Photodegradation Studies of Pristine and Microencapsulated Thermochromic Coatings for Energy Savings in Outdoor Applications

Organic and polymer encapsulated thermochromic materials have potential use as energy savers in building envelopes, due to the fact that their colour chromatic behaviour changes with temperature. External stimuli, such as solar radiation, often causes degradation in the physicochemical characteristics that impact their optical performance in real-time outdoor applications. The off-the-shelf polymeric encapsulated thermochromic dyes blended in a sodium silicate binder were prepared as coating materials on glass substrates using a dye-casting process with a film thickness of approximately 300 µm. These films have been systematically exposed to extended simulated sunlight environments at ambient conditions. The optical absorption and colour chromatic characteristics using UV–Vis spectroscopic and CIE calorimetric measurements were evaluated and compared with those of the pristine samples for photodegradation and related processes. We have also attempted to microencapsulate these thermochromic dyes and characterized via Fourier transform infrared, to understand the chemical make-up of the encapsulants for possible degradation mitigation of the dyes, and these results are also presented and discussed in this study.