Preparation of polyvinyl chloride capsules for encapsulation of paraffin by coating multiple organic/inorganic layers

Abstract

Abstract Hysteresis of phase transition and leaking of phase change matters are main problems in encapsulation of phase change materials. In this paper, we aimed to solve the problems by coating multiple organic/inorganic layers on surface of capsules adsorbed with paraffin. The coating layers are formed through interfacial polymerization of piperazine and trimesoylchloride or polycondensation of tetraethyl orthosilicate, or self-polymerization of dopamine. Morphology and surface elemental analysis were observed by field emission scanning electron microscope and X-ray energy dispersive spectrometer, indicating formation of thin and dense coating layers. Thermal stability and phase change properties were characterized by thermal gravity analysis and differential scanning calorimetry. Phase change enthalpy and phase change temperatures of the coated capsules were similar whatever the coated layers were, suggesting little influence of coating layers on the phase change process. Tightness of encapsulation was evaluated by measuring weight loss percentage (WLP) of the capsules under repeated heating of the capsules at 70 °C. It was noticed that the capsules coated with three layers owned a WLP less than −5% withstanding for more than one day. Standing time and valid space were found to be important for tight encapsulation.