Effect of surface modification on the dispersion, rheological behavior, crystallization kinetics, and foaming ability of polypropylene/cellulose nanofiber nanocomposites

Herein, the issue of dispersing cellulose nanofiber (CNF) in hydrophobic polymer has been solved through the modification of the CNF surface using alkenyl succinic anhydride (ASA). Polypropylene (PP) nanocomposites containing CNF with various degrees of substitution (DS) - ranging from 0 to 0.4 - were prepared by melting and blending in an extruder. Fourier transform infrared spectroscopy (FTIR) results illustrated that the ASA chains were successfully incorporated into the CNF, and the FTIR spectroscopic imaging and X-ray computed tomography demonstrated the well-dispersed hydrophobic-modified CNF with the highest DS (= 0.4) in the PP matrix. Rheological results revealed that a network-like structure of CNF was generated in the PP/CNF nano composites. Compared with isotactic PP, the PP/CNF composites exhibited improved crystallization kinetics, which could be elucidated via fast scanning chip calorimetry (FSC) analysis. Finally, the foaming performance of the prepared composites was examined using an easily scaled foam injection molding technique. The incorporation of CNF remarkably ameliorated the cellular morphologies of PP foams, resulting in a sharp decrease in cell size and a notable enhancement in cell density.