Development of bio-based flexible polyurethane foams incorporating phase change materials for thermal energy storage applications

The fabrication of innovative polyurethane panels for energy efficiency is increasingly important and should ideally be based on sustainable, non-fossil-based feedstock. In this context, the present work reports the development of sustainable composite panels by incorporating microencapsulated phase change materials (PCMs) into flexible polyurethane (PU) foams, synthesized from a polyol derived from waste cooking oil (WCO) and a partially bio-based isocyanate. The PU-PCM panels achieved energy storage capacity up to 26.2 J/g at a maximum PCM content of 15 phr. Uniform PCM dispersion slightly reduced cell size and increased panel density (from 128 to 157 kg/m3), thereby enhancing structural support and rigidity while reducing elasticity (compression force deflection up to 234.8 kPa). Fatigue tests confirmed resistance to cyclic loading, with increased dynamic stress and stiffness due to PCM integration. Differential scanning calorimetry showed minimal enthalpy hysteresis (+0.26 J/g) and a stable phase-change temperature (36 + 0.1 degrees C), demonstrating resilience to thermal and mechanical stress. Thermal conductivity increased slightly (from 46.15 to 48.44 mW/m & sdot;K at 20 degrees C) due to the silica-based PCM shell, while thermal diffusivity decreased, favouring transient thermal regulation. Fire performance remained unaffected, likely due to the balance between the flammable paraffinic core and the flame-retardant silica shell of PCMs. Overall, bio-based PU-PCM panels show potential for transportation and construction applications owing to their lightweight, insulating, and flame-retardant properties. They offer improved sustainability and thermal-mechanical performance compared to conventional PU panels and flammable PCMs, while supporting circular economy principles by valorising end-of-life WCO.