Crosslinked Waterborne Polyurethane Solid–Solid Phase Change Materials with Polyethylene Glycol for Thermoregulating Textiles

Solid–solid phase change materials integrate high heat storage, leak-proof performance, and dimensional stability, thereby positioning them as optimal candidates for thermoregulating textile applications. This study effectively synthesized PEG-based crosslinked waterborne polyurethane phase change materials (WPU-SSPCMs) with polyethylene glycol (PEG) as the soft segment, hexamethylene diisocyanate (HMDI) as the diisocyanate, and glycerol (GL) as the multifunctional chain extender. The effects of PEG molecular weight, diisocyanate type, chain-extension temperature, and monomer molar ratio on the phase transition behavior and thermal stability of WPU-SSPCMs were systematically investigated. The results indicate that at a PEG molecular weight of 2000, a chain-extension temperature of 70 °C, and a monomer molar ratio of n(PEG:HMDI:GL) = 1:2:0.67, the synthesized WPU-SSPCMs exhibited optimal comprehensive performance. The material demonstrated a melting temperature of 33.38 °C with a high enthalpy of 80.31 J/g. It displayed characteristic solid–solid phase transition behavior without evidence of liquid leakage during heating. Following 100 thermal cycles, the enthalpy variation remained below 1 J/g, indicating exceptional thermal and cycling stability. When applied to cotton fabric, the resultant thermoregulating textile displayed a buffering plateau during both heating and cooling processes, demonstrating a pronounced temperature-regulating effect relative to untreated fabric. The developed WPU-SSPCM holds considerable promise for applications in intelligent temperature regulation.