Influence of uniaxial orientation on oxygen barrier properties of polyethylene films

The transition from traditional materials like glass and metal to plastic films in food packaging has been driven by the latter's flexibility, versatility, and lightweight nature. However, challenges related to the recycling of multi-layered, multi-material flexible packaging have emerged, prompting interest in mono-material solutions for improved recycling and sustainability. Polyethylene (PE), a widely used polymer in flexible packaging, offers various structural and functional properties but faces issues with high oxygen permeability. This study investigates the potential of uniaxial orientation or machine direction orientation (MDO) to enhance the oxygen barrier property of PE films. Oxygen barrier properties were evaluated for blown and MDO films of varying resin densities, with the results correlating structural changes during stretching with improved barrier performance at a certain resin and process parameters. The findings demonstrated that uniaxial orientation or MDO operation has the potential to enhance the oxygen barrier of PE films, depending on resin type and processing conditions, primarily through enhanced crystallinity and microstructural orientation. • MDO operation improved overall crystallinity of PE films. • Higher-density MDO-PE films improved oxygen barrier via crystallinity and microstructural orientation. • Lower-density MDO-PE films showed higher permeability from limited microstructural orientation. • PE resin density optimization at fixed MDO parameters is critical for oxygen barrier performance.