Mechanical properties of polypropylene composites reinforced by surface-coated microfibrillated cellulose

Polypropylene (PP)/microfibrillated cellulose (MFC) composites were prepared by coating nano to sub-micrometer width and several micrometer length MFC with a surfactant, polyoxyethylene (10) nonylphenyl ether. The composites were produced by melt compounding using a twin screw extruder and subsequent hot compression or injection moldings. Although the coating provided good dispersion of the MFC in the PP matrix, reinforcing effects on the Young’s modulus and yield strength were negligible because of weak adhesive interactions between PP and MFC mediated by the surfactant. Addition of maleic anhydride grafted PP (MAPP) to the PP/surface-coated MFC composites improved the interfacial adhesive interaction, leading to a high Young’s modulus and strength at yield while maintaining the large plastic deformation. Injection molded PP (80 wt%)/surface-coated MFC (10 wt%) composites containing 10 wt% MAPP showed 45% higher Young’s modulus and 50% higher yield strength than the neat PP.