Polyethylene terephthalate (PET) used in rigid packaging is specified by intrinsic viscosity (IV), crystallinity, acetaldehyde (AA) concentration, colour coordinates, and melt filterability. Bottle-grade virgin PET normally shows an IV of 0.78–0.84 dL/g when measured according to ASTM D4603-18 or ISO 1628-1:2021. In client contracts, the recycled PET share is not a single mass percentage; it is an envelope of constraints that determines whether post-consumer recycled (PCR) flake or pellet can be processed without violating the preform specification. Mechanical reclamation of baled bottles combines sorting, size reduction, density separation, hot caustic washing, flake sorting, melt filtration, and optional solid-state polycondensation (SSP). Each unit operation changes the molecular weight distribution and the residual contaminant load used to price the PCR share.

For bottle-to-bottle recycling, the accepted feedstock is usually clear or light-blue baled bottles with caps and labels removed as far as possible. A flake-to-preform yield loss of 2–5% is common when dust, fines, and non-PET flakes are removed; this loss is allocated in the contract either to the flake supplier or to the converter. The cost of the PCR share therefore includes not only the price of the recycled resin but also the yield adjustment, the analytical testing burden, and the technical limits of the injection or extrusion line.

What Makes PCR Content a Specification Variable Rather Than a Drop-in Diluent?

The PCR pellet entering a preform injection machine is not chemically equivalent to virgin PET. It has experienced at least one additional melt history and, without SSP, a measurable loss of IV due to hydrolytic and thermal oxidative chain scission. The extent of this loss depends on residual moisture before extrusion and the residence time distribution in the melt phase. Washed flake conditioned to 200–400 ppm moisture can lose 0.02–0.05 dL/g IV in a single melt-compounding pass because water attacks ester linkages at melt temperatures above 270°C. Vacuum devolatilization on a co-rotating twin-screw extruder with L/D 40:1 and 10–30 mbar absolute pressure removes water and free AA but cannot rebuild IV once chain scission has occurred.

Acetaldehyde is generated from vinyl ester chain ends and residual AA precursors. In water-bottle preforms, a headspace concentration above 1 ppm measured by ASTM F2013-10 is generally considered organoleptically unacceptable. Washed clear flake can carry 5–10 ppm AA before extrusion, while a food-grade SSP pellet is typically specified below 1 ppm. Colour is equally binding. CIELAB b* values determined by ASTM D6290-19 on clear washed flake frequently fall between 5 and 12, whereas bottle-grade PCR pellets may require b* below 3 to avoid visible yellowing in a clear preform. These thresholds make the PCR share in a client contract a specification variable, not a simple dilution ratio.

Solid-state polycondensation is the standard industrial route for restoring IV and reducing AA in bottle-grade recycled PET. Continuous SSP reactors hold crystallised pellets under an inert nitrogen flow at 190–215°C for 10–18 h, depending on the starting IV and target AA. The rate is controlled by diffusion of ethylene glycol and acetaldehyde from the pellet core, not by catalyst concentration alone. Industrial PCR SSP feed is crystallised to at least 35% to prevent pellet agglomeration. With this route, a flake IV of 0.70–0.76 dL/g can be raised to 0.78–0.82 dL/g, but SSP cannot remove PVC, polyolefin, or thermoset residues.

Melt filtration before SSP determines downstream pressure stability in the converter’s injection screw. A 40 µm screen pack is typical for bottle-grade PCR, but residual PVC and crosslinked polymer concentrations as low as 5–20 ppm can shorten screen pack service life below one shift. The converter’s limiting variable is often hot-runner pressure drop, not clamp force. If the PCR share is raised without tightening the filtration specification, preform weight variation and black specks appear long before the mould itself loses function.

Pre-drying is an operational boundary that influences the price of the PCR share. Wet rPET pellets exceeding 50 ppm moisture before injection moulding undergo hydrolytic IV loss at the screw. Drying systems for rPET typically specify hopper dryers with a dew point of −40°C and a residence time of 4–6 h at 160–170°C. The cost of drying is sometimes allocated to the PCR share in client contracts because virgin PET may be supplied with lower residual moisture. Failure to maintain the dryer dew point creates batch-to-batch variance that downstream moulding cannot correct.

When the PCR Premium Is Quoted as a Differential to Virgin Resin Index

Client contracts usually price the PCR share as a differential to a published virgin PET resin index. The general formula separates the certified PCR mass fraction from the technically usable fraction:

P = P_v + X(P_r − P_v + C_SSP + Q_IV + Q_colour + L)

where X is the recycled mass fraction, P_v is the virgin PET reference, P_r is the washed flake or PCR pellet reference, C_SSP is the conversion cost for solid-stating and pelletizing, Q_IV and Q_colour are quality adjustments, and L is logistics or handling cost. In this structure, the PCR premium is not a fixed adder; it becomes negative when flake is scarce or virgin resin is long, and rises when food-grade SSP pellet supply is tight.

