Preparation And Research Of Paraffin Composite Phase Change Materials

In recent years, green energy, including PCMs and TES, is being concerned as energy crisis and increasing pollution of energy utilization. Currently, the research focuses on organic-inorganic composite PCMs and MicroPCMs. This paper offered the preparation method using paraffin emulsion as PCM, hydrosol SiO2and PMMA separately as supporting matrix.With the effective adsorption ratio as preliminary index, water glass causing the low price and environmental as silica source were reacted to format hydrosol SiO2by sol-gel method, meanwhile, depending on SDBS for emulsifier,2600r/min of stirring rate,70℃of water bath, paraffin emulsion was obtained. Then using silane coupling agent (10wt%), PH, temperature, W/S and P/S were determined to be the technological parameter of composite PCMs, and combined soxhlet extraction and penetration circle to measure the effective adsorption ratio. Though SEM、DSC、TGA、FT-IR、hot-wire method, the characterization and service properties of high effective adsorption composite PCMs were investigated. The results demonstrate the phase change temperatures were comparable to the pure paraffin, the enthalpy ΔH=-29.3154～-104.0622J/g, went along with the effective adsorption rate increasing. And the densities of composite PCMs were0.38-0.64g/cm3. From TGA curves, the composite PCMs had two step of weightlessness, which’s able to delay thermal decomposition performance. After300times of thermal cycling, phase change temperatures varied between-3.65℃-+3.55℃, while the variation of mass were slightly greater ranging between-26.60%～-1.40%, and the enthalpy was fewer changes. Thermal conductivities of composite PCMs were measured on range of0.035-0.265W·m-1·K-1, and the heating-cooling process of the given weight (5g,10g,20g) showed the remarkable effect adjusting ambient temperature. It’s concluded certain hybridization with strong covalent bond had been generated between paraffin emulsion and SiO2but the simple composition. By the efficacy coefficient method, integrated performance of PCMs was evaluated, and the optimal samples were C-4, D-3. Efficacy coefficient of paraffin/SiO2composite PCMs system was following: D-3>C-4>A-3>B-4>A-2>B-3>A-4>D-4>C-3.Emulsifier composed of SDBS and ammonium oleate was effectively able to improve the stability of paraffin emulsion. The preparation of mieroeneapsuld phase change materials (MicroPCMs) using polymer becomes hot research. By interfacial polymerization and bulk polymerization, PMMA was prepared with monomer MMA. From SEM, the grain size of microPCMs by interfacial polymerization was smaller and smooth. The phase change temperature of microPCMs was consistent with paraffin, and the enthalpy of microPCMs, nearly-55.76J/g, was higher than microPCMs by bulk polymerization. The density was about0.5538g/m3, while thermal conductivity closed to0.1000W·m-1·K-1. Paraffin/SiO2composite PCMs had better thermal decomposition stability owing to delay the temperature of weightlessness, which poses broad perspective.