Preparation, Characterization and Thermo-Chromic Properties of EVA/VO₂ Laminate Films for Smart Window Applications and Energy Efficiency in Building.

Onruthai Srirodpai,Vissanu Meeyoo,Kitti Yuwawech,Saiwan Nawalertpanya,Jatuphorn Wootthikanokkhan

doi:10.3390/ma10010053

Abstract

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.

Highlights

It has been reported that energy use for heating and air conditioning (HVAC) accounted for48%, 55% and 52% of buildings’ energy consumption in the USA, UK and Spain [1], respectively.To reduce the energy consumption in buildings, there has been a considerable interest in a development of so called “energy efficient windows” or “smart windows”
The characteristic XRD peaks at 2 theta of 27.11◦, 34.49◦, 39.59◦, and 56.33◦, representing the VO2 (B) phase, can be observed after the hydrothermal treatment. These correspond to the (−311), (−312), (−222), and (−531) planes of the metal oxide crystal
By further treating these materials through the calcination process, the above XRD peaks disappeared whereas those of which representing the characteristic pattern of monoclinic vanadium dioxide (VO2 (M)) immerged

Summary

Introduction

To reduce the energy consumption in buildings, there has been a considerable interest in a development of so called “energy efficient windows” or “smart windows” This effect can be achieved by several approaches including by coating chromic material onto glass substrate. Materials 2017, 10, 53 be responded to the environmental temperature and yet the visible light transparency of the thermo-chromic smart windows remains almost unchanged Transition metal oxides such as Ti2 O3 , V2 O3 , and VO2 are known to be capable of exhibiting thermo-chromic behavior. These materials are basically semi-conductors at low temperature and change to a metallic state at a temperature above its critical transition temperature. Wang et al [4] reported that co-doping of VO2 with tungsten (W) and magnesium (Mg) could provide a synergistic effect in which both transition temperature and luminous transmittance of the VO2 film can be improved

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