Surface modification of cellulose nanofibrils by maleated styrene block copolymer and their composite reinforcement application

Cellulose nanofibrils (CNFs) have been of great interest as reinforcing fillers because of their low density, high aspect ratio, and excellent mechanical strength properties. The advantages of CNFs, however, are often limited by their self-aggregation tendency and poor interfacial compatibility with hydrophobic polymer matrices. In this study, maleated styrene block copolymers were grafted on the surface of CNFs through esterification. The grafted polymer fraction of 25 wt% by gravimetric measurement was obtained. The evidence of grafting was also supported by changes in chemical functional groups and addition of the polymer thermal degradation step. A contact angle as high as 130° was observed on modified CNF film. The influences of modified CNFs on the surface morphology, thermal stability, and crystallinity were also evaluated and compared with those of neat CNFs. The reinforcing capability of CNFs as reinforcing fillers in the hydrophobic polymer matrix was assessed. The results also highlight the effect of improved compatibility between the surface modified CNF and polystyrene matrix to maintain optimum tensile strength at various filler concentrations.