Preparation of High-Performance Polyethylene Composite Materials Reinforced with Cellulose Nanofiber: Simultaneous Nanofibrillation of Wood Pulp Fibers during Melt-Compounding Using Urea and Diblock Copolymer Dispersant

Production of nanocomposites from macro-scale materials in situ in a melting compounder is highly desirable yet challenging. In this study, we develop a highly efficient approach for the preparation of cellulose nanofiber (CNF)-reinforced high-density polyethylene (HDPE) composite materials from as-received wood pulp fibers, in which nanofibrillation-assisting plasticizers (urea and urea derivatives) and a diblock copolymer dispersant are used. The most effective plasticizer is urea, which plays a crucial role in producing CNF with less fragmentation during the kneading step, owing to the plasticization/nanofibrillation and the reaction with hydroxyl groups of cellulose fibers into a carbamate. The diblock copolymer as a dispersant enables the stabilization of the appropriate dispersion of the produced CNF in nonpolar HDPE. The resulting composites exhibit significantly improved mechanical properties, including a 6.9-fold increase in the Young’s modulus with 10 wt % loading of wood pulp fibers over that of neat HDPE.