Heterogeneous phase change polyurethane composite foam with gradient thermal insulation for thermal regulation of heat/cold sources

Polyurethane foam is usually one of the key materials to improve the energy efficiency of cold chain logistics and buildings. In order to achieve better thermal insulation effect for cold chain logistics and building thermal insulation system, a series of micron high thermal storage and high thermal conductivity palmitate palmitate (PP) phase change microcapsules (MPCM) with different content of thermal conductive graphite (GP) were synthesized, and heterogeneous phase change polyurethane composite foam (PUF) with high thermal regulation ability was prepared. The effects of different GP content on the morphology, chemical structure, thermal storage performance, thermal stability and thermal conductivity of MPCMs were compared. The foaming performance, mechanical property, thermal insulation performance and mechanism of PUF with different types of MPCMs were discussed. Results show that, the optimal MPCM (MC-3) exhibits a high molten enthalpy of 200.67 J/g. After 300 heating-cooling cycles, the leakage rate is only 2.54 %. Compared with pure PP MPCM, 1.5 wt% GP can increase the thermal conductivity of MC-3 by 46.54 %. In addition, MC-3 not only effectively improves the thermal insulation performance of PUF, but also retains its good foaming performance. Compared with PUF, the equilibrium temperature at the center of the upper surface of MC-3/PUF on a 100 °C heating plate is only 37 °C, a decrease of 22.92 %. Meanwhile, MC-3/PUF has excellent heat/cold sources insulation performance and produces a distinct temperature gradient distribution. This is expected to provide new ideas for the design and development of high-efficiency thermal insulation foam materials.