Preparation and Characterization of Corn Starch Nanocrystal Reinforced Natural Rubber Nanocomposites via Co-coagulation Process

Corn starch nanocrystals were found to serve as an effective reinforcing agent for natural rubber (NR). Starch nanocrystals were obtained by the sulfuric acid hydrolysis of starch granules. After mixing the latex and the starch nanocrystals, the resulting aqueous suspension was made into coagulum and then it is mixed with the dry NR and cross linking agents, in two roll mill followed by compression molding. The composite samples were prepared by varying filler loadings, using a colloidal suspension of starch nanocrystals and NR latex and dry rubber. The morphology of the nanocomposites prepared was analyzed by Field Emission Scanning Electron Microscopy (FESEM) and FESEM analysis revealed the size and shape of the crystal and their homogeneity dispersion in the composites. The crystallinity of the nanocomposites was studied using XRD analysis which indicated an overall increase in crystallinity with increased in filler content. The mechanical properties of the nanocomposites such as stress-strain behaviour, tensile strength, tensile modulus and elongation at break were measured according to ASTM standards. The tensile strength and modulus of the composites were found to improve tremendously with increasing nanocrystal content. This dramatic increase observed in the modulus and the tensile strength can be attributed to the formation of starch nanocrystal network. This network immobilizes the polymer chains leading to an increase in the modulus and other mechanical properties. The DMA studies of the composites were carried out and it reveals the effective reinforcing mechanism of starch nanocrystal on NR matrix.