Effect of ionizing irradiation techniques on biodegradable packaging materials

EFFECT OF IONIZING IRRADIATION TECHNIQUES ON BIODEGRADABLE PACKAGING MATERIALS By Patnarin Benyathiar Ionizing irradiation has developed as a package sterilization technology, which may be an alternative to other current sterilization methods. This is because of its efficiency in reducing foodborne pathogen levels without leaving residual chemicals. In the use of irradiation sterilization either prior to or after filling, the packaging material is directly exposed to radiation. Irradiation has been known to alter the properties of polymeric packaging materials. The exposure causes changes in material properties and may produce by-products. Biodegradable packaging materials have received more attention in the current marketplace in order to reduce the packaging waste in the landfill. Polylactic acid (PLA) and cellophane, derived from renewable sources, have become well-known as green packaging materials in today’s markets for foods and pharmaceuticals. However, knowledge about the effects of ionizing radiation on these biodegradable materials is still scarce and. In this study, the effects of three common irradiation types (X-ray, gamma, and electron beam irradiation) on properties of PLA and cellophane were studied. The physical, chemical, thermal, mechanical, and barrier properties of irradiated samples at absorbed doses of 1 to 30 kGy after storage times of up to 9 months were determined and compared to non-irradiated samples. The effect of irradiation on the migration from PLA and cellophane films into liquid food simulants was also investigated. Furthermore, the biodegradation of irradiated biomaterials also was investigated. The physical, chemical, thermal, and mechanical properties were affected by Xray, gamma and electron beam irradiation as a function of irradiation dose and storage time. A significant decrease in molecular weight of PLA indicated the degradation of the polymer by irradiation. Irradiation induced a change in polymer properties due to the predominance of chain scission. Ionizing radiation decreased the water vapor permeability of PLA and nitrocellulose-coated cellophane, while PVdC-coated cellophane was not sensitive to irradiation. In the study of food and packaging interaction, overall migration of PLA into food simulants increased with absorbed dose. but remained below the limit set by EU regulations. Overall migration from nitrocellulose-coated cellophane and PVdC-coated cellophane was higher in 95% ethanol. Biodegradation of PLA was influenced by ionizing radiation. Aging irradiated PLA had some potential to increase the biodegradation rate. Non-irradiated and irradiated PLA films can be considered as biodegradable plastics with greater than 60% mineralization as required by ASTM D6400 and ISO 14855-1. The results of the biodegradation study showed that the non-irradiated and irradiated uncoated cellophane qualified as a biodegradable plastic while nitrocellulose-coated cellophane and PVdCcoated cellophane films with and without irradiation treatments showed potential to be considered biodegradable. The results from this dissertation indicated that commercial PLA and three cellophane films were suitable for packaging applications after irradiation treatment.