THE MIGRATION BEHAVIOUR OF MODEL PLASTICS ADDITIVES FROM POLYAMIDE COATINGS IN RELATION TO THEIR DONOR-ACCEPTOR COMPLEX FORMATION (FOOD, ANTI-OXIDANTS, PACKAGING)

The work presented in this text looks into the increasing problem of the migration of additives, necessary for the production of plastic packaging materials into foodstuffs and their simulants. It can be seen that over the years much work has already been undertaken in order to obtain an understanding of the causes of migration. Also the degree of migration for a multitude of additives from a variety of plastics has been observed. Furthermore, mathematical models representing the rates of migration for various classes of migration have been prepared and generally agreed. Therefore, the work described here details the possible use of the formation of charge transfer complexes as being a means of preventing the occurrence of migration or at least a way in which the rate of migration can be slowed down sufficiently so that the additive is no longer a health problem. The charge transfer complex is formed between an electron rich centre in the polymer and an electron deficient additive. In the systems studied here the electron rich centre was incorporated in a polyamide whilst fluoranil and TCNQ were taken to be model plastics additives. A common antioxidant, BHT, was taken as a standard since this was of similar molecular size and weight to the two model additives. Standardised test conditions of 10 days at 40(DEGREES)C and 65% relative humidity were employed throughout the experimental period in which distilled water was used as the simulant. The results showed that whilst an appreciable amount of the BHT was observed to have migrated the degree of migration of the two model additives was not measurable by the TLC method employed even though the level of detection for fluoranil was equivalent to that of BHT whilst that for TCNQ was at least an order of magnitude lower. The model systems were then studied in solution by a spectrophotometric technique using the methods of analysis developed by Benesi and Hildebrand and Foster.