Led by increasing demand from the food industry and its consumers, the use of flexible packaging solutions is on the rise. The global flexible packaging market is projected to surpass $300 billion by 2030, according to data from Statista. Pouches, which are ideal for meals and snacks on the go, represent the fastest growing segment, but the popularity of these robust and portable packages poses a challenge for companies looking to improve the sustainability of their packaging. 

Compared to rigid packaging, a pouch package can reduce the weight of the packaging and can increase the number of packages transported per truckload. However, pouches and other packages that utilize mixed material films are difficult or impossible to recycle with existing technology and infrastructure. As Extended Producer Responsibility (EPR) legislation gains traction in the United States and around the world, companies will be required to incorporate recycled content into their packaging materials and design packaging that can be recycled. 

Mono-material packaging is easier to incorporate in recycling streams, but designing high performance packaging with a single material has posed difficulties for many types of pouches, wrappers, and bags that require a specific combination of characteristics to keep food fresh and prevent product damage. 

The latest advances in high-density polyethylene (HDPE) resin and production technology are making it possible to design all-PE structures for even the most demanding applications. Oriented PE films have enhanced performance properties that can meet the needs of pouches and flexible packaging formats that have traditionally used multi-material constructions to extend shelf life. 

Performance Considerations

Many flexible packaging films rely on layers of different materials to achieve the necessary performance requirements, which often includes a barrier layer, sealing layer, and a printing substrate. Certain layers must also be compatible with various coating and lamination processes. In terms of production, films must be able to run on high-speed packaging equipment and demonstrate heat resistance during sealing and converting. 

Traditional low-density and linear low-density PE (LDPE, LLPE) films lack the heat resistance and stiffness to fulfill these requirements, but orientation of HDPE allows for property improvements that enable high performance, all-PE packaging designs.

Benefits of Oriented Films

Orientation is used to enhance the barrier, mechanical, and optical properties of PE films, surpassing the capabilities of blown or cast films. The process involves changing the molecular alignment of polymer chains by heating the film and then stretching it in one or more directions. Machine direction orientation (MDO) stretches a film in one direction, and biaxially oriented (BO) films are stretched in both the machine and transverse directions. 

Oriented PE films have the stiffness required for printing processes and for use in stand-up pouches (SUPs), and they can be laminated with PE sealant resins to create a single-material sealant web. With their improved toughness and puncture resistance, oriented films also allow for the downgauging of packaging films, resulting in less material usage and lighter weight structures. These performance benefits mean that oriented PE films can be used to replace biaxially oriented polypropylene (BOPP) and PET (BOPET) in multilayer films. 

Customized MDO-HDPE Structures

MDO-HDPE films offer flexible design options with a broad orientation window and a variety of gauge possibilities. These films combine heat resistance with minimal film shrinkage, allowing them to withstand conversion and coating processes. Produced on co-extrusion blown film lines, MDO-HDPE can be customized for small runs with specific requirements and can accommodate custom laminates such as an HDPE print web with a moisture barrier all-PE co-extruded film. MDO films are ideal for food packaging applications, offering a very low haze and very high gloss finish as well as the appropriate stiffness to maintain registration during printing. MDO-HDPE is a cost-effective solution for converters fulfilling lower volume orders.

Economy of Scale with BOPE-HD Films

BOPE-HD film technology is rapidly changing as material innovations open the door to new possibilities. Resin supplier NOVA Chemicals has developed the first HDPE resin for the biaxial orientation process, providing an alternative to BOPE-LLD, which lacks the necessary heat resistance and stiffness for many packaging designs. Working with equipment manufacturer Brückner Maschinenbau, the new resin was specifically designed to match the viscosity of polypropylene (PP) and run on commercial tenter frame lines to help speed market adoption. 

BOPE-HD films are produced on large-scale equipment with high output capacities. The high-density resin has been tested successfully on premade pouch lines and horizontal form-fill-seal (HFFS) flow wrapper lines. BOPE-HD films have a higher abuse resistance than MDO films, making them well suited for large packages and liquid packaging. They also provide design versatility, with options for high clarity and matte films available. BOPE-HD films can be paired with PE sealant webs to create mono-material pouches and pillow packs.

Next Steps for the Industry

Mono-material packaging designs contribute to higher quality recycled feedstock, which in turn can potentially strengthen the availability of post-consumer recycled (PCR) materials that can be reused in high performance applications. Continued investment in both packaging redesign and recycling infrastructure is essential to support the growth of flexible packaging that is ready to be recycled and made from recycled materials. 

Oriented PE films are important building blocks in the foundation of recyclable packaging. MDO film production is more widely used today, but the scalability of BOPE films will be needed to accelerate the global transition to recyclable packaging. Suppliers and converters should work together to explore the new options available with oriented PE films and how the latest technologies can meet brand owner needs for more sustainable packaging designs.