Reversible thermochromic microencapsulated phase change materials with silane-terminated polyurethane shell

In this study, silane-terminated polyurethane microencapsulated phase change materials (SPU-MPCM) with reversible thermochromic properties were successfully synthesized by in-situ polymerization. The polyurethane prepolymer was prepared from dicyclohexylmethylmethane-4 (HMDI), butane-1,4-diol (BDO) and trimethylolpropane (TMP). Meanwhile, 3-mercaptopropyl trimethoxysilane (KH-590) was selected to modify silane-termination on the polyurethane prepolymer to obtain the shell material. The influence of isocyanate groups on the discoloration properties of the core composite can be avoided obviously by the silane-terminated shell material. SPU-MPCMs were prepared by in-situ polymerization using crystal violet lactone (CVL) as thermochromic colorant, bisphenol AF(BPAF) as color developer, n-butyl stearate (BS) as solvent and polyvinyl alcohol(PVA) as emulsifier. The effects of the amount of emulsifier and core/shell ratio on the surface morphology, particle size distribution and phase change properties of SPU-MPCMs were studied. The SPU-MPCMs prepared in this study have a relatively high latent heat of phase change (Δ H m  = 122.2 J/g, Δ H c  = 125.1 J/g) and can indicate the latent heat absorb-storage-release state through obvious color changes. At the same time, it also presents excellent thermal stability and cycle durability, high energy storage efficiency ( E  = 76.8 %), and thus showing great application potential in wearable electronic devices, smart material coatings and temperature sensitive medical systems.