Migrants, Migration oligomers

Migration of unreacted polyol components through the polyethylene for the polyether-based laminate was observed. Although an excess of isocyanate was present, diffusion of polyol components into the polyethylene prior to reaction with isocyanate was postulated to explain the migration. Cyclic oligomers from the polyol starting materials were identified as the main migrants from the polyester-based adhesive. 

In Japan, specific legislation for migration from PLA was published in October 2007. It states a limit for total lactic acid of <30(ig/mL of water after alkaline decomposition of the simulant [14]. During this treatment, migrants like LA and PLA oligomers are hydrolyzed and accounted as lactic acid. 

Both studies by Conn et al. [8] and Mutsuga et al. [19] included hydrolysis experiments in order to quantify all the migrants as lactic acid. Stability of lactic acid and oligomers and the effect of temperature and time on migration were also determined. In both the studies, migration solutions were saponified with sodium hydroxide before quantification by liquid chromatography. 

It can be seen that the GC-MS method would be likely to fail to properly detect potential migratable species such as low volatility monomers, higher MW oligomers and possibly miss out on certain compounds that decomposed during the analysis. These considerations explain why Lin and co-workers [6] utilised the non-destructive LC-MS method for detection and identification of the potential migrants from UV/EB curable, acrylate type formulations. 

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