The effects of γ-irradiation on compositional changes in plastic packaging films

Sterilization of packaging materials for pharmaceutical or food products with ionizing irradiation can cause chemical and physical changes in polymer materials. The effects of γ-irradiation on the formation of solvent extractable radiolysis products of six flexible packaging materials for foodstuffs and/or pharmaceutical applications were studied after treatment in a 60Co-irradiation plant. The polymer materials polyethylene, polypropylene, poly(ethylene terephthalate), polyamide, polystyrene and poly(vinyl chloride) were investigated after treating with an irradiation dose of 44 kGy. The compositional changes in solvent extractable radiolysis products of each packaging material were quantified. In most cases the radiolysis products formed could be identified using GC/MS. The polyolefine materials (PE and PP) showed an increase of low volatile compounds after irradiation due to an oxidative decomposition of the polymer and typical polymer substances like oligomers and additives. Other packaging materials such as PET, PA and PS did not significantly change their amount of solvent extractable compounds after irradiation with 44 kGy. The PVC packaging material used in this study was not resistant to irradiation treatment at all. Because of the release of HCl during irradiation a large amount of volatile substances could be extracted from the PVC sheet. For consumer protection and also to meet general food packaging legislative requirements for irradiated packaging materials, it is necessary to evaluate the compositional changes in the polymers during irradiation, especially for irradiated polyolefines and PVC. Most attention should be paid to low volatile radiolysis products which are the most likely to migrate into a foodstuff or a pharmaceutical product. Copyright © 1999 John Wiley & Sons, Ltd.