Study On Polymer Porous Capsule Load And Encapsulated Organic Phase Change Materials

In this paper, we focus on the preparation of polymer capsules, encapsulation of paraffin in polyvinyl chloride capsules and the method for improving thermal conductivity of polyvinyl chloride (PVC)/paraffin capsules.Through phase separation of polymer solution and the effect of catalytic hydrolysis of sodium borohydride to generation pores and cavity respectively, a serial of PVC capsule,polyvinylidene fluoride (PVDF) capsules and polysulfone (PSf) capsules were prepared. And PVC/paraffin composite phase change material was prepared by adsorbing paraffin into cavity of capsules. Using the interfacial polymerization reaction of piperazine and trimesoylchloride, the hydrolytic polycondensation reaction of tetraethyl orthosilioate and self-polymerization of dopamine, polyamide (PA) layer, silicon dioxide layer and polydopamine (PDA) layer were formed layer by layer on the surface of the capsules. According to different order and numbers of the coating layers, PA capsule, SiO2 capsule, PA/PDA/SiO2 capsule and SiO2/PDA/SiO2 capsule were obtained. The morphology and microstructure of the capsules were characterized by field emission scanning electron microscope (FESEM) it was found that a larger hole inside the capsule and micropores in the shell of the capsules, which benefit the adsorption of paraffin in the capsules, elemental analysis, thermal stability were systematically Phase change enthalpy and phase change temperature of the capsules with different coating layers were studied by differential scanning calorimetry (DSC). The enthalpy value of fusion and solidification of the coated capsules was about 120 J/g. Thermal stability of the capsules was studied by thermal gravity analysis (TGA) and it noticed that the matters were stable without degradation in the phase change temperature range. Seal tightness was tested by experiment of thermal cycle, We can find from thermal cycle, the weight loss percentage of coated capsules with three layers was less than -5% when standing time was more than one day. In addition, the effects of skin layer and storage time were discussed as well.In order to improved thermal conductivity of capsules, different content graphite was added to the polymer solution. We concluded that the more of graphite, the poorer of sealing.