Preparation And Application Of Paraffin Microcapsule Phase Change Energy Storage Materials

As an organic phase change material for thermal energy storage,paraffin wax has advantages of wide phase change temperature,high energy storage density and large enthalpy in the process of phase change.Base on the above advantages,paraffin wax is widely used as thermal energy storage material.Core-shell Microcapsules formed by paraffin wrapped by high polymer is widely used in aerospace,military,construction,textile and other fields.In this dissertation,phase change material microcapsules for energy storage composed of paraffin core and styrene,methacrylic acid,methyl methacrylate shell was synthesized by suspension polymerization method.Phase change material microcapsules were also synthesized by micro emulsion polymerization method with cetyltrimethylammonium bromide,sodium dodecyl sulfate,tween 60,polyvinylpyrrolidone and complex surfactant as an emulsifying agent,respectively.The paraffin phase change material microcapsules were characterized using Scanning electron microscope(SEM),Differential scanning calorimeter(DSC),thermogravimetric analyzer(DTA,TG)Fourier transform infrared spectrometer(FT-IR)and other modern characterization methods.Various factors affecting the storage heat properties of paraffin phase change material microcapsules were inverstigated,including the ratio of core material to monomer,the ratio of copolymerization monomer to copolymerization monomer,the dosages of emulsifier,the dosages of initiator,rotation speed and polymerization temperature.The encapsulation efficiency of phase change material microcapsules prepared by micro emulsion polymerization method using compound surfactants as an emulsifying agent reached 83.96%,which is the highest result until now.The core-shell phase change material microcapsules were added into cement blocks,and the flexural and compressive strength of cement blocks were evaluated.(1)paraffin@styrene-methyl acrylic-methyl methacrylate polymer P(St-MAA-co-MMA)phase change material microcapsules were prepared Using suspension polymerization method.According the results,the particle size of phase change material microcapsules is ca.1 μm,the latent heat of phase change material microcapsules is 131.13 J/g,and the encapsulation efficiency of phase change material microcapsules is 66.11%.(2)paraffin@ binary copolymer phase change material microcapsules were prepared Using micro emulsion polymerization method.paraffin@Styrene-methacrylic copolymer P(St-co-MAA)phase change material microcapsules were prepared with diethylbenzene as crosslinking agent.The particle size of paraffin@P(St-co-MAA)are 0.5 to 1 μm.The enthalpy of phase transformation of paraffin@P(St-co-MAA)is ca.104.68 J/g,and the encapsulation efficiency of paraffin@P(St-co-MAA)is ca.43.16%.The phase change microgel with uniform morphology was prepared by using styrene-methylacrylic acid copolymer P(st-co-MAA)as wall material and paraffin as core material.The particle size of phase change microgel is ca.400-600 nm,the latent heat of phase change microgel is 89.05 J/g,and the encapsulation efficiency of phase change microgel is 28.35%.paraffin@ Styrene-methacrylic copolymer P(St-co-MAA)phase change material microcapsules were prepared.The particle size of paraffin@P(St-co-MAA)is 300-450 nm,the latent heat of paraffin@P(St-co-MAA)is 80.36 J/g,and the encapsulation efficiency of paraffin@P(St-co-MAA)is 20.18%.Paraffin@ Styrene-methacrylic copolymer P(St-co-MAA)phase change material microcapsules were prepared with diethylbenzene as crosslinking agent.The particle size of paraffin@P(St-co-MAA)is 1-2 μm.The latent heat of paraffin@P(St-co-MAA)is 152.51 J/g,and the encapsulation efficiency of paraffin@P(St-co-MAA)is 61.61%.Octadecane@Styrene-methacrylic copolymer P(St-co-MAA)phase change material microcapsules were prepared with diethylbenzene as crosslinking agent.The particle size of octadecane@P(St-co-MAA)is ca.400-520 nm.The latent heat of octadecane@P(St-co-MAA)is 216.21 J/g,and the encapsulation efficiency of octadecane@P(St-co-MAA)is 83.96%.(3)The phase change material microcapsules were added to the cement blocks,and the compressive and flexural strength of the 3d cement block was investigated.Experiments show that when the addition amount of microcapsules prepared with cetyltrimethylammonium bromide and polyvinylpyrrolidone as micro emulsifiers is3% of the standard sand mass,the compressive strength of the cement block is 17.23 MPa and 17.95 MPa.When the added amount of the microcapsules prepared with the compound surfactant is 5% of the standard sand mass,the flexural strength of the cement block is 3.51 MPa.