The effect of cross-linking density on water vapor and oxygen permeability of hybrid UV cured nano coatings

Abstract

In this study, the effect of cross-linking density of organic contents, precursor ratio and proportion of inorganic to organic phases on water and oxygen permeability of sol-gel based hybrid UV cured coating on biaxially oriented polypropylene (BOPP) substrate was evaluated. Multi-functional acrylic monomers including, Isobornyl acrlate (IBOA), Tripropylene glycol diacrylate (TPGDA), Trimethylol propane triacrylate (TMPTA), Di-penta-erythritol hexa-acrlate (DPHA) and tri-functional aliphatic urethan acrylate oligomer were used as organic phase, while inorganic phase contained tetraethyl orthosilicate (TEOS) and 3-methacryloxy propyltrimethoxy silane (MEMO) precursors. A mixture technique utilized as designing the experimental processes. A high cross-linked hybrid enhanced the barrier property and reduced considerably both the water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) of uncoated BOPP from 88 ± 0.89, to 0.88 ± 0.05 (g / m2.day) and from 2010 ± 26–317 ± 11 (cm3 / m2.day), respectively. It was observed that in constant TEOS to MEMO ratio (I/O = 50), by altering the ratio of inorganic /organic from 20 to 80 water vapor depreciated from 3.9 ± 0.10 to 0.88 ± 0.05 g/ (m2.d). These results were in agreement with the presence of a dense network. Phase images of atomic force microscopy analysis showed a homogenous distribution of inorganic particles in the organic network. The presence of a high cross-linked organic phase can replace the presence of 30% of an inorganic phase in hybrid coatings. The correlation between WVTR and the multiplication of the surface energy (ε) in the cross-linking density (ʋ) has shown that increasing the diffusion coefficient had considerable influence on reduction of WVTR than increasing the solubility coefficient.