Rigid polyurethane foams incorporated with phase change materials: A state-of-the-art review and future research pathways

Taking the joint advantages of the thermal energy storage capacity of phase change materials (PCM) and the excellent thermal insulation performance of rigid polyurethane (PU) foams, much attention has been paid to an idea that incorporates PCM into PU foam to promote energy efficiency in buildings. In this paper, a comprehensive review of PU–PCM foams was conducted from the perspectives of synthesis methods, phase change characterization, mechanical strength, cell morphology, thermal performance et al. It is shown that thermal energy storage capacity in PU–PCM foam is enhanced significantly while mechanical strength is decreased with respect to pure PU foam. Thermal conductivity was only investigated by one group with a conclusion that it maintains nearly constant when having PCM content increased. The authors strongly suggest more research work on this topic. In order to modify this new thermal insulating material, some other future research opportunities, such as formulation recipe improvement, thermal insulation performance, thermal aging and general energy saving evaluations, are explored to improve this composite. A challenge is also raised related to the low active thermal capacity of the PCM with fixed phase change temperature within a temperature gradient in the PU layer with low thermal conductivity.