Mechanically robust and leak-resistant waterborne polyurethane/cellulose nanofibril/polyethylene glycol phase change foams for thermal energy storage

Abstract

Impregnating phase change materials (PCMs) into cellulose aerogels has been recognized as an effective approach to mitigating the liquid leakage issues because of the superior surface tension and capillary force. However, these phase change aerogels suffer from inadequate mechanical properties, making them susceptible to breakage and deformation under external forces. To address this challenge, this study explores the effects of varying waterborne polyurethane (WPU) concentrations on the mechanical and thermal properties of polyethylene glycol (PEG)/cellulose nanofibril (CNF)/WPU phase change foams, successfully fabricating a series of PEG/CNF/WPU phase change foams. Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), mechanical testing, and leakage rate tests were employed to systematically evaluate the morphology, crystalline structure, chemical composition, mechanical properties, and thermal characteristics of these foams with different WPU additions. The results revealed that the PEG/CNF/WPU phase change foam containing 9 g WPU achieved a phase change enthalpy of 134.81 J·g⁻¹, accompanied by outstanding compressive strength, compressive yield stress, and compressive modulus. Notably, the leakage rate after a 30-day leakage test was only 8.09%.

Graphical Abstract