Study On Microencapsulation Of New Reversible Thermochromic Materials

Reversible thermochromic materials are high practical valued in industry, national defence and daily life etc. Now, more and more attention has been paid to the microcapsule-type reversible thermochromic materials because of its high performance of reversibility, stability and compatibility. In view of reversibility thermochromic material's questions, such as backward preparation technology, instable performance, this paper proposed the reversible thermochromic materials are microencapsuled, the poly(methylmethacrylate) (PMMA) as the shell material, which in order to solve such questions as the low thermochromic sensitivity, the bad compatibility, the low reversibility and instability etc. It is worthy of noting that the difficulty of microcapsule with water-soluble materials preparation is also solved in this paper.This thesis used new preparation method of microcapsule——Internal PhaseSeparation from Diphase Emulsion method, which combine oil phase separation method with solvent evaporation method as well as the thermochromic materials' unique nature, the poly(methylmethacrylate) (PMMA) as the shell material, acetone-water mixtures solution for the cosolvent, liquid paraffin for the continuous phase, sorbitan monooleate (Span80) as the emulsifier, successfully prepared new reversible-thermochromic-type CC/PMMA microcapsule. The roles which affect on the embedding efficiency and particle size of the CC/PMMA microcapsule played by six factors: the ratio of core and shell, emulsifier, the ratio of acetone and water, emulsified time, the rate of stirring and the way of joined emulsion in the formation. Through orthogonal-designing experiments, the relation between the different factors and the thermochromism performance of the CC/PMMA microcapsule are thoroughly analyzed. The factors considered in the experiments are the ratio of core and shell,the mass of emulsifier, the ratio of acetone and water and emulsified time. Microstructure of the CC/PMMA microcapsule is characterized by Biomicroscope, Scanning Electron Microscopy and Differential Scanning Calorimeter. The mechanism of the Internal Phase Separation from Diphase Emulsion method, the relation between the structure and thermochromism performance of the CC/PMMA microcapsule arestudied. Besides, the stability > solvent resistance > the environment adaptability and polymer compatibility of the CC/PMMA microcapsule are also investigated. Then the effects on thermochromism and project performance of the coating and paint in different content of the CC/PMMA are discussed. The results offer certain theory-base for the preparation and application of microcapsule-type reversible thermochromic materials.The result has shown that: in the means of Internal Phase Separation from Diphase Emulsion method, the best choice is that the ratio of core and shell is 1 '. 1, the mass of emulsifier is 9wt%, the ratio of acetone and water is 20 ' 1, emulsified time is 30min, the rate of stirring is 2000rad/min, and the way of joined the emulsion should be rapid. The average diameter of microcapsule is 1.2um, shell thickness is 0.2um. The CC/PMMA microcapsules have smooth surface, mean droplet diameter and a narrowing of the size distribution. The temperature of color changing of CC/PMMA microcapsules is 41°C, the time of color fading of CC/PMMA microcapsule is 53s. Its color changes reversibly from pink to blue. The results presentes offer an outstanding CC/PMMA microcapsule and show that the reversible thermochromism, environment adaptability and polymer compatibility of the CC/PMMA microcapsule are improved by microencapsulation. At the same time, the CC/PMMA microcapsule overcomes the weakness with depending on environment. So this thesis attains to the test purpose and request, and e the CC/PMMA microcapsule has possessed a prospected applications.