Oligoether grafting on cellulose microfibers for dispersion in poly(propylene glycol) and fabrication of reinforced polyurethane composite

Abstract Application of cellulose microfibers as a reinforcing agent for high-performance polyurethane composites is rarely mentioned because the inherent hydrophilicity combined with the adverse aspect ratio of the fibers cause difficulties in dispersion within and compatibility with the polymer matrix. Here, we propose a feasible approach to graft oligoethers synthesized by ring-opening polymerization in a heterogeneous reaction to the cellulose microfiber surface. The oligomers composed of ether linkages and flexible hydroxyl groups provide cellulose fibers with good dispersity in poly(propylene glycol) and potential physical and chemical cross-linking points in reaction with isocyanates to form good interfacial adhesion between the fibers and the polyurethane matrix. Consequently, the tensile properties and viscoelasticity of the oligomer-grafted cellulose-filled polyurethane composite were enhanced compared with those of the neat elastomer and composite containing pristine cellulose microfibers. This reinforcement effect is attributed to the natural stiffness of the fiber bundles and the cross-linking network generated by the oligomers grafted on the fiber surface.