Abstract
In this study oxygen permeability in dispersion barriers produced from poly(vinyl alcohol) (PVOH) and kaolin clay blends coated onto polymeric supports was investigated. To determine the oxygen permeability, two measurement methods were used: the oxygen transmission rate (OTR) and the ambient oxygen ingress rate (AOIR). It was found that with increasing kaolin content the oxygen permeability increased, up to about 5wt% kaolin, whereafter the oxygen permeability decreased, as was expected. The increased (>5%) kaolin loading lowered the diffusion because of an increased tortuosity. Structural information about the dispersion-barrier coatings, such as kaolin orientation and polymer crystallinity, was obtained from Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Kaolin orientation was influenced by the drying temperature, the thickness of the samples, and the kaolin concentration. The polymer crystallinity increased in thicker samples. The drying temperature did not show any clear effect on the crystallinity of thin samples, while for the thicker barriers, combined with a kaolin concentration lower than 20wt%, a higher crystallinity was achieved at lower drying temperatures. This study demonstrates the strong influence of chemical and physical structures on the permeability of the investigated coatings.
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