Challenge
Flexible primary packaging today is often created from composite laminates, typically comprising two layers — a PE film sealant together with a PA/PET substrate. These multimaterial structures have the advantages of good sealing, high oxygen barrier capabilities as well as excellent stiffness. However, they can be challenging to recycle using existing processes as often the different layers first need to be detached for further treatment of the materials separately.
A potential alternative is a mono-material structure created with PE films, i.e. replacing the PA/PET substrate with a PE substrate. However, it is important to ensure that the mono-material structure maintains the desired properties comparable to those of multi-materials such as processability, printability, heat sealability, stiffness, to name a few. There is an increasing demand for monomaterial, recyclable* flexible films in many food packaging applications, such as stand-up pouches and flow wrappers. The high oxygen barrier property is especially important in applications that can have an impact on shelf life.
Potential solution
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| Image: ExxonMobil |
To move to a mono-material structure or an all-PE alternative, collaboration across the value chain is key. In this case, the ExxonMobil team worked with the following companies: flexible packaging manufacturer Tobe Packaging Industries Pte Ltd, and Aegis Packaging — a Singaporebased company that manufactures high-oxygen barrier coating for flexible plastic packaging.
Tobe created a non-oriented film using ExxonMobil’s performance polyethylene Exceed™ Stiff in the substrate layer. This substrate layer was subsequently laminated with a sealant film. This material was subjected a series of tests for processibility, stiffness, barrier properties, bubble stability as well as melt properties.
Compared with the traditional multi material structure using a non-PE substrate, this mono-material structure demonstrated a significant boost in stiffness in addition to good melt strength, excellent bubble stability and comparable melt pressure.
For frozen food applications, a silicate polymer coating provided by Aegis was applied to help provide an oxygen barrier that can help preserve the quality and flavor of food products. This high oxygen barrier coating was applied using existing coating/laminating equipment, which meant that no special set-up/equipment was required. Finally, the pouches (converted by Tobe Packaging) were ready to be used in frozen food applications.
Results
According to ExxonMobil, tests performed on the material demonstrated:
• Boost in stiffness when Exceed™ Stiff performance polyethylene was used as the substrate film replacing the traditional LLDPE • High oxygen barrier properties that are comparable to multi-material low barrier structures, which can be more difficult to recycle
A key enabler to materializing PE//PE solutions with sustainability benefits is innovative materials and excellent processing. In this instance, it is by combining state-of-art converting technology from Tobe and Aegis together with ExxonMobil Exceed Stiff PE.
