Preparation And Performance Of Multi-microcapsules

At present,microcapsules have only one special kind of properties.In this experiment,we hope to preparate microcapsules with two or more functions via using different core materials and different shell materials,such as self-repairing,self-cleaning,conducting,absorbing,antibacterial,catalytic,heat storage and so on.Through the combination the multi-functional microcapsules with the traditional materials(coating,paint,etc.)or advanced materials,we hope to preparate a kind of composite material with the advantages of the two materials.It will have various physical and chemical properties.Microcapsules containing n-octadecane with the melting point(28.18°C)that close to room temperature as core material and urea-formaldehyde polymer with the characteristics of weak acid,alkali resistant,excellent insulation,strong wear resistance and low price as shell material were prepared by in-situ polymerization.The microcapsule has a multi-level micro-nano-structure surface and shows a multifunction of superhydrophobicity,self-cleaning heat storage and heat release.Moreover,the influences of pre-polymer temperature,pre-polymer pH value,pre-polymer molar ratio,PCM emulsion temperature,surfactant type,surfactant concentration,resorcinol,stirring speed and timeon microcapsule physical property have been researched.The optimal process for the preparation of n-Octadecane microcapsules was determined: The molar ratio of pre-polymer was 1.9:1;The reaction temperature is 70°C;pH value is 8.0;The surfactant concentration of EMA aqueous solution of 6.6 g/L,and add 4.2 g/L of Resorcinol;In the formation of microcapsules,the stirring rate was 600-1200 r/min,the temperature was 35 °C the time was 1-1.5 h,and the curing temperature of urea formaldehyde resin was 1 h.By using optical microscope,Field Emission Scanning Electron Microscope,Energy Dispersive Spectrometer,Fourier Transform Infrared Spectrometer,thermogravimetric analysis,contact angle measurement,differential scanning calorimetry and thermal imaging instrument analyze thermal stability,thermal properties,contact angle,selfcleaning performance and heat storage and heat release performance test of the microcapsules was stydied.The results indicate that the microcapsules are round,with core-shell structure,the average size was 80-20 ?m and the wall thickness was 150-400 nm.The surface of the microcapsules was rough and distributed with 200-500 nm nano-scale urea formaldehyde resin particles;The surface elements are C,H,O three elements;There was no chemical reaction between n-octadecane and urea formaldehyde resin,and the crosslinking between them was very good;Microencapsulation hindered the volatilization of noctadecane and promoted the thermal properties of n-octadecane microcapsules;The thermal properties of the n-octadecane microcapsules were slightly decreased,and the crystallization temperature and melting temperature were not changed after the 100 cycles;The microcapsule has a super hydrophobic,hydrophobic angle greater than 160 degrees,the rolling angle less than 12 degrees.After exposure to air for a long time,the contact is still greater than 160 degrees,the rolling angle is less than 12 degrees.and has a good stability under normal temperature and pressure;In the self-cleaning test,carbon black and sandy soil were used to test the microcapsules;In the test of heat release performance,the heat storage and heat release performance is good,the coating can eliminate the fluctuation of temperature to a certain extent,and the temperature is maintained at 28.2°C.