Preparation, Characterization and Thermo-Chromic Properties of EVA/VO(2) Laminate Films for Smart Window Applications and Energy Efficiency in Building

Thermochromic films based on vanadium dioxide (VO(2))/ethylene vinyl acetate copolymer (EVA) composite were developed. The monoclinic VO(2) particles was firstly prepared via hydrothermal and calcination processes. The effects of hydrothermal time and tungsten doping agent on crystal structure and morphology of the calcined metal oxides were reported. After that, 1 wt % of the prepared VO(2) powder was mixed with EVA compound, using two different mixing processes. It was found that mechanical properties of the EVA/VO(2) films prepared by the melt process were superior to those of which prepared by the solution process. On the other hand, percentage visible light transmittance of the solution casted EVA/VO(2) film was greater than that of the melt processed composite film. This was related to the different gel content of EVA rubber and state of dispersion and distribution of VO(2) within the polymer matrix phase. Thermochromic behaviors and heat reflectance of the EVA/VO(2) film were also verified. In overall, this study demonstrated that it was possible to develop a thermochromic film using the polymer composite approach. In this regard, the mixing condition was found to be one of the most important factors affecting morphology and thermo-mechanical properties of the films.