Migration models used as tools in calculating additive and contaminant migration from food contact materials are designed conservatively for regulatory compliance testing to provide a safety margin for consumers. The generally recognized Piringer diffusion model requires a polymer-specific parameter, AP, to describe the basic diffusion behavior of a polymer in relation to its migrants. Ethylene vinyl alcohol (EVOH) is a random copolymer of ethylene and vinyl alcohol used as a high-oxygen barrier within multilayer flexible packaging. However, AP values for EVOH films of any ethylene content are not currently available. EVOH monolayer films of two ethylene contents, 44 mol% and 32 mol%, were studied using toluene as a surrogate migrant. Toluene has been used in solvent-based printing ink formulations on the outer layers of food packaging. Diffusion coefficients (DP), permeability coefficients, and solubility coefficients of toluene were determined by an isostatic permeation method at 90 °C, 100 °C, 110 °C, and 121°C. Results showed that higher ethylene content in EVOH 44 mol% film allowed increased migrant mobility within the polymer due to its lower Tg (53 °C) and closer proximity to its Tm (165 °C) than EVOH 32 mol%. DP values for EVOH 44 mol% were determined in the range of 1.3 × 10-10 to 1.9 × 10-9 cm2/s, while DP values for EVOH 32 mol% were slower by approximately one order of magnitude. The activation energies of diffusion (EA) for toluene in EVOH 44 mol% and EVOH 32 mol% films determined from the Arrhenius plots of the experimental DP values were 100.9 kJ/mol and 130.3 kJ/mol, respectively. Higher EA values result in lower diffusion coefficients at a specific temperature. Mean AP values estimated for EVOH 44 mol% and EVOH 32 mol% were -0.4 and -1.9, respectively. Higher AP values lead to increased DP values of migrants in the polymer.

Effect of ethylene content in EVOH films on activation energies of diffusion of organic migrants and polymer modeling parameters

2019 Fall National Meeting

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