Reversible thermochromic composites for intelligent adjustment of solar reflectance

Abstract

This paper presents a series of passive intelligent cooling materials with different colors, which can be used to alleviate the heat island effect applying in buildings. The cooling composites with intelligent discoloration and reflectance adjustment were prepared based on low density polyethylene (LDPE). Inorganic particles with different colors and thermosensitive black were introduced into LDPE to satisfy the requirements of color and cooling properties. The chromatic aberration values measured at 25 °C and 35 °C indicate that the variation of color appears on LDPE composites with intelligent color. Taking advantage of the 31 °C discoloration of thermosensitive black, the color of the samples tends to be dimmed at low temperature due to the thermosensitive black appears black, which weakens the reflectance ability of sunlight reducing cooling property and achieves partial heat retention. Above 31 °C, the color of thermosensitive black fades causing the samples to develop color. The bright colors bring higher solar reflectance reducing heat to achieve intelligent cooling. In the outdoor cooling property test, the final temperature of the glass is 65.2 °C while all samples reduce the temperature to 45.6 °C–50.6 °C, performing excellent cooling property. In addition, after thermal aging at 80 °C for 48 h as well as cold and thermal cycle tests (0 °C–80 °C) for 10 times, the composites still have good reversible thermochromic behavior showing excellent thermal aging, durability and reproducibility.