Organic Reversible Thermochromic Compounds And Their Microencapulation Research

The organic reversible thermochromic material is a special type of functional materials, whose color changing with the temperature. But this kind of material is susceptible to the external environment, have bad heat stability, bad resistance to acid and base. The use of microencapsulation technology can solve these problems to some degree, and expand the applications of these materials.In this paper, it selected ODB-1, bisphenol AF and benzophenone as color-changing system of organic reversible thermochromic compound, it was analysed by DSC, FT-IR, XRD, and determined its color-change mechanism was the mechanism of electron exchange in intermolecular. Then microencapsulation the benzophenone compound and testing their performance. When prepared benzophenone compound microcapsules, the quality ratio of core material was m1(ODB-1):m2(bisphenol AF):m3(benzophenone):m4(1,10-decanediol)=1:2:30:8, urea-formaldehyde resin as wall material, 3wt% arabic gum as emulsifier, the average particle diameter was 3.15?m. The optimal conditions for preparation of urea-formaldehyde resin prepolymer were: the molar ratio of urea and formaldehyde was 1:1.9, the pH during prepolymerization was 8.0, the reaction temperature was 70 oC, the prepolymerization time was 1h. Control the endpoint pH value was 2.5 at the microcapsule formation stage, and selected NH4 Cl as acid catalyst. The testing results showed that microencapsulation can improve the heat stability, acid and base resistance of organic reversible thermochromic material effectively, and does not affect the color performance.Next, the microcapsules were prepared by the method of in-situ polymerization with urea-formaldehyde resin as wall material and phenyl salicylate, octadecanol compounds as core material respectively, and optimize the preparation conditions. When prepared phenyl salicylate compound microcapsules, the quality ratio of core material was m1(ODB-1):m2(bisphenol AF):m3(phenyl salicylate):m4(octadecanol)= 1:2:60:4. A mixture of 4wt%SMA(pH=4)/4wt%SMA(pH=3.5)/1wt%SAS was selected as emulsifier with the stirring rate of 3000 rpm. As a result, the microcapsules' size distribution was uniform without adhesion, the average particle diameter was 4.02?m. The quality ratio of core material was m1(ODB-1):m2(bisphenol AF):m3(octadecanol)=1:2:60 in the preparation of octadecanol compound microcapsules, the optimal emulsifier was 1wt%(SDS/Tween-80)/8wt% SMA(pH=4). And when the quality ratio of emulsifier and core material was 4:1, stirring rate was 10000 rpm, the average particle diameter of microcapsules was 3.28?m, the size distribution was uniform, meet the requirements of practical applications.