The Properties Of Fatty Acid/n-octadecane@amino Resin Microcapsules And Their Undercooling Behavior

Phase change material can absorb or release a large amount of latent heat through its own phase state change,but its temperature can remain unchanged.It is a kind of material that can be used repeatedly and has been widely used in many fields.Phase change material microcapsule is a kind of composite phase change material with a coreshell structure formed by covering the phase change material with a stable wall material.The phase change material can be protected and the performance is more stable.However,phase change material microcapsules has a very obvious problem: undercooling,what is the reduction of crystallization temperature,which is extremely unfavorable for energy storage and application.The purpose of this project is to solve this defect.In this project,n-octadecane @ amino resin microcapsules and microcapsules containing octadecanoic acid and hexadecanoic acid were successfully prepared by insitu polymerization.The effects of the addition of fatty acids,the core-wall ratio,and the amount of emulsifier on the properties of the microcapsules and the crystallization behavior were investigated,and the non-isothermal crystallization kinetics of the microcapsules was studied.The morphology,thermal performance,and thermal stability of the microcapsules were characterized by means of cold field scanning electron microscope(SEM),differential scanning calorimeter(DSC),and thermogravimetric analysis(TG).The experimental results showed that:1.The n-octadecane @ amino resin microcapsules were successfully prepared.The capsules have a regular shape and smooth surface.Compared with octadecane,the thermal properties and thermal stability of the capsules change significantly,which also indicates that the wall material has a protective effect.But the supercooling of the microcapsules is serious,and the degree of supercooling is as high as 22.6°C.2.The addition of octadecanoic acid and hexadecanoic acid does not affect the formation and thermal stability of the microcapsules.But it does affect its morphology to some extent,such as the decline in overall regularity,the untidy surface,and the serious agglomeration.However,it can obviously improve the supercooled crystallization of microcapsules,and the effect of octadecanoic acid is better than that of hexadecanoic acid.When the amount of addition is 0.05 g,the degree of supercooling of microcapsules added with octadecanoic acid is only 10°C,and the enthalpy of heterogeneous nucleation crystallization account for up to 75.21%.In addition,the effects of the core-to-wall ratio on the microcapsules were also studied.The results proves that the core-to-wall ratio has an effect on the surface morphology and thermal properties of the microcapsules,and has little effect on the thermal stability.The amount of emulsifier only affects the morphology of the microcapsules and has no effect on its thermal properties.3.Through DSC tests and analysis of related data on different cooling rates of noctadecane and n-octadecane microcapsules,it can be obtained that an increase in the cooling rate will lead to aggravation of the supercooling phenomenon.Ozawa nonisothermal crystallization kinetics theoretical study proves that the addition of octadecanoic acid can induce heterogeneous nucleation,and then affect the crystallization behavior of the microcapsules.