Preparation of PU/SiO2 composite shell microencapsulated phase change materials with high thermal stability and thermal conductivity

Abstract

To address the issues of poor thermal stability and thermal conductivity in polyurethane (PU) shell microencapsulated phase change materials (MEPCMs), this study prepared PU/SiO₂-MEPCMs using an interfacial polymerization method combined with electrostatic self-assembly technology. First, the PU shell was synthesized via an interfacial polymerization reaction between isophorone diisocyanate (IPDI) and triethanolamine (TEA). Subsequently, the hydrolyzed product of tetraethyl orthosilicate (TEOS), monosilicic acid (Si (OH)₄), was adsorbed onto the PU shell surface using electrostatic self-assembly technology and reacted with the –NCO groups to form an SiO₂ shell. The effects of the PU/SiO₂ composite shell on the surface morphology, chemical structure, compactness, thermal stability, phase transition performance, thermal conductivity, and thermal cycling stability of MEPCMs were investigated. The results showed that the formation of the PU/SiO₂ composite shell significantly improved the thermal stability, compactness, thermal conductivity, and cyclic stability of MEPCMs. After continuous treatment at 150°C for 120 min, the leakage rate of the core material decreased from 12.13 % to 3.74 %, and the heat-resistant temperature (T_95 %) increased by 30°C. Even after 1000 thermal cycles, MEPCMs still exhibited excellent heat storage performance. Additionally, even under high temperature conditions of 257°C (where pure butyl stearate completely decomposes), the PU/SiO₂-MEPCMs still maintained a stable core-shell structure. The introduction of the SiO₂ shell greatly enhanced the thermal conductivity of MEPCMs, aligning the phase change temperature more closely with that of the core material and effectively reducing the supercooling phenomenon. Furthermore, the stable energy storage system formed by MEPCMs on the finished fabric surface can endow it with excellent temperature regulation functionality.