Study On Microencapsulation Of High Reversible Thermochromic Materials

Presently, the reversible thermochomic materials have become a hotspot of researching, and have high practical valued. Water-solubility inorganic thermal materials were wrapped by microencapsulation method in this paper, which in order to enhance the reversibility and extend the using area of different temperature.In this thesis, using inorganic pigment (NLHN), ethyl cellulose (EC), cyclohexane (HC), Span-80 and poly-isobutylene (PIB) to prepare S/O type NLHN-RTM microcapsule by oil phase separation method in which NLHN EC, HC, Span-80 and PIB are used as core materials, shell materials, solvent, emulsifier respectively and phase stabilizer. The roles which act on the particle size and embedding efficiency of the S/O type NLHN-RTM microcapsule played by six factors: the ratio of core and shell, emulsifier concentration, solvent content, stabilizer content, surface tension, and the rate of stiring. The relation between the different factors and the thermochromism performance of S/O type NLHN-RTM microcapsule are discussed, which considered the performance of core, the thickness of shell, the rate of stiring and the rate of cooling. Microstructure and thermochromism performance of the S/O type NLHN-RTM microcapsule are characterized by Biomicroscope, Scanning Electron Microscopy, Thermal Gravimetric Analysis and Fourier Transform Infrared spectroscopy, and the particle size, thickness of shell, embedding efficiency, heat resistance, chemical stability, mechanism resistance and environment resistance, of the S/O type NLHN-RTM microcapsule are investigated, and the structure and performance of the NLHN-RTM microcapsule are discussed. Then the effects on thermochromism and project performance of the S/O type NLHN-RTM microcapsule in PVA elements coating, alkyd varnish coating and latex paint are discussed.The results have shown that: the best choice is that the ratio of core and shell is 2 : 3, the mass of solvent is 70ml, the mass of emulsifier is 5wt%, emulsified time is 40min, the rate of stirring is 1000r/min, and the mass of phase stabilizer is 3wt%. The temperature of color changing of the S/O type NLHN-RTM microcapsule is 109.5℃, while the time of color changing is 60s, and the temperature and the time of color fading are 108℃ and 120s, and the sensitivity of color changing is 0.315 respectively. And it's color changes reversibly from green to purple. As a conclusion, the reversibility and sensitive are improved by microencapsulation, and high performances and prospected applications.