Developing energy-efficient cool roof coatings using microencapsulated eutectic phase-change material and poly(methyl methacrylate-co-methacrylic acid) copolymer shell emulsion

Abstract

ABSTRACT The rise in the construction of modern structures of buildings has increased the demand for energy sources to cool indoor and outdoor temperatures. Cool coating is a highly effective roofing technology for absorbing less heat and reflecting more sunlight than conventional coating. These coatings are made from a special type of material with high solar reflectance, allowing them to reflect more sunlight. The cool coating is applied over the building roofs, which gives an efficient way to cool the building inside passively and the surrounding environment. In this context, incorporating phase-change material (PCM) into cool coating enhances its capacity for regulating temperature by storing and releasing heat as required. Combining these two would improve the coating’s overall cooling capabilities, increasing its efficacy in maintaining a lower surface temperature and lowering the cooling energy consumption in buildings. There is a lack of research studies incorporating PCM into a cool roof coating. The present work fills this gap. In this study, we have developed an easy-to-maintain thermal storage cool roof coating using microencapsulated phase-change material (MPCM) latex and white cement. This coating integrates a cooling effect, making it ideal for building applications. Lauric acid (LA), palmitic acid (PA), and stearic acid (SA) eutectic PCM as core were microencapsulated with polymethyl methacrylate-co-methacrylic acid (PMMA-co-MAA) shell using oil-in-water emulsion polymerization. The microcapsule was prepared by altering the core-to-shell ratio. The microcapsules were characterized using various techniques such as thermogravimetric analysis (TGA), polarized optical microscopy (POM), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). The melting temperature of LA-PA-SA eutectic PCM, MPCM 1, and MPCM 2 was 32.66°C, 31.47°C, and 32.73°C, respectively. The TGA analysis indicates that the prepared microcapsules have good thermal stability and degrade in two steps. Microcapsules’ average particle size diameter was observed in the 3–9 µm range. The cool roof coating was fabricated by partially replacing the acrylic copolymer latex with prepared MPCM 1 latex. This study evaluates the influence of MPCM 1 latex loading on the coating’s mechanical and thermal properties. The temperature changes from the building’s exterior to the interior have been recorded using thermal energy transfer analysis. General coating properties such as water resistance, stain resistance, alkali resistance, and gloss were investigated. DSC result shows that the thermal storage enthalpy of the coating has been improved from 17.85 J/g to 37.45 J/g by partially replacing MPCM 1 latex with acrylic copolymer from 50 to 70 wt.%. Coating with 70 wt.% MPCM 1 latex reduced the rise in the room’s temperature, showing it to be a promising candidate for utilizing thermal energy within building technologies.