Closed-cell polyurethane spray foam obtained with novel TiO2–ZnO hybrid fillers – mechanical, insulating properties and microbial purity

Abstract

Much attention is currently being paid to organic-inorganic composite materials and their unique physicochemical and functional properties. In the present work, for the first time, it is investigated how the incorporation of inorganic oxide fillers affects the mechanical and insulating properties and microbial purity of building materials, closed-cell polyurethane spray foam (for insulation and sealing of ceilings and walls: including attics – the inner side of the roof and even the outer walls of buildings). Two types of inorganic oxide fillers, TiO2 and TiO2–ZnO synthesized via a sol-gel method, were used. The physicochemical properties of the fillers were evaluated, including dispersion, morphology, textural and crystalline structure, and chemical composition. The main objective of the research was to evaluate how the addition of fabricated inorganic fillers (in amounts of 1, 2.5, 5 and 10 wt%) affects the functional properties of closed-cell polyurethane spray foam. The results indicate that the incorporation of inorganic oxide fillers into the polyurethane matrix improves the strengthand thermal properties of the foams (even over time). Moreover, materials constructed using closed-cell polyurethane spray foam and inorganic oxide fillers offer good application potential. In particular, the synthesized TiO2–ZnO hybrid system provides the possibility of modulating the PUR (polyurethane) foam structure in terms of the number and size of pores (reduction of the average pore diameter by approximately 20% – compared to the reference sample). Consequently, it can significantly increase the density (32.2–36.3 kg/m3), strength (about 10% compared to the reference sample), structural stability, microbial purity of the material and maintain a high level of insulation (reference sample 0.0222 W/(m.K) and sample with the addition of 5 wt% of TiO2–ZnO – 0.0215 W/(m.K)). The obtained spray foam can be used as innovative insulating construction coatings. The use of such materials will ultimately have an impact on the indoor environmental quality.