Oligomers in polyester food contact materials : Identification and migration studies

Oligomers are unavoidably formed during the production of polymers and evoke attention as potential migrants, from a qualitative and quantitative point of view. Many monomers are authorised to be used for food contact polyesters since long but only for two recently authorised food contact polymers a specific total oligomer migration limit was assigned by the European Union. Generally, mass spectrometry coupled to liquid chromatography has been shown to represent the analytical approach of choice for identification while UV-detection is often used for quantification purposes. In this thesis four different polyesters –PET, PEF, PEN and PBT – were investigated with regard to their oligomer content. The majority of the identified oligomers was shown to comprise a cyclic structure. Small amounts of linear oligomers were found in PEF, PBT and PEN material. The total oligomer concentration in each of the four materials was below 1%. Theoretical model approaches are a fast and easy way to estimate the oligomer migration. For PET oligomers the Welle approach was shown to be suitable to determine their migration. Also it was shown that for cyclic PBT oligomers the Welle model might be applicable, but underestimates the migration of the oligomers to some extent whereas the Piringer model overestimates the migration of the cyclic oligomers. Since there are many types of (co)polyesters that are authorised via the used (co)monomers for food contact materials, each of them deserves separate investigation with regard to its oligomer content. Furthermore, the applicability of the available migration models needs to be examined for newly developed polyesters to study the diffusion in and migration of oligomers from these different materials.