Improvement of oxygen barrier of oriented polypropylene films coated by gravure ink-containing nanoclays

The feasibility of a gravure ink-containing nanoclays as an alternative oxygen (O₂) barrier material to oriented polypropylene (OPP) film was investigated. The gravure ink was effectively dispersed through the clay using an ultrasonic homogenizer. Barrier properties of OPP films coated by the gravure ink-containing nanoclays were evaluated with respect to dispersion time, clay content, and different types of nanoclays (Cloisite Na, Cloisite 25A, and Cloisite 30B). Barrier and morphology properties of the OPP films were tested by measuring selected film properties such as O₂ transmission rate (OTR), and water vapor transmission rate, and by field emission scanning electron microscopy, X-ray diffraction (XRD), and transmission electron microscopy (TEM). OTR of control OPP film coated solely with gravure ink was 1653 cm³ m^-2 day, while use of OPP films coated by the three different types of gravure ink-containing nanoclays (nanoclay content: 1% w/w) reduced OTR by 12-37%. OTR values measured using the gravure ink-containing modified montmorillonite (Cloisite 25A and Cloisite 30B) were markedly lower than measured by pristine gravure ink-containing unmodified montmorillonite (Cloisite Na⁺). On the other hand, no remarkable differences were evident in the water vapor barrier performance of control OPP film and gravure ink-containing nanoclay-coated OPP film. As nanoclay content and dispersion time increased, OTR values of the OPP films coated by gravure ink-containing nanoclays decreased. And the TEM and XRD observation indicated that intercalated and exfoliated types were generated.