Metal-oxide nanolaminate barrier coatings to enable large-scale manufacturing of sustainable flex packaging

The world is drowning in single-use-plastic waste. Compostable and recyclable alternatives to single-use flexible packaging exist but do not provide an adequate barrier to water-vapor and oxygen. We address this by using atmospheric-pressure spatial atomic layer deposition to apply Al 2 O 3 -ZnO nanolaminates on compostable polylactic acid (PLA) and recyclable polyethylene terephthalate (PET) films for flexible packaging. This industrially scalable coating is performed at 50 °C, preserving film integrity while enabling nanoscale control. The nanolaminate structure is found to enhance the bending resistance, improve the coating stability, and drastically reduce the water-vapor transmission rate (WVTR) and oxygen transmission rate (OTR). An optimized 8-stack Al 2 O 3 -ZnO nanolaminate that is ∼96 nm thick reduces the WVTR of PLA packaging film from ∼300 g m −2 ·24hr −1 to <0.5 g m −2 ·24hr −1 and its OTR from ∼1000 cm 3 m −2 ·24hr −1 to <10 cm 3 m −2 ·24hr −1 (both measured at 38 o C and 90 % relative humidity), making it ideal for packaging air-sensitive goods. When the 8-stack nanolaminate is laminated between two PET films to form a simple packaging structure and is subjected to the harshest industry-standard Gelbo flex durability testing, it retains a WVTR <2 g m −2 ·24hr −1 . These ultrathin coatings are well-positioned to meet recyclability and compostability standards, enabling a viable path to sustainable flex packaging. • Compostable and recyclable flex packaging provide a poor barrier to water vapor and oxygen. • Al 2 O 3 -ZnO nanolaminate coatings prevent water-vapor and oxygen transmission through PLA and PET. • The coatings are deposited via industry-scalable spatial atomic layer deposition at 50 °C. • A coated and laminated PET film maintains excellent barrier properties after Gelbo flex testing. • The coatings can enable widescale use of compostable and recyclable flex packaging.