Thermochromic films based on vanadium dioxide (VO2)/ethylene vinyl acetate copolymer (EVA) composite were developed. The monoclinic VO2 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 VO2 powder was mixed with EVA compound, using two different mixing processes. It was found that mechanical properties of the EVA/VO2 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/VO2 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 VO2 within the polymer matrix phase. Thermochromic behaviors and heat reflectance of the EVA/VO2 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.
机译：开发了基于二氧化钒（VO2）/乙烯乙酸乙烯酯共聚物（EVA）复合材料的热致变色膜。首先通过水热和煅烧工艺制备单斜晶VO2颗粒。报道了水热时间和钨掺杂剂对煅烧金属氧化物的晶体结构和形态的影响。之后，使用两种不同的混合方法，将1重量％的制备的VO 2粉末与EVA化合物混合。发现通过熔融方法制备的EVA / VO 2膜的机械性能优于通过溶液方法制备的EVA / VO 2膜的机械性能。另一方面，溶液流延的EVA / VO 2膜的可见光透射率百分比大于熔融加工的复合膜的可见光透射率百分比。这与EVA橡胶的凝胶含量不同以及VO2在聚合物基体相中的分散和分布状态有关。还验证了EVA / VO2膜的热致变色行为和热反射率。总体而言，这项研究表明，使用聚合物复合材料方法可以开发热致变色膜。在这方面，发现混合条件是影响膜的形态和热机械性能的最重要因素之一。