Preparation And Properties Of Paraffin/MUF Resin Microcapsules

As a material with a large heat storage,phase change material can solve the contradiction between solar thermal energy supply and demand mismatch.Paraffin is one of phase change materials,which was most commonly used in life.It has the advantages of high latent heat of phase change,low cost,etc However,there are also defects such as poor thermal conductivity and leakage of solid-liquid phase The microencapsulation of paraffin can solve these problems wellIn this paper,for the occasion of heat storage in solar drying of wood,58#solid paraffin was selected as the core material and melamine-urea-formaldehyde(MUF)resin was used as the wall material to prepare Paraffin/MUF Resin wax microcapsules.It is proposed to use this microcapsule in the heat storage system of the above-mentioned occasion to improve its energy storage efficiency.The main research contents and results of this paper are as follows(1)Paraffin/MUF Resin microcapsules were prepared by in-situ polymerization.The effect of molar ratio of urea to melamine,core/wall ratio,emulsifier OP-10 dosage,emulsification stirring speed,NaCl content,reaction temperature and pH value on the capsule heart rate,coverage and yield of paraffin wax microcapsules were investigated.The optimized process parameter was that the molar ratio of melamine to urea was 2:3,core/ratio(mass)was 2:1,emulsifier OP-10(mass fraction of core material)was 7%,and the stirring speed was 1000r/min,the amount of NaCI(mass fraction of the core material)was 18%,the reaction temperature was 80℃,and the pH value was 2.5.The verification test was conducted by using the optimized process parameters as the process conditions,and the test results were analyzed The results showed that the microcapsule capsule heart rate was 58.8%,the coverage rate was 50.53%,the yield was 67.1%,and the thermal conductivity was 0.1898W/(m·k),which reached 63.3%of the thermal conductivity of paraffin(0.3 W/(m·k)).The test results have been greatly improved compared to the single-factor test results.(2)Microcapsules were characterized by differential scanning calorimetry(DSC),thermal gravimetric analyzer(TGA),Fourier transform infrared spectrometer(FT-IR)and scanning electron microscope(SEM).The DSC test showed that the phase change enthalpy of the microcapsules was 95.59 J/g,which has good thermal performance.TGA test results showed that the heat loss rate of paraffin wax was significantly slower and the initial temperature and final temperature of weight loss were higher than uncoated paraffin,indicating that the microcapsules effectively enhance the thermal stability of the paraffin wax.The FT-IR spectrum showed a broad absorption peak at wavenumber 3417cm-1 and absorption peak at wavenumber 1006cm-1.The presence of these characteristic peaks indicates that MUF resin was formed,and paraffin was not involved in the reaction.The results of SEM showed that the microcapsules were spherical in shape and uniform in size with a particle size about 1.5～5μm.However,the surface was rough and agglomeration occurred.