Influence of processing conditions on properties of poly (vinyl acetate)/ cellulose nanocrystals nanocomposites

We investigated how different processing methods affect the morphology and mechanical properties of nanocomposites made from poly(vinyl acetate) (PVAc) and cellulose nanocrystals (CNCs). Homogeneously mixed reference PVAc/CNC nanocomposites of various compositions were first prepared by solution casting. These materials were post-processed by mixing in a roller blade mixer (RBM) or a twin-screw extruder (TSE) and subsequent compression molding. Transmission electron microscopy was used to elucidate the dispersion and size distribution of the CNCs and these data were correlated with the materials' mechanical properties. While RBM processed composites are virtually indistinguishable from the solution-cast reference materials, TSE processing led to mechanical degradation of the CNCs and resulted materials with inferior mechanical properties. Direct RBM mixing of PVAc and CNCs was also explored. This process afforded materials that are much stiffer than the neat matrix, but did not reach the levels of the reference series.