Polybutylene succinate/cellulose nanocrystals: Role of phthalic anhydride in squeeze oriented bionanocomposites

In order to reduce agglomerations and improve the compatibility of poly(butylenes succinate)/cellulose nanocrystals (PBS/CNC) composite, phthalic anhydride was introduced during the preparation of composite via melt blending. The composites were then suffered by squeezing treatment in a two-roll milling equipment at a given temperature. In order to investigate reaction mechanism among PBS, CNC and phthalic anhydride, PBS/CNC composites were separated and then tested via FTIR and UV-vis spectrophotometer. During reactive blending, phthalic anhydride selectively reacts with CNC, at an effective grafting ratio of 0.0196, which is confirmed by titration results. Before squeezing, the crystallinity of PBS in composites are increased but the mechanical properties of composites are weakened with increasing phthalic anhydride content, which is ascribed to the plasticizing effect of phthalic anhydride. After squeeze treatment at an extension ratio of 6, the tensile strength of PBS/PA/CNC(100/2/3) is dramatically increased from 35.2 MPa to 136 MPa. WAXD results show that PBS crystal type has little change but the crystallinity is sharply increased after orientation, which mostly contributes to the improvement of mechanical properties for PBS/CNC composites.