Comparison of Mechanical Reinforcement Effects of Cellulose Nanofibers and Montmorillonite in Starch Composite

Both cellulose nanofibers (CNF) and montmorillonites (MMT) are nanoscale reinforcement fillers that have shown reinforcing effects in polymer nanocomposites. CNFs belong to one-dimensional nanofibers while MMT is part of two-dimensional clay platelets, which show difference in shape, size, and composition. This study systematically compares their morphology and dispersion properties in a corn starch (CS) matrix, interactions with the matrix, and the resulting reinforcing effects on the CS matrix. Transparent CS/CNF and CS/MMT nanocomposites comprising up to 7 wt% nanofillers are obtained via solution casting. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Scanning Electron Microscope (SEM), and tensile testing, thermogravimetry analysis (TGA), moisture uptake (Mu), and light transmittance (Tr) are used to examine the above-mentioned properties of CS composites. It is found that the tensile properties, optical transparency, and water barrier properties of CS films are significantly improved whether adding a certain amount of CNF or MMT. However, the tensile strength increment of CS composites reinforced with CNF is slightly higher than that of MMT-reinforced CS composites due to higher aspect ratio of CNF. From the results, it can be concluded that CNF is highly compatible with starch and can reinforce the starch phase efficiently to prepare green nanocomposite films.