Influences of dispersion media for chemically modified cellulose nanofibers on rheological and mechanical properties of cellulose nanofiber reinforced high-density polyethylene

Cellulose nanofibers (CNFs) have exceptional mechanical and thermal properties, but the use of these materials to reinforce polyolefins is challenging. In the present study, ethanol, acetone, isopropyl alcohol (IPA) and water were used as dispersion media for alkenyl succinic anhydride-modified CNFs (ACNFs). Masterbatches were prepared from these ACNFs wetted in the various liquids and then melt-compounded with high-density polyethylene (HDPE) using a twin-screw extruder, followed by injection-molding. The morphologies of the resulting HDPE/ACNF composites were characterized using optical and electron microscopy, and the rheological and mechanical properties of these composites were also evaluated. The results showed that the storage and loss moduli as well as the tensile moduli and strength of the composites produced using the organic liquids were higher than those of the composite made using water, owing to the better dispersion of ACNFs in the HDPE matrix in the former. This improved dispersion would be expected to increase the contact area between the ACNFs and the matrix and to enhance the orientation of the HDPE molecules. IPA was found to give the highest tensile modulus and strength among the organic liquids used in this study. The tensile modulus and strength of the composite containing ACNFs produced from IPA were, respectively, four times and two times higher than those of the neat HDPE. IPA is a relatively non-toxic, inexpensive compound, and so could be readily adopted for industrial scale processing.