Effect of crosslinking agent on the physical and mechanical properties of a composite foam based on cassava starch and coconut residue fiber

Abstract

Abstract A biodegradable composite foam made from cassava starch mixed with coconut residue fiber (CRF) was first successfully prepared using a conventional compression molding technique. Cassava starch is an agricultural economy product of Thailand that is produced in high production each year. CRF is a waste product left over after the removal of coconut milk from coconut fiber. CRF is lightweight and high porosity, which is suitable for preparing into the composite foam. The effect of loading of boric acid (crosslinking agent) and CRF on the morphology (SEM), functional group (FT-IR), mechanical properties (tensile strength, modulus, %elongation by tensile testing), thermal property (TGA) and biodegradation in soil of the composite foam were investigated. The samples were compression molded at 180 oC for 9 min. The foam comprised of 70 %w/w cassava starch and 30%w/w poly(vinyl alcohol) was used with different loading of boric acid (0, 0.1, 0.3 and 0.5 %w/w) along with various amounts of coconut residue fiber (0, 2, 4, 6 and 8% w/w). When using higher loading of crosslinking agent, the density of composite foam decreased, while tensile strength, hardness and water absorption increased. In addition, the stronger cell wall and more porosity of the composite foam were found with higher contents of crosslinking agent. This enhances the biodegradation of the composite foam in soil. A good distribution of the CRF into the cassava starch matrix was also observed, which promoted the porosity of this composite foam. Using boric acid as a crosslinking agent for this composite foam promoted the porosity and biodegradation in soil. This novel composite has the potential to be used for shockproof packaging that is fully biodegradable, environmentally friendly and non-toxic materials.