Energy-Efficient Insulating Geopolymer Foams with the Addition of Phase Change Materials

This study assessed the impact of the addition of phase change materials (PCMs) under the trade name Micronal 28S on the properties of the manufactured geopolymer foams. Micronal 28S is used as a functional component in foams (insulation materials), foamed building materials, and materials for temperature regulation to improve thermal comfort and indoor climate. The melting point of Micronal 28S is 28 ± 2 °C, and the heat of fusion is ∼140 J/g. As part of the research, geopolymer mixtures containing PCMs in the form of a slurry were prepared in shares of 0, 5, 10, and 15 wt %. Geopolymers were produced based on fly ash. The foaming process was carried out using hydrogen peroxide (H2O2). Physical, mechanical, and thermal properties and analysis of the microscopic microstructure were evaluated. The introduction of Micronal 28S into the geopolymer matrix is conducive to obtaining ultralight foams with a density of about 200 kg/m3. As the share of the PCM increases, the thermal insulating properties of the samples increase by reaching a thermal conductivity coefficient λ of 0.057 W/m*K. Simultaneously, the specific heat increases up to 1.105 kJ/kg*K. Microstructure analysis confirmed that Micronal 28S tends to agglomerate and decrease pore size. The phase change material reduces the mechanical properties of the geopolymers. However, according to the EN 998-1 standard, the conditions for the requirements to be realized by insulating materials used in construction were met by a reference sample and one containing 5 wt % of Micronal 28S. The content in this publication addresses issues in both materials science and mechanical engineering. Although other authors have conducted research using various phase change materials, this work is the first to use PCMs with the trade name Micronal 28S to produce geopolymer foams with excellent thermal insulation properties.