Abstract
Crosslinking is a common practice to improve the barrier properties of polymers. In this study, Montmorillonite (MMT) was used with Polyvinyl alcohol (PVA) to deposit nanocomposite coatings which were crosslinked with glyoxal (Gly) by Layer by Layer (LbL) on a PET substrate. Two crosslinking conditions were studied, under mild condition and with an acidic environment. Mild condition was useful to identify the reversibility steps and the optimum crosslinking times while the acidic environment was essential to investigate the crosslinking mechanism, by determining the permeability for different crosslinking times. PVA and PVA-MMT coatings showed a strong correlation between the permeability coefficients for different crosslinking times and the FTIR results.
Highlights
Barrier materials are in constant demand for a wide variety of applications, especially for food packaging which has a considerable growth of the flexible packaging market
Montmorillonite (MMT) was used with Polyvinyl alcohol (PVA) to deposit nanocomposite coatings which were crosslinked with glyoxal (Gly) by Layer by Layer (LbL) on a polyethylene terephthalate (PET) substrate
For aldehydes crosslinkers the crosslinking mechanism with polymers containing hydroxyl groups in their structure, e.g. PVA, is based on two reactions occurring in an acidic environment
Summary
Barrier materials are in constant demand for a wide variety of applications, especially for food packaging which has a considerable growth of the flexible packaging market. Metallic and silicon oxide coatings are extensively used for high barrier packaging Some affordable materials like clay, improves considerably the polymer properties even with adding low amounts, due to its high aspect ratio [4]. For polymers with hydroxyl and amine functional groups, dialdehydes in particular are widely used Their remarkable reactivity results in a high crosslinking density, reducing considerably the free volume in the film. To the best of our knowledge, this is the first thorough study of the variation of permeability with crosslinking time, the tracking of the acetal reaction reversibility and the correlation of permeability and FTIR absorption intensity for LbL coatings.
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