Preparation Of Nano/Microencapsulated Phase Change Materials With Amphiphilic Polyurethane And Their Properties

Recently it became an active research direction to study the latent heat of phase change materials for energy storage and temperature controlling. How to pack the materials effectively is the core problem that hinders the application of the phase change materials. Now, the microencapsulation technology is the main method for the packaging of phase change materials, it can solve the problems such as volume changing and flowing when the phase change between solid and liquid happens.In this paper, we designed and prepared a series of water-borne polyurethane, composed of hydrophilic chain, hydrophobic chain and unsaturated chain, as shell materials. We found that three of them having good emulsifying ability, with their double bonds at the end of the chain,in the main chain and in the branch respectively. Then poly(tetramethylene ether glycol), solid paraffin and methyl stearate were emulsified by the polyurethane prepolymers. After emulsion polymerization, the nano/microencapsulated phase change materials(N/MEPCMs) with cross-linked shell were prepared. The properties of the N/MEPCMs were investigated by Fourier Transform Infrared Spectroscopy (FT-IR), Nuclear Magnetic Resonance(NMR), Dynamic Light Scattering (DLS), Transmission Electron Microscopy (TEM), Differertial Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA) and so on. It was indicated that polyurethane prepolymers had enough tensile strength, hardness and flexibility to sustain core materials, endure the volume changing of phase change. There were two kinds of particle structures with the N/MEPCMs: core-shell structure and complex structure. The particle size became smaller with the adding of some cross-linking agent or with the increasing of flexibility of shell materials. The latent energy of our N/MEPCMs were up to 102J/g. Compared to the other two N/MEPCMs, N/MEPCMs enwrapping solid paraffin had almost no super-cooling phenomenon. TGA testing showed that N/MEPCMs with the protection of shell materials had good thermal stability, besides the thermal stability became better with the adding of cross-linking agent.