Energy storage and thermal decomposition performance of polyurethane microcapsules
The microcapsules were prepared by interface polymerization with polyurethane as the capsule and wall and eicosane as the capsule core.The microcapsules were characterized by optical microscope(OM)and standard electronic modules(SEM).The energy storage performance and thermal performance and its phase change mechanism were measured and analyzed by differential scanning calorimeter.The Kissinger and Ozawa methods were used to study the thermal decomposition kinetics.The results showed thatthe microcapsules were regularly spherical in shape with a dense and smooth surface morphology and little adhesion.The average particle size was 18.18 μm and the capsule wall thickness was 1.80 µm.The productivity was approximately 91.00％and the capsule core content was 58.46％.The DSC curves obtained from multiple thermal cycles all exhibited single melting peak and double crystallization peak.The simultaneous solid-solid and solid-liquid phase transitions occurred during the heating process and the phase transition process belonged to random nucleation and subsequent growth.The integral equation of the phase transition mechanism function was G(a)=-ln(1-a),and the phase change reaction was the first order reaction.There were three stages of thermal weight loss.The protective effect of polyurethane capsule wall increased the initial decomposition temperature of phase change energy storage materials by 23 ℃,and the heat storage capacity was good.According to the Kissinger equation and Ozawa equation,the activation energies of microcapsules were calculated to be 311.27 kJ/mol and 293.16 kJ/mol,respectively and the thermal decomposition process was a first order reaction..
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