Study of the oxygen barrier properties of PET via ultrasonic spray coating of ZnO nanoparticles

Abstract

Polyethylene terephthalate (PET) has been widely used as packaging material due to its versatility, durability and low cost. It also owns good gas barrier properties.Various processing methods such as physical vapor deposition and chemical vapor deposition with nanoparticles have been used to optimize the barrier properties of different polymers. In this study, ultrasonic spray coating a wet-chemical deposition method is employed to deposit zinc oxide nanoparticles (ZnO NPs) on a commercial PET film in order to enhance its oxygen gas barrier properties. To achieve a uniform coated layer of ZnO NPs on the PET substrate, the ink concentration and spray coating parameters were both optimized. An ink with 2.5 wt.% ZnO NPs was prepared in 1 wt.% polyvinyl alcohol (PVA), isopropanol (IPA) and de-ionized (DI) water. The spray coating process was optimized for following parameters: path speed (10 mm/sec), pump flow rate (0.1 ml/min), generator power (2.5 watts),nozzle to substrate distance (75 mm), hot plate temperature (30 °C) and amount of coated layers (50x).Scanning electron microscopy (SEM) results showed a uniform coated layer of ZnO NPs on the PET substrate. Oxygen transmission rate (OTR) tests were performed at 23 °C and 0% relative humidity (RH). This study demonstrates that the OTR value of 50x ZnO NPs coated PET substrate is decreased.