Effect of acetylated cellulose nanocrystals on solid-state foaming behaviors of chain-extended poly(butylene adipate-co-terephthalate)

Fully biodegradable chain-extended poly(butylene adipate-co-terephthalate) (CPBAT)/acetylated cellulose nanocrystals (ACNCs) nanocomposites were prepared by the melt compounding process. The dispersibility of CNCs in deionized water was improved through the surface acetylation, which was observed by atomic force microscope and transmission electron microscope. The chain extender was added to the PBAT matrix to improve the melt strength and viscoelasticity of PBAT. The ACNC nanoparticles which served as bionano-reinforcing fillers were introduced into CPBAT to further improve the crystallization behaviors and rheological properties of CPBAT/ACNCs nanocomposites. Finally, the CPBAT/ACNCs nanocomposite foams were prepared via batch supercritical CO2 foaming process. The cell structure and morphology of various CPBAT/ACNCs foams were investigated by scanning electron microscope. It was found that the introduction of ACNC nanoparticles led to a reduction of cell size, an increase in cell density and in the uniform cell distribution owing to the heterogeneous cell nucleation effect of ACNCs. Meanwhile, the volume expansion ratio (VER) of CPBAT foams reached to 9.21 times, the highest VER reported for PBAT foam in the current literature. Also, the thermal conductive properties of nanocomposites and foams also were studied by a laser thermal conductivity analyzer.