Preparation Of Microencapsulated Phase Change Materials And Their Application In UV Curable Polyurethane Acrylate Coating

Compared to traditional solvent based coatings, UV curable coatings can not only reduce volatile organic compound (VOC) but also increase productivity and save energy. Polyurethane acrylate (PUA) is one of the common oligomers used in UV curable coatings. Since energy crisis is now up to us, energy storage plays a more important role today, which puts forward high request to the heat-storage properties of the UV curable coatings. Thermal energy storage has attracted an increasing attention recently by using phase change materials (PCMs), which can absorb, store and release large amount of latent heat during phase-change process. Microencapsulated PCMs (MPCMs) provide an effective way to prevent PCMs from leaking during use as well as increase heat transfer area and control the changes in the storage material volume as phase change occurs. By applying MPCMs to PUA coating, the heat-storage UV curable PUA coating can be obtained.The objective of this study is to fabricate the heat-storage UV curable coating by applying MPCMs to PUA coating. The MPCMs based on paraffin core and melamine-formaldehyde (MF) shell was synthesized by in situ polymerization. The MPCMs based on paraffin core and polyurea shell was also synthesized by interfacial polymerization. The effect of stirring speed, emulsification time, emulsifier amount, emulsifier type, and core/shell mass ratio on particle size, morphology, phase change properties, and thermal stability of the MPCMs was studied by using laser particle size analyzer, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopic analysis, scanning electron microscopy, differential scanning calorimetry, and thermogravimetric analysis. The results showed that the particle size and distribution of the MPCM based on MF shell decreased with the increase of stirring speed and emulsification time. Emulsifier amount affects the diameter, distribution, and morphology of MPCM. When the emulsifier amount is low, MPCM has an incompact surface and its particle distribution is broad. When the emulsifier amount is high, the surface of MPCM is rough. The core/shell ratio affects on the morphology and thermal properties of MPCM. When the core/shell ratio is high, MPCM has an incompact surface. When the core/shell ratio is low, the surface of MPCM is rough. MPCM prepared with a core/shell ratio of 75/25 have a higher efficiency of microencapsulation and better thermal properties. The particle size and distribution of MPCM based on polyurea shell decreased with the increase of stirring speed, emulsification time and emulsifier amount. The MPCMs based on MF shell have a higher efficiency of microencapsulation and better thermal properties than those based on polyurea shell. The surface of MPCM is affected by emulsifier amount and core/shell ratio. When the emulsifier amount is low or the core/shell ratio is high, the surface of MPCM is incompact. The core/shell ratio affects the thermal properties of MPCM. When the core/shell ratio is 75/25, MPCM has a higher efficiency of microencapsulation and better thermal properties.By applying MPCMs to PUA coating, the heat-storage UV curable PUA coating was prepared. The dispersion of MPCMs in coating and heat storage properties of the coating were investigated. The results illustrated that the phase-change heat-storage UV curable PUA coating can store energy and insulate heat, which can be used in architectural heat preservation.