Prediction of permeability of laminate film; New methods for ultra-thin layers and systems with solute-concentration-dependent diffusivity

Two numerical methods have been developed for the prediction of gas/vapour transmission rates in multilayer laminate films consisting of different pol ymers with extensive variations in relative thicknesses. The methods develo ped allow the use of different spatial step lengths for the different layer s. The methods have been applied to experimental oxygen transmission rates through laminates based on low-density polyethylene and poly(ethylene terep hthalate) and it was found that the predictions agreed with the experimenta l results within the experimental Error limits. The methods were also used to predict the water vapour transmission rates for a three-layer laminate o f low-density polyethylene and polyamide-6. Since water vapour diffusivity in polyamide-6 is a function of the water concentration, different and some times complex results were obtained depending on the location of the polyam ide-6 layer in the laminate. Calculations showed that fire only way to pred ict the optimum positions of different layers, in order to minimize the pen etrant transmission rate through a laminate when the penetrant interacts wi th the material, is by rigorous sir simulations using these or similar meth ods. Copyright (C) 1999 John Wiley & Sons, Ltd.