Reinforcement effect of cellulose nanowhisker on bio-based polyurethane

Bio-based polyurethane (BPU)/cellulose nanowhisker composites synthesized using castor oil-based polyol were prepared by adding cellulose nanowhiskers during preparation of the prepolymer. Chemical modification of cellulose nanowhiskers was performed to enhance dispersion of the cellulose nanowhiskers, and modified cellulose nanowhiskers (m-CNWs) were covalently bonded with the BPU matrix to improve interfacial adhesion. The tensile strength and modulus of the m-CNW reinforced BPU composites were significantly improved, as compared with the neat BPU. The elongation at break of the BPU/m-CNW composites decreased with increasing m-CNW content, indicating that m-CNW made the BPU stiff and rigid. Dynamic mechanical analysis showed that the storage modulus was increased and the loss tangent peak was shifted toward higher temperatures by incorporation of m-CNW. This was due to the increased cross-linking density of the rubber network resulting from the strong interaction between m-CNW and the BPU matrix. Furthermore, the m-CNW enhanced the thermal stability of the BPU composites. This research demonstrated the potential for utilization of cellulose nanowhiskers as eco-friendly reinforcement in biopolyurethane composites.