Preparation And Performance Of Microcapsules With Organic Reversible Thermochromic Materials As Core

Organic reversible thermochromic material is a type of compound material,the color can repeatedly change at predetermined temperature when it is heated or cooled. Color former, developer and solvent are the main ingredients of the material according to the mechanism of electron donating-accepting. But the color reverse of thermochromic compound suffers from acid,alkali and organic solvents. The resistance to acid, alkali and organic solvents of the compound material can be greatly improved by means of microencapsulation. More practical applications can be developed in the compound material solvent resistance and its application field. The screening of developers,microencapsulation of the compound material and the performance of the microcapsule are the focus of the thesis. The main conclusions are as follows:(1) Crystal violet lactone(CVL) as coloring agent, cetyl alcohol(CA) as solvent,pyrogallic acid(PA), 4- methoxy phenol(MP) and 4,4’-dihydroxy diphenyl sulfone(SDP)are suitable developers from lauric acid, myristic acid, palmitic acid, stearic acid,pyrogallic acid, tannic acid, 2,6-Di-tert-butyl-4-methylphenol, 8-hydroxy quinoline,4,4’-dihydroxy diphenyl sulfone and 4-methoxyphenol; The color change of the compound can be measured by absorbance, the compounds have maximum absorbance at 610 nm.According to the maximum absorbance,The optimum mass ratio of the compounds are :CVL:PA:CA=1:1:50,CVL:MP:CA=1:3:30,CVL:SDP:CA=1:1:50. The absorbance of CVL/PA/CA, CVL/MP/CA and CVL/SDP/CA are 1.188, 1.449 and 0.845. It were found that the reversible thermochromic compounds show good resistance to UV and the thermochromic temperature lies between 38℃and 39℃.(2) CVL/SDP/CA as core materials, three microcapsules with different shell materials were prepared. The microcapsules with urea-formaldehyde resin(UF) as shell material was fabricated by in-situ polymerization. The microcapsules with Methyl methacrylate- Divinylbenzene(MMA-DVB) polymer(MDP) and MethacrylateMethacrylic acid –Divinylbenzene(MMA-MAA-DVB) polymer(MMDP)as shell material were prepared by suspension polymerization. The morphology of the microcapsules were investigated by scanning electron microscope. The chemical structure of microcapsules were characterized by Infrared spectroscopy.The resistantce to acid,alkali and organic solvents of the microcapsules was studied. The color difference of the microcapsules with MDP and MMDP as shell materials demonstrated greater color difference than that of microcapsules with UF as shell. the stability of thermal cycling test of the former is better than that of the latter. Microcapsule with UF as shell material exhibited better resistance to solvents.