Study the factors affecting water vapor barrier properties of organic–inorganic hybrid coatings

Abstract

Water vapor barrier materials are crucial importance in the packaging industry. Herein, a series of organic–inorganic hybrid coatings are successfully deposited onto polyethylene terephthalate (PET) film through a facile casting method. These coatings impart PET film with enhanced water vapor barrier properties. Particularly, the influencing factors for the water vapor barrier property are systematically investigated in terms of polymers, inorganic fillers and environmental pH level. The results demonstrate that the hybrid coatings comprising ethylene-vinyl alcohol copolymer resin (AQ4104) and inorganic filler with peelable structure, including micas (ME-100 and NTS) and sodium montmorillonite (K–F) significantly reduce the water vapor transmittance ratio (WVTR) of PET film. The WVTR of PET film coated with ME-100/AQ4104 hybrid is 0.7 g·m −2 /day, which is reduced by 80% than that of uncoated PET film. Also, the composite coatings comprising polyurethane resin (WPB-341) and NTS greatly reduce the WVTR of PET film to 1.0 g·m −2 /day at 20 wt% NTS content. The inorganic fillers with both small sheet diameter and peelable sheet structure are greatly advantageous for the water vapor barrier property of hybrid coatings. Additionally, the adhesion tests show that these composite coatings possess great adhesion strength, especially for NTS/WPB-341 composite coating of 4.92 N/cm. Moreover, when the environmental pH is adjusted from original alkaline to acidic, the WVTR of PET film coated with AQ4104-based composite coatings is changed, indicating the pH-dependent water vapor barrier ability. This research may provide some reference significance for the simple, low-cost and easy large-scale production of high-performance water vapor barrier coatings for packaging applications.