1. WHY MIXED STRUCTURES FAIL
Mechanical recycling melts a structure back into resin, and a melt tolerates only one dominant polymer. PET fragments in a PE stream form gels and weak points that rule the recyclate out of quality applications. That is why design-for-recycling (DfR) starts with one core rule: build the pack from one polymer family - for flexibles, normally PE or PP - and keep everything else inside tight limits. Aluminium foil is the clearest fail; a foil barrier makes a flexible pack non-recyclable in practice, which is why metallized PP has taken over barrier jobs where protection and recyclability have to coexist.2. THE THRESHOLDS THAT MATTER
Europe's reference frameworks - the CEFLEX design guidelines and RecyClass - converge on similar numbers. Mono-material polyolefin structures are expected to run above 90% single-polymer by weight, with barrier layers, inks, adhesives and coatings kept to roughly 5% each. Density decides how the pack sorts: PE and PP sit below 1 g/cm3 and float in separation tanks, while heavier polymers sink. Size decides too - very small formats slip through screens and sorting equipment, so they never reach the recycling stream.3. EVERY LAYER COUNTS
Barrier. EVOH, the common oxygen barrier, is generally tolerated up to around 5% of the structure. Thin AlOx or SiOx coatings follow the same limits, and a metallized layer is treated like a coating rather than like foil. Adhesive. Even a mono-material pack is usually a lamination of two PE films, and the adhesive between them counts against the structure - guidance keeps it typically under 5% by weight. Solventless lamination is the standard route here: XIAOPAI supplies the WRJ Fi9 and WRJ i9-1300A solventless laminating machines, which meter adhesive by weight and hold tension in a closed loop across the web, so a bond line designed inside the threshold stays inside it in production. Ink. Coverage and pigment chemistry decide sortability. Carbon-black-heavy designs are a known fail with near-infrared scanners - the sorter reads nothing - while lighter coverage and NIR-readable blacks keep the pack detectable. Fitments. Zippers, spouts and valves should match the pack polymer: a PE zipper on a PE pouch, a PE-compatible valve on a PE coffee pack. How closures and fitments are designed for recycling is set out in this piece from the Flexible Packaging Association: Design of Recyclable Flexible Packaging Closures and Fitments.4. THE PPWR DEADLINE
The rules are becoming law. Regulation (EU) 2025/40 - the Packaging and Packaging Waste Regulation, known as PPWR - applies from 12 August 2026. From 1 January 2030, packaging placed on the EU market must be recyclable at grade C or above; a structure below 70% recyclability is treated as technically non-recyclable and cannot be placed on the market. From 1 January 2038, the bar rises to grades A and B. Eco-modulated producer responsibility links the same design grade to producer obligations in every member state. The collection and sorting side of film recycling is tracked here: Film Recycling Hits a Pivotal Moment.
