Preparation and Characterization of Microencapsulated Phase Change Liquid Paraffin
液体石蜡相变微胶囊的制备及性能表征

As a novel type of low-temperature phase change materials, the microcapsules with the core of liquid paraffin and shell of melamine-formaldehyde resin (MF resin) were synthesized by using in-situ polymerization process. The effects of emulsion formulations, pre-polymerization conditions, shell material content and reaction time were investigated to obtain the optimized microcapsules. The as-prepared products under the optimal conditions showed high quality, their surface was smooth and dense, and free of any adhesion. The experimental characterization showed that in the microcapsules over 75%(ω) paraffin liquid was well encapsulated by MF resin, of which the thickness was in the range of no less than 50~100 nm. The microcapsule size was within the range of 1~5 μm and most intense distribution at 3.32 μm. DSC measurements gave two endothermic peaks with the initial phase change temperatures of 4.4 and 28.6℃ respectively, and the total enthalpy was 14.9 J/g which is comparable to the latent heat of commercial liquid paraffin. The microcapsules keep stable up to a high temperature 215℃ or a pressure of 1.0 MPa, as well as excellent thermal resistance against long-term thermal aging and thermal cycle near 300 times.