Abstract: Montmorillonite（MMT）was surface-treated with γ-glycidoxypropyltrimethoxysilane (KH560) as a modifier, and then the surface-modified MMT was blended with vinyl acetate ethylene copolymer (VAE) emulsion to prepare a type of nanocomposite barrier coating. The structure of pristine MMT and surface-modified MMT were characterized by FTIR and XRD, and the microstructure, thermal stability, mechanical and barrier properties of MMT/VAE nanocomposite coatings were further evaluated by SEM, XRD, TG, DSC, the penetration experiments of water vapor and oxygen, and tensile experiments. The results indicated that KH560 was successfully grafted onto the surface of MMT, thus resulting in an increase of interlaminar spacing of MMT from 1.210 nm to 1.447 nm. The modified MMT was uniformly distributed in the VAE matrix, and the interlaminar spacing of MMT was further improved to 2.758 nm. The thermal stability of the nanocomposite coatings was also improved with an increase of MMT. After the PET thin film was coated with the nanocomposite coatings containing 50 wt % of surface-modified MMT, the water vapor and oxygen transmission rates of the thin film decreased by 81.79 % and 95.3 % respectively, and their yield strength increased by 52.68 %. Moreover, the thin films achieved an increase of elastic modulus by 74.16 % for the nanocomposite coatings containing 30 wt % of surface-modified MMT.

Key words: γ-glycidoxypropy ltrimethoxysilane, montmorillonite, vinyl acetate-ethylene copolymer emulsion; nanocomposite barrier coating