Eco-friendly bio-based composites of cassava starch and natural rubber compatibilized with nanoclays

Biocomposite films from cassava starch (CS) blended with natural rubber (NR) compatibilized with nanoclay were prepared. Three types of nanoclays, that is, montmorillonite (MMT), kaolinite (KAO) and intercalated kaolinite (DKAO) were used with various content of 2, 4, 6 and 8 wt%, respectively. The mechanical property, water vapor transmission and water solubility of CS/NR composite films were investigated and the interaction of constituents in the CS/NR composites was also characterized by using x-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscope and dynamic mechanical analysis. The results revealed that the addition of clays considerably improved both the tensile property and water resistance over the pristine starch and CS/NR film. Biocomposite film with 4 wt% of MMT exhibited minimum water vapor transmission and solubility in water content. The tensile strength of CS/NR composites significantly increased while the elongation at break of composites tended to decrease with the increasing nanoclay content. Both mechanical and physical properties were attributed to strong interaction by forming the intercalated structure of MMT and exfoliated structure of DKAO within biocomposites while less interaction was obtained in the case of KAO. The compatibilizing effect of nanoclay in CS/NR composites was also indicated that the glass transition temperature (T-g) of NR or CS-glycerol phase shifted to higher T-g than that of CS/NR film.