Effect of chemical modifications and electron beam irradiation on properties of corn cob filled chitosan biocomposite films

Abstract

The chitosan (CS)/corn cob (CC) biocomposite films were prepared via solvent casting method. The effects of CC content, crosslinking agents such as glutaraldehyde (GLA), salicylaldehyde (SAL), epichlorohydrin (EP) and phthalic anhydride (PTH), and chemical modification of CC with acrylic acid (AA) on tensile properties, thermogravimetric analysis (TGA), morphology study, gel fraction and biodegradation properties of CS/CC biocomposite films were investigated. The effect of electron beam irradiation on properties of unmodified and modified CS/CC biocomposite films were also studied. The results indicated that the tensile strength, elongation at break, Tonset, Tdmax and residue of unmodified CS/CC biocomposite films decreased as increases of CC content. However, the modulus of elasticity, gel fraction, weight loss of enzymatic and soil biodegradation of unmodified biocomposite films increased with increasing CC content. The morphology of unmodified biocomposite films showed poor CC dispersion and interfacial interaction in CS matrix. The effect of different crosslinking agents such as GLA, SAL, EP and PTH in biocomposite films have higher tensile strength, modulus of elasticity, Tonset, Tdmax, and residue in comparison with unmodified biocomposite films. The gel fraction of all modified biocomposite films higher than unmodified biocomposite films. Whereas, the modified biocomposite films exhibited decrement in elongation at break and weight loss of both enzymatic and soil biodegradation. The treated CC with AA improved the tensile strength, elongation at break, Tdmax and char residue of biocomposite films, but reduced the modulus of elasticity and weight loss in enzymatic and soil biodegradation of biocomposite films. The gel fraction of treated biocomposite films with AA was slightly improved. The SEM micrograph of all modified biocomposite films showed better filler dispersion and adhesion in CS matrix. The tensile strength, modulus of elasticity and Tonset, Tdmax of irradiated modified CS/CC biocomposite films with SAL was higher than unirradiated biocomposite films. Meanwhile, the residue of irradiated modified biocomposite films with SAL reduced when the temperature up to 500 oC. The weight loss of both enzymatic and soil biodegradation of irradiated biocomposite films were lower than unirradiated biocomposite films. The morphology of irradiated modified biocomposite films indicated brittle surface. The FTIR spectra of all modified biocomposite films showed the changes in functional groups in all modified biocomposite films. From all chemical modifications, the irradiated modified CS/CC bicomposite films with SAL showed the highest tensile strength, modulus of elasticity, gel fraction, Tonset and Tdmax. The elongation at break and weight loss of enzymatic and soil biodegradation of irradiated modified biocomposite films with SAL were the lowest compared to others modified biocomposite films.