Polystyrene nanocomposites reinforced with phenyl isocyanate-treated cellulose nanofibers

Cellulose nanofibers (CNFs) have attracted much attention as eco-friendly natural nanofillers for thermoplastic-based composites. In this work, we present one possible route to fabricating such a composite based on polystyrene (PS) polymer reinforced with chemically modified CNFs. To achieve a uniform dispersion of CNF fillers in the PS matrix and simultaneously ensure interfacial strength between CNFs and PS in the composite, the surface of CNFs was functionalized with phenyl isocyanates. The composite beads of PS and iCNF were produced by coagulation, followed by thermocompression of the composite beads to produce PS-iCNF composites. Three-point bending flexural tests were performed on the composites to evaluate their mechanical properties according to the CNF loading. The elastic modulus of the PS-iCNF composite increased gradually, while the fracture bending strength decreased as the loading increased, compared to those for the pure PS film. SEM analysis of the fracture surface revealed that the failure behavior of the composite changed from ductile to brittle fracture with increasing iCNF loading. Optical transmittance of the composites was also investigated as a function of the iCNF loading.