Phase-Change Materials as Cryo-Shock Absorbers in Rigid Polyurethane Cryogenic Insulation Foams

This study investigates the effects of microencapsulated phase-change materials (PCMs) on the density and thermal conductivity of rigid polyurethane (PU) foams, alongside their mechanical properties. Introducing PCMs into the foam composition results in increased viscosity, complicating the mixing of polyol and isocyanate components. This viscosity increase can slow the foaming rate and subsequently raise the foam density, as observed in both poured and sprayed rigid PU foams containing 5% and 10% PCM, leading to density increases of up to 9%. Despite these slight density changes, the thermal conductivity remained relatively stable due to the preservation of the foam's closed-cell structure. The mechanical evaluation revealed a decrease in compressive and tensile strength with a higher PCM content attributed to defects arising in the foam's cellular architecture. However, adhesive strength to aluminum substrates improved, particularly with 5% PCM, possibly due to a more consistent foam structure during the slower foaming process. Differential scanning calorimetry and a dynamic mechanical analysis indicated that the incorporation of PCM increased the glass transition temperature and affected the foam's mechanical properties. This research underscores the potential of microencapsulated PCMs to enhance the functionality of rigid PU foams while needing careful consideration of their concentration to avoid compromising the structural integrity.