Diffusion modeling in polymer–clay nanocomposites for food packaging applications through finite element analysis of TEM images

Abstract

Nanocomposites are novel materials increasingly used in the food packaging industry because of their enhanced properties with respect to unfilled polymers, more specifically in active packaging because of their great potential to retain and control active molecules release into the preserved food. The estimation of the improvement achieved in barrier or retention properties is usually performed through the calculation of relative diffusivity, through application of theoretical models. However, their results are disparate and quite inaccurate when working with nanocomposites with low values of volume fraction and aspect ratio of particles. The method presented in this work is based on the mathematical modeling and simulation of diffusion processes, and, unlike the previous models, it only requires as input some TEM micrographs of actual polymer nanocomposites. By subjecting such micrographs to image and finite element analysis the model can yield accurate values of relative diffusivity. EVOH-29 and zein matrices with 1 or 2% of bentonite nanoparticles were employed to validate the model, with average reductions from 3.8 to 12.2% in their solute diffusivities. In spite of possible size effects of diffusing molecules, not considered in the model, values were in agreement with experimental data obtained from permeability measurements, validating the propounded method.