Mono-material: A Practical Plan to Replace Multilayer Laminate Films β
Core trend: The EU PPWR requires packaging to meet design-for-recycling by 2030. Traditional PET/AL/PE or BOPA/PE laminate films cannot be recycled because of their mixed materials and are being phased out rapidly. Mono-material has become a matter of survival for flexible packaging.
1. Why Mono-Material Is the Endgame for Flexible Packaging β
In a conventional mechanical recycling and pelletizing plant:
- If PET (melting point approx. 250Β°C) and PE (melting point approx. 120Β°C) are mixed in the same plastic, the PE degrades and chars during high-temperature melting, ruining the entire batch of recyclate.
- A mono-material structure (all-PE or all-PP) needs no separation step when shredded for recycling, and can be pelletized directly as a single, homogeneous resin β a true 100% closed loop.
2. Comparing the Mainstream Substitution Routes β
1. All-PE Structures (Mono-PE) β the Most Widely Adopted β
- Classic structures: MDO-PE (machine-direction-oriented PE film) + PE sealant film, or BOPE + barrier layer + PE
- Advantages: soft, puncture-resistant, excellent low-temperature heat-sealing.
- Challenges overcome:
- Stiffness and heat resistance: high-crystallinity MDO-PE increases rigidity and solves stretching/deformation during printing.
- Barrier solution: nano alumina (AlOx) / silica (SiOx) vapor deposition, or ultra-thin EVOH (β€5% by weight, which does not affect classification of the structure as recyclable PE).
2. All-PP Structures (Mono-PP) β High-Temperature Retort and Rigid-Crisp Scenarios β
- Classic structure: BOPP + solvent-free adhesive + CPP
- Advantages: high transparency and good heat resistance (withstands 121Β°C high-temperature, high-pressure retort sterilization), suitable for zipper stand-up pouches, coffee bean bags and pet food bags.
3. Tooling and Equipment Tuning Essentials β
- Precise heat-seal knife temperature control: Because the melting-point gap between the outer and inner layers shrinks (over 100Β°C for traditional PET/PE, but only 15Β°Cβ30Β°C for all-PE structures), servo-controlled high-precision heat-seal knives are a must to avoid burning through the outer layer.
- Closed-loop tension control: PE film has a low elastic modulus, so tension during printing and lamination must be reduced by 30%β40% to prevent misregistration.