Preparation And Modification Of Paraffin/Melamine Resin Microencapsulated Phase Change And Their Properties

The problem of energy shortage has become increasingly prominent with the development of global industry.Therefore it is particularly urgent to find new sources of energy and improving their efficiency.As a carrier of energy storage,Phase Change Material?PCM?corresponds phase change and exchanges energy according to the external temperature.Compared with other phase change material,the organic phase change materials has many advantages.However in the process of phase change,its physical properties changes as well.This may cause leaking and mixing with other materials which limits its scope of application.In this paper,using in-situ polymerization,microcapsules were synthesized with 58#paraffin wax as the core and melamine-formaldehyde resin as the shell.By the examination of different experimental conditions,improvements on the core content of microcapsules,its heat storage performance as well as its apparent morphology are made.?1?Microcapsules provides a novel solution to the leakage problem in the process of phase change.This paper focuses on the effect of different factors on microcapsules,which includes:the feed ratio,the monomers molar ratio,the hardener,the amount of SiO₂,condensation pH,the wash and slicing.Experimental results show that the microcapsules with the uniform particle size,smooth surface and high core content can be obtained under the following conditions:the control of the feed ratio is 2.0:1.0 to 2.2:1.0,the molar ratio of the monomers is 2.0:1.0,using NaCl as a curing agent,the condensation pH is controlled at 5 by first adjusting the pH value then dropping prepolymer,and using hot water and ethanol washed.?2?This paper studies the effect of different emulsification conditions and systems on microencapsulated phase change.It compares the mechanism of nonionic and anionic emulsifying surfactant in the preparation of microencapsulated phase change.When using anionic emulsifier alone,an electric double layer is formed on the surface of the droplets,which prevents the droplets merge and stabilize the emulsion;when using nonionic emulsifier alone,the nonionic emulsifier makes emulsion stable with its strong steric effects.However,in the melamine resin wall system,the electric double layer formed by the anionic emulsifier attracts the charged prepolymer,therefore the overall performance is better for anionic emulsifier.It is shown that the microcapsules perform a better apparent morphology and thermal storage when emulsifier accounts for 4%⁵%of the core content,the emulsifying temperature is 70?and the emulsifying is 1500 r·min^-1.?3?The problem of melamine resin?poor toughness,high brittleness,poor thermal stability?are solved by its modification using PEG-400,resorcinol,ethylene glycol,polyvinyl alcohol,Arabic gum,urea etc.The modified principles are discussed in order to improve the thermal stability and thermal storage properties of microencapsulated phase change.The Thermogravimetric Analysis shows that the microcapsules'decomposition temperature is increased when certain modifiers are used to substitute melamine.This implies that the modifier improves the phase change microcapsules'thermal stability and therefore broadened its application.