Flexible film packaging structures primarily based on polyethylene (PE), polypropylene (PP), or polyethylene terephthalate (PET) are increasingly advocated as effective tools for advancing mechanical recycling efforts, despite being commonly disposed of alongside mixed plastic waste for now. Recent material developments and the proliferation of conversion machines capable of stretching PE either uniaxially or biaxially suggest a growing adoption of these mono-material structures as easily recyclable flexible packaging solutions, provided appropriate collection systems are established.
Two crucial processes for replacing multi-material packaging formats with mono-material alternatives are biaxially-oriented PE extrusion/stretching of cast film and machine direction orientation (MDO) stretching of blown film. These methods involve stretching specialized grades of high-density PE (HDPE) in conjunction with linear-low-density PE (LLDPE) to confer adequate stiffness to the structure, allowing HDPE to substitute the layers of BOPP, oriented polyamide (BOPA), or oriented PET (BOPET) typically utilized. Mono-material structures must also be engineered to accommodate printing and incorporate sealant layers.
Reifenhäuser, a supplier of MDO-PE blown film lines, boasts nearly 30 of its Ultra Stretch MDO units deployed worldwide. According to Sascha Skora, senior sales manager for blown film at Reifenhäuser, MDO offers advantages over BOPE in terms of line output, cost-effectiveness, retrofitting capabilities, and flexibility. Meanwhile, Nova Chemicals anticipates that BOPE-HD will offer improved puncture resistance, particularly in applications subject to higher levels of abuse or drop impact, while also supporting high-quality printing.
Brückner Maschinenbau, a BOPE line supplier, actively participates in the mono-material market with hybrid lines capable of converting both PE and PP structures. Approximately 20 such lines are either operational or scheduled for installation in the coming year. These lines offer flexibility in switching between PE and PP production, with considerations for resin performance attributes necessitating die changes when transitioning between the two resins.
Stretchable HDPE is a critical component of PE mono-material structures, with Nova Chemicals leading material development efforts for both MDO and BOPE processes. Nova's Surpass TX150 grade, designed for use in existing commercial tenter frame lines producing BOPP films, exemplifies this advancement. According to Nova, the largest opportunity for BOPE-HD film lies in replacing non-recyclable mixed-material packaging, such as standup pouches made from BOPET, with easily recyclable alternatives.
In terms of applications, Nova Chemicals highlights three main types of high-density films—high clarity, matte, and sealable BOPE films—used in various packaging formats, including standup pouches, vertical bags for frozen food, pet food packages, and flow wrap applications for candies or snack bars. These advancements represent a significant step toward achieving recyclability in packaging solutions that were previously challenging to transition.
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