Fabrication of branching poly (butylene succinate)/cellulose nanocrystal foams with exceptional thermal insulation

Branching poly (butylene succinate) (BPBS) nanocomposite foams incorporated with cellulose nanocrystals (CNCs) were prepared by supercritical CO₂. Surface modification of CNCs by acetylation was achieved through replacing hydrophilic hydroxyl groups with hydrophobic acetyl groups, which improved the dispersibility of CNCs significantly. The crystallite sizes of CNCs and acetylated CNCs were calculated by Scherrer's formula as 25 and 19 nm, respectively. The initial crystallization temperature of diverse poly (butylene succinate) (PBS) specimens, a crucial factor for regulating cell nucleation type, increased remarkably by 11.8 °C as well as their storage modulus increased by 2 orders of magnitudes, due to branching reaction and bio-filler addition. BPBS/CNCs foam possessed a high volume expansion ratio as 37.1 times and displayed an exceptional thermal conductivity as 0.021 W(m K)^-1. This study provided a promising potential strategy to develop exceptional thermal-insulation polymer foams for composite structures, energy conservation and environment protection.