European clear PCR flake and food-grade pellet indices are maintained by subscription price reporting agencies such as ICIS and S&P Global Commodity Insights; public aggregated data for exact monthly spreads are limited. The contract price often references a monthly average index and adds a fixed converter margin per tonne for SSP and pelletizing. If the delivered IV falls below the contract minimum, the batch may be repriced as non-food flake or rejected entirely, which means the lower-cost PCR share can become the most expensive line item in the preform cost model.

Yield accounting at the preform line is the least visible but often largest adjustment. A PCR share of 30% by weight in the bottle does not mean 30% of the preform weight is recycled PET if the screw feed is topped with off-spec sprues, start-up scrap, and purgings. In controlled blending, the PCR ratio is maintained by gravimetric feeders with a short-term accuracy of ±0.25 wt%; deviations beyond this range cause the final package to fail the contract specification. The cost of lost virgin PET during PCR transitions is assigned to the recycled share in some contracts, making the effective PCR price higher than the flake index suggests.

Chain-of-Custody Verification and EU 2022/1616 Impact on PCR Share

PCR content in PET packaging is verified by chain-of-custody rules, not by a single laboratory measurement of the finished bottle. ISO 22095:2020 defines segregated, controlled blending, mass balance, and book-and-claim models. In bottle contracts, segregated and controlled blending are preferred because mass balance can allocate the certified PCR share to a product that contains little or no physically recycled polymer. The pricing difference between a mass-balance certificate and a physically segregated PCR pellet is measurable: segregated food-grade rPET includes the cost of dedicated storage, separate feeding, and batch changeover, while mass balance can lower logistics cost but may not satisfy all brand owners.

The European food-contact framework is Commission Regulation (EU) 2022/1616, which requires a recycling process to demonstrate decontamination suitability through a challenge test and approval or opinion. Directive (EU) 2019/904 Article 6(5) sets PET beverage bottle recycled content targets of 25% by 2025 and 30% by 2030, measured as post-consumer plastic on average for bottles placed on the market in each Member State. A client contract that references only a percentage without a defined chain-of-custody method and food-contact approval leaves the buyer exposed to claims that cannot be verified at the production line.

If rPET Flake Carries Residual PVC Above 20 ppm

Residual PVC is among the most severe cost drivers in PCR PET because PVC degrades in the PET processing range, releasing hydrochloric acid that catalyses chain scission and accelerates yellowing. Optical flake sorting and density separation can reduce PVC to below 20 ppm in bottle-grade flake, but occasional label sleeves and barrier films still pass through. At melt temperatures of 270–290°C, PVC degrades into conjugated polyenes and hydrogen chloride; even low parts-per-million excursions can shift preform b* and produce surface defects. A PCR share target may be met only if the feedstock specification includes a PVC ceiling, because downstream melt filtration cannot remove chloride once it enters solution.

Polyolefin residues from caps and labels create a separate rheological incompatibility. Polypropylene and polyethylene remain as dispersed domains in the PET matrix, generating haze, interfacial weakness, and variability in melt viscosity. Clear PCR PET feedstock is often controlled to a polyolefin concentration below 50 ppm by density separation and flake sorting. If the contract omits these limits, a lower price per tonne of PCR flake can be offset by injection scrap rates and screen pack replacement intervals. Published line-specific data for some configurations is limited, but the failure modes are consistent: pressure rise across 40 µm screens, vacuum line fouling, and preform weight variability exceeding ±0.5 g when melt viscosity oscillates.

Batch-to-batch verification of PCR PET pellets uses IV and melt viscosity in parallel. Intrinsic viscosity by ASTM D4603-18 is slow, so many converters use melt viscosity by ISO 11443:2014 as a release test because it captures the effect of residual polyolefin and gel particles on flow. A PCR pellet with an IV of 0.80 dL/g can still exhibit shear viscosity spikes if gel contamination exceeds 20 mm²/kg in a pressure filter test. These measurement conditions are part of the contract’s technical annex; a low price per tonne is irrelevant if the pellet cannot pass the release gate.

The processing window for PCR PET preforms narrows as the recycled share exceeds 25%. Barrel temperatures are commonly raised by 5–10°C to compensate for lower melt strength, but this increases AA re-formation. Hot runner balance becomes the controlling variable when recycled flake viscosity fluctuates; 48-cavity preform tools require uniform melt delivery within a narrow pressure band. Melt viscosity measured by capillary rheometry per ISO 11443:2014 at 280°C and 100 s⁻¹ can reveal batch-to-batch variation before injection moulding begins. The contract’s PCR share price must therefore include the converter’s cost of quality control, start-up scrap during transitions, and any derating of injection moulding output caused by the recycled fraction.