Carboxymethyl cellulose film modification through surface photo-crosslinking and chemical crosslinking for food packaging applications. (December 2016) - Shahbazi, Mahdiyar
Abstract: A comparative study between the combined effects of UV irradiation/sodium benzoate and glutaraldehyde vapor/gelatin on carboxymethyl cellulose (CMC) film with low degrees of substitution was performed. The kinetics of the surface photo-crosslinking and chemical crosslinking treatments were evaluated through determination of the film fraction and swelling rate in the crosslinked CMC networks. It was found that sodium benzoate and gelatin concentrations were dominant factors compared with UV irradiation and glutaraldehyde vapor induced times. The results of surface hydrophobicity, water barrier and mechanical properties were found to be a function of both treatments, among which photo-crosslinking treatment was more effective than the chemical crosslinking process. The pronounced peaks of CMC were disappeared in the fingerprint region after both crosslinking reactions. The cold-crystallization exothermic peak of CMC shifted to the lower temperature after the crosslinking treatments, indicating that more decrease belonged to the photo-crosslinked film. X-ray diffraction pattern of the modified films revealed the emergence of new pronounced peaks, coinciding with an increase in the CMC crystallinity. Many micro-cracks were recognized on the neat CMC surface, while the crosslinking treatments eliminated the cracks. Finally, the conformity of the crosslinked films with the actual food regulations on the biodegradable materials was verified by cytotoxicity test to study the possibility of utilizing in the food packaging sector. Both crosslinked films did not show any evidence of the cytotoxic effects since it could not increase the cytoplasmic lactate dehydrogenase release from L-929 fibroblast cells in contact with the films. Graphical abstract: Highlights: CMC films were modified through UV induced photo-crosslinking and chemical crosslinking. Photo-crosslinking and chemical crosslinking treatments increased water resistance and water hydrophobicity of CMC film. Tensile strength and water barrier property of chemically crosslinked CMC film was lower than photo-crosslinked film. Fast crystallization occurred after modifying CMC by photo-crosslinking and chemical crosslinking. Crystallinity degree of both crosslinked films was increased.