurethane foam could be successfully applied without any deterioration in the properties of the material and that some properties, such as mechanical properties, were improved.