Effect of ionizing radiation on the physicochemical and mechanical properties of commercial monolayer flexible plastics packaging materials

The effect of γ-radiation doses (5, 10, 30 kGy) on the mechanical properties, gas and water vapour permeability, infrared (IR) spectra, and overall migration into aqueous and alternative fatty food simulants of commercial monolayer flexible packaging films ethylene vinyl acetate (EVA), high-density polyethylene (HDPE), polystyrene (PS), bi-axially oriented polypropylene (BOPP), low-density polyethylene (LDPE) and Ionomer was studied. For comparison purposes, respective non-irradiated (control) films were also studied. The results showed that radiation doses of 5, 10 and 30 kGy did not induce any statistically significant changes in the permeability of all studied films to gases (oxygen and carbon dioxide) and water vapour. Likewise, IR spectra of all studied films showed no significant differences after all absorbed doses. The mechanical properties (tensile strength, percentage elongation at break and Young's modulus) of all studied films remained unaffected after absorbed doses of 5 and 10 kGy. In contrast, the tensile strength of HDPE, BOPP and Ionomer films irradiated at a dose of 30kGy decreased. In addition, the percentage elongation at break of LDPE and Ionomer films irradiated at a dose of 30 kGy decreased while Young's modulus of all samples remained unaffected. All mechanical properties of PS and EVA films remained unaffected after radiation at 30 kGy. Radiation (all absorbed doses) resulted in no statistically significant differences in overall migration values into distilled water for all studied films. For 3% aqueous acetic acid, absorbed doses of 5 and 10 kGy did not affect overall migration values of all investigated samples with the exception of the Ionomer film, for which the overall migration value decreased at 10 kGy. An absorbed dose of 30 kGy caused an increase in BOPP overall migration values and a decrease in Ionomer overall migration values. In contrast, a dose of 30 kGy induced no changes in overall migration values of EVA, HDPE, LDPE and PS films into the same simulant. There were no statistically significant differences in overall migration values of EVA, PS and LDPE films into iso-octane for all absorbed doses. In contrast, a dose of 30 kGy resulted in an increase in overall migration values of BOPP and a respective decrease in HDPE and Ionomer films.