Abstract
Microencapsulation of phase change materials (PCMs) could prevent the leakage of PCMs during solid–liquid phase change process. However, their applications are mainly limited by the compactness and thermal stability of the traditional polyurea shell microcapsules. To increase the thermal compactness and thermal stability of PCM microcapsules, tetraethylorthosilicate (TEOS) was employed to form polymer/SiO2 composite shells to enhance the mechanical performance of polyurea and polyurethane microcapsule via interfacial polymerization and in situ polymerization. The morphology and chemical components of the microcapsules were characterized by field-emission scanning electron microscope (FE-SEM) and Fourier transform infrared (FT-IR) spectroscopy, respectively. The thermal properties of the microcapsules were investigated by differential scanning calorimetry (DSC) and thermal gravity analysis (TGA). The results showed the smoothness and compactness of both polyurea–SiO2 and polyurethane–SiO2 microcapsules enhanced slightly, when compared with that without TEOS addition. Moreover, the SiO2 composite shell had good effect on thermal compactness, as the weight loss rate of polyurea–SiO2 microcapsules and polyurethane–SiO2 microcapsules decreased 3.5% and 4.1%, respectively.
Highlights
Traditional MicroPCMs still have some disadvantages of leakage during the solid–liquid phase transition [21,22], which probably results in Polymers 2018, 10, 726; doi:10.3390/polym10070726
polyethylene glycol 400 (PEG 400) has a macromolecule flexible chain, which can improve the flexible and resilient of polymer, while TEOS carry out hydrolysis polymerization to form polyurea–SiO2 or polyurethane–SiO2 composite shell
DETA (4 g) was slowly dropped into the emulsion at a stirring rate of 500 rpm for 2 h with a mechanical agitation, while the temperature of the solution was controlled at 40 ◦ C, the temperature was raised to 70 ◦ C rapidly, and the emulsion was cured under 500 rpm of agitation for 2 h to form a polyurea–polyurethane–SiO2 MicroPCMs slurry
Summary
Due to the rapid growth of the consumption of fossil fuels followed by environmental impact and energy resources [1], both scientific societies and industrial communities are concentrating on the improvement of energy utilization efficiency and the development of renewable energy [2,3,4,5,6,7,8]. During the fabrication of polyurea, MicroPCMs, the toxic cosolvent tetrahydrofuran, acetone, and cyclohexane are usually chosen to form the miscibility of n-alkane PCMs and isocyanate To solve these issues, ethyl palmitate has been used, and avoids the malodor in traditional MicroPCMs. In the end, certain defects exist in the thermal stability and compactness of traditional polyurea MicroPCMs. In the end, certain defects exist in the thermal stability and compactness of traditional polyurea MicroPCMs In this paper, both polyethylene glycol 400 (PEG 400) and tetraethylorthosilicate (TEOS) were selected as functional shell-forming monomers to enhance the thermal stability and compactness of traditional polyurea MicroPCMs. PEG 400 has a macromolecule flexible chain, which can improve the flexible and resilient of polymer, while TEOS carry out hydrolysis polymerization to form polyurea–SiO2 or polyurethane–SiO2 composite shell. It is anticipated that, the compactness and thermal stability would be enhanced via incorporating SiO2 into organic polyurea or polyurethane shell
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