Carrier Systems for Cellulose Nanofibers in Hydrophobic Polymer Composites

Recent years have seen a sharp increase in interest around the world regarding cellulose nanocomposites. The number of publications including research papers and patents on the preparation of nanocomposites containing cellulose nanofibers has dramatically increased. One of the major challenges in cellulose nanocomposite applications is the lack of compatibility with hydrophobic polymer matrices. Cellulose nanofibers cannot simply be added to the polymer melt in thermal compounding processes because of the potential for agglomeration. To prevent cellulose nanofibrils from aggregating, and also to improve their dispersion in hydrophobic polymer matrices, modification of cellulose surfaces or use of a carrier system for cellulose nanofibrils is required. In this study, cellulose nanofiber suspensions were processed with novel carrier systems, using thermoplastic starch (TPS), functionalized TPS, polyvinyl alcohol (PVA) and poly-hydroxybutyrate (PHB) in an attempt to create compatibility between the cellulose nanofibril (CNF) suspension and hydrophobic polymer matrices including polyolefin matrices (polypropylene (PP), polyethylene (PE)) and a biodegradable polymer matrix (polylactic acid (PLA). Experimental cellulose nanocomposite process mixing using conventional thermoplastic processing techniques took place on a C.W. Brabender Prep Mixer® temperature controlled mixing head. Tensile, flexural and impact tests were used to evaluate the mechanical properties of the composites, and the composite densities were determined. Results indicate that CNF with carrier system-filled composites showed comparable or lower mechanical properties compared to control samples without the addition of compatibilizers. Several analytical tools were used to screen the composite materials including: scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and cone and plate rheometry to determine rheological behavior including shear rate and viscosity. It is believed that this research provides insight into potential applications of CNF-filled hydrophobic polymers. Possible applications for the composites studied in this research are packaging materials, construction materials and auto parts for interior applications