Shape-Stabilization of Phase Change Materials with Carbon-Conscious Poly(hydroxy)Urethane Foams

Thermal energy regulation is a significant challenge, contributing to over 30% of annual greenhouse gas emission (GHG) emissions. Phase change materials (PCMs) offer a promising solution by storing thermal energy, which can enable the reuse of waste heat for heating and cooling; however, developing materials for shape-stabilized PCMs remains crucial. This work investigates a self-foaming poly(hydroxy)urethane (PHU), derived from a non-isocyanate polyurethane (NIPU), as a porous support for shape-stabilizing paraffinic and salt hydrate PCMs. PHU-encapsulated paraffinic PCMs exhibited excellent thermal stability over repeated cycles. Thermal stability with salt hydrate PCMs, specifically calcium chloride hexahydrate (CaCl2*6H2O), is achieved by the incorporation of 5 wt.% barium carbonate (BaCO3) into the PHU foam. This enabled stable cycling for over 48 cycles with desirable thermal properties, i.e., a melting point ~30 degrees C, high enthalpy (ca. 138 J g-1 per cycle), and a consistent freezing point ~20 degrees C, making it suitable for applications in buildings and electric vehicle battery insulation. Also, incorporating graphite (1.5-10 wt.%) into the foam enhanced the thermal conductivity of shape-stabilized CaCl2*6H2O during heating and cooling cycles. Overall, the approach detailed here offers a carbon-conscious and chemically tunable material for thermal energy storage.