Thermal stability of organic Phase Change Materials (PCMs) by accelerated thermal cycling technique

Abstract

Phase change materials (PCMs) can improve thermal comfort of occupants acting as thermal energy storage systems. During their service life, PCMs undergo many phase change transitions. However, there is a lack of feasible and cost-effective techniques to evaluate the effect of thermal cycling on the long-term stability and performance of PCMs, which can influence their selection and restrict a broader acceptance of these materials by the construction sector. This study developed a novel accelerated thermal cycling multi-technique to assess the stability and reliability of PCMs under dynamic thermal conditions. All investigated PCMs showed remarkable stability in terms of phase change temperature and latent heat energy even after undergoing 10,000 thermal cycles. The Thermogravimetric Analysis (TGA) results underscore the suitability of these PCMs for built environments, with minimal mass loss at lower temperatures (below 150 °C). The Fourier Transform Infrared spectroscopy (FT-IR) and ¹H Nuclear Magnetic Resonance (NMR) results revelled no molecular changes induced by thermal cycling. The novel accelerated thermal cycling technique provides more accurate results than thermal cycling using Differential Scanning Calorimetry (DSC) only, overcoming the issues of contamination and subcooling of smaller samples in DSC measurements.