Low-density polyethylene (LDPE) is produced by high-pressure free-radical polymerisation and is characterised by a density range of 0.910–0.940 g/cm³ measured to ISO 1183-1:2019, with film-extrusion grades commonly specified at a melt flow index of 0.5–2.0 g/10 min under 190 °C/2.16 kg per ISO 1133-1:2022. In flexible packaging, LDPE supplies melt strength, heat-seal response, and downgauging capacity. When post-consumer recyclate is introduced, the specification of PCR LDPE for packaging must resolve certification, traceability and the price gap relative to virgin resin, because batch heterogeneity in density, melt flow index, gel load, and odour directly controls film-line stability.

What certification evidence must a converter obtain for PCR LDPE in food packaging?

For non-food packaging, claims of recycled content are verified against EN 15343:2007 and ISO 14021:2021; certification schemes such as EuCertPlast and RecyClass provide audit frameworks aligned with those standards. A converter should require a certificate of conformity per delivery lot, a recycled-content declaration, and batch results covering melt flow index, density, ash content, moisture, and gel count. In food-contact film, Regulation (EU) 2022/1616 replaces Regulation (EC) No 282/2008 and requires that recycled plastic be obtained through a suitable recycling technology and, where relevant, an authorised process. In the United States, FDA 21 CFR 177.1520 governs olefin polymers, and PCR LDPE use is reviewed through a food-contact notification or a no-objection letter for a specific recycling process.

Traceability for PCR LDPE packaging is often audited under ISO 22095:2020 and is implemented through a mass balance ledger that records input batch number, recycled weight, virgin weight, process scrap, and output reel weight. Under the controlled blending model, a converter may feed natural rLDPE and virgin LDPE from separate gravimetric hoppers into the extruder throat; the recycled-content claim is then assigned at the finished-product level rather than at the pellet level. For segregated supply, separate silos, vacuum loaders, and sampling equipment are required to prevent cross-contamination. EN 15343:2007 reinforces this by requiring the recycler to demonstrate that the declared recycled content derives from traceable waste plastic and that non-conforming material is quarantined. A single missing weighbridge ticket or a batch where the balance cannot be reconciled invalidates the recycled-content claim under most certification rules. Converter audits commonly identify undocumented process scrap as the largest source of claim error.

Price Gap Drivers in Natural PCR LDPE Film Resin

The commercial gap between natural PCR LDPE film pellets and virgin LDPE cannot be read from a single index price because it depends on bale classification, colour sorting, melt filtration, certification, and regional packaging levies. The EU plastic packaging levy under Council Decision (EU, Euratom) 2020/2053 imposes €800/tonne on non-recycled plastic packaging waste, and this factor changes the effective price ceiling that a converter can pay for certified PCR LDPE. For a laminate with 30% recycled content, the avoided levy benefit is based on the certified recycled share of the finished article rather than on the virgin fraction. If sorting and washing losses reach 30%, the usable PCR LDPE yield from a bale is only 0.70 kg/kg, and the feedstock cost per usable kilogram rises accordingly. Melt filtration with a 125 µm screen removes gels but also removes some polymer matrix, creating a compounding yield loss of 2–5%. When natural rLDPE pellet supply is tight, the price gap can invert because converters needing packaging with a defined recycled fraction have limited substitution options.

For blown film production on a three-layer coextrusion line with die diameter 160 mm, die gap 1.8 mm, blow-up ratio 2.5:1, and frost line height 400–450 mm, a core layer containing PCR LDPE requires a screw configuration with low shear mixing and high melt stability. Single-screw extruders of 45 mm diameter and L/D 30:1 are used for PCR LDPE, but the screw should have a barrier section and a venting zone at -0.08 MPa to remove water and low-molecular-weight compounds. A continuous screen changer with two packs of 100 µm and 150 µm mesh lowers gel-induced bubble-break frequency. Inline melt pumps reduce pressure variation at the die below ±0.2 MPa, which is important when recycled LDPE melt flow index varies by 0.3–0.5 g/10 min between lots. Barrel temperatures are commonly set at 190–210 °C for the feed and compression zones and 200–215 °C at the metering zone; higher temperatures improve melt homogeneity but increase oxidation and odour. Film properties are tested to ASTM D882 for tensile, ISO 7765-1:2004 for dart impact, and ASTM D1922 for Elmendorf tear. When PCR content exceeds 50%, the variation in gel count and melt flow index often requires reducing line speed by 10–15% compared with virgin LDPE under the same die and cooling geometry.

Batch-to-batch variation in natural PCR LDPE is typically higher than virgin LDPE because the input consists of mixed flexible film types, including LLDPE and EVA. Density separation in a sink-float tank with a water bath at 0.995–1.000 g/cm³ removes polypropylene and some polyethylene copolymers only if the density difference exceeds the process resolution; flexible multilayer films with EVOH or PA tie layers remain a source of contamination. A Fourier transform infrared system on the sorting line can classify approximately 90–95% of LDPE film by polymer type, but black articles and multilayer structures may be missed. The resulting melt flow index of PCR LDPE can shift from 0.5 g/10 min to 1.5 g/10 min within a single production lot if chain scission dominates during repeated extrusion.

When Gel, Odor, and Clarity Limits Restrict PCR LDPE Addition Levels

In high-clarity collation shrink film and food overwrap, PCR LDPE addition levels are dictated by visible gel count, not tensile strength alone. A single gel larger than 200–300 µm in a 30 µm film can initiate bubble instability or form a point source for dart impact failure. Converters therefore specify gel counts below 20–50 gels/100 cm² for surface layers, measured with a film scanner or a manual light box; natural PCR LDPE that fails this threshold must be diverted to black or opaque construction film where the specification allows higher gel loads. Odour thresholds are equally restrictive: a recycled LDPE film intended for direct food packaging is often screened using a sensory panel and may be compared to VDA 270 for automotive interior odour, but no single ISO method covers all packaging odour limits. Residual fatty acids, soap, or oxygenated compounds from post-consumer film can form volatile aldehydes during extrusion; vacuum degassing removes some fraction but does not remove semivolatile contaminants bound in the polymer matrix. If the target film requires a haze value below 10% per ISO 14782:2021, darker PCR LDPE cannot be used in skin layers, and natural PCR LDPE may require an additional filter run at 80 µm to reduce micro-gel haze. Published data for specific incoming bale compositions is limited; therefore, each converter must fix the maximum PCR content after pilot trials on the target line using a stabilised lot and a qualified film grade.

Under Regulation (EU) 2022/1616, mechanical recycling of post-consumer LDPE is not considered a suitable technology for direct food contact unless the input is from a closed and controlled product loop or the process receives specific authorisation based on challenge-test data and EFSA evaluation. In multilayer packaging, PCR LDPE is therefore placed behind a virgin LDPE functional barrier; migration modelling under Regulation (EU) 10/2011 must show that potential contaminants do not exceed their specific migration limit in the food simulant. The barrier layer thickness is commonly set at 20–35 µm, but the safe thickness depends on diffusion coefficients, contact time, and temperature; a high-temperature pasteurisation step at 85 °C for 2 min changes the migration calculation because diffusion coefficients rise sharply with temperature. In the United States, FDA 21 CFR 177.1520 clears olefin polymers for food contact, but PCR LDPE requires a separate FDA no-objection letter for the recycling process; the letter typically specifies the maximum recycled content and end-use conditions. Converters must maintain supplier documentation for each batch, retain production records for at least 3 years depending on the certification scheme, and subject the finished package to periodic migration testing or modelling verification.