Boron-modified form stable phase change materials with high energy storage, flame retardancy, and smoke suppression for advanced photo-to-heat conversion

This study developed form-stable phase change materials (FSPCMs) with high energy storage density, superior flame retardancy, and effective smoke suppression by incorporating boric acid-grafted octadecanol (BO) as the phase change material and expanded graphite (EG)/low-density polyethylene (LDPE) as the supporting matrix. To further enhance flame retardancy, ammonium polyphosphate (APP) and pentaerythritol (PER) were introduced as synergistic flame retardants. The optimized FSPCMs (60 wt% BO, 27 wt% LDPE, 3 wt% EG, 6 wt% APP, and 3 wt% PER) exhibited outstanding performance, achieving a latent heat of 122.6 J/g, a limiting oxygen index (LOI) of 23.3 % (UL-94 V-0 rating), a 78.5 % reduction in smoke production rate, a 68.3 % decrease in smoke density, and a 77.2 % photo-thermal conversion efficiency. A systematic analysis of BO's molecular structure revealed its significant influence on phase change behavior and flame-retardant properties. The boric acid grafting strategy notably enhanced BO's char-forming capability, elucidating its synergistic flame-retardant and smoke-suppression mechanisms. The developed FSPCMs hold promise to applied in energy storage and safety-critical applications.