Fabrication of microfibrillated cellulose reinforced polypropylene composites assisted by a synergistic strategy of pre‐quaternization and paper‐making process

Abstract To tackle the ease of aggregation issue of highly hydrophilic microfibrillated cellulose (MFC) in polypropylene (PP) that thus results in an undesired reinforcing effect, this work developed an effective and industrially feasible strategy combining pre‐quaternization of pulp fibers with paper‐making process to fabricate PP/MFC composite with enhanced performance. Effects of MFC consistency, maleic anhydride grafted polypropylene (MAPP) content, and plasma treatment of chopped PP fibers on the mechanical and thermal properties of resultant composites were systematically investigated. The surface‐quaternized MFC obtained by a low‐consistency refiner (L‐MFC) exhibited a higher aspect ratio and degree of fibrillation than the corresponding surface‐quaternized MFC obtained by a high‐consistency one (H‐MFC). It was found that there existed a synergistic effect between pre‐quaternization and the paper‐making process in promoting the dispersion of MFC in PP. As compared with L‐MFC, a higher reinforcing efficiency on PP was achieved for H‐MFC, which was because the former one was more prone to form the fibril aggregates in the PP matrix. Due to both the entangled network of MFC and its nucleation effect on PP, the heat deflection temperature (HDT) of resulting composites was largely increased up to 159.9°C, an increase of 68.7°C with respect to that of PP. Highlights The H‐MFC yielded a superior reinforcement on PP than L‐MFC. The optimum mechanical properties of PP/composites were achieved at 15% MAPP. Interfacial bonding between PP and H‐MFC was enhanced by plasma treatment. An increase in Tc of the PP matrix was noted for PP/MFC. A maximum increase of 159.9°C in HDT was achieved for PP/MFC.