Polycarbonate (PC) is an amorphous engineering thermoplastic produced by polycondensation of bisphenol A with diphenyl carbonate or phosgene. The carbonate backbone provides optical clarity, high dry-ambient impact strength, and heat resistance sufficient for repeated hot-water contact. Those same carbonate linkages are susceptible to hydrolysis, which regenerates bisphenol A and carbon dioxide under melt-processing conditions. Commission Regulation (EU) 2024/3190 deletes bisphenol A from the Union list of authorised monomers in Regulation (EU) No 10/2011 and prohibits its use in food-contact plastics, varnishes, coatings, printing inks, adhesives, ion-exchange resins, and rubber. The former specific migration limit of 0.05 mg/kg under Regulation (EU) 2018/213 no longer applies. Food-contact recycled polycarbonate therefore sits at the intersection of two regulatory regimes: the BPA prohibition and the recycled plastic framework of Regulation (EU) 2022/1616.

Food-Contact Recycled Polycarbonate: Where the EU BPA Ban Leaves Recyclers

The ban leaves recyclers with a stream that cannot be handled as a conventional PET mechanical recycle. Under Regulation (EU) 2022/1616, Annex I identifies established mechanical recycling processes for PET; polycarbonate is absent from that annex. A recycler seeking to place food-contact recycled PC on the EU market must apply for novel technology authorisation supported by an EFSA opinion. The technical dossier must demonstrate decontamination of a monomer that is intrinsic to the polymer backbone rather than an adventitious surface residue. The distinction matters because melt processing of PC does not merely carry over BPA; it creates additional BPA through hydrolysis.

How Does Hydrolytic Chain Scission Regenerate Bisphenol A in Recycled PC?

In the presence of water, the carbonate linkage of PC undergoes hydrolytic scission to form bisphenol A and carbon dioxide. This reaction is accelerated at the 280 °C to 320 °C barrel set points used for compounding and injection moulding. Virgin PC suppliers specify drying to below 0.02 wt% moisture at 120 °C for 4 h in desiccant dryers. Polycarbonate absorbs 0.15 % water after 24 h at 23 °C and approximately 0.35 % at saturation under ISO 62:2008. At relative humidity above 60 %, post-consumer flake stored in open bays can accumulate enough surface moisture that melt-phase hydrolysis is measurable as an upward shift in melt volume-flow rate before visible yellowing appears. The resulting free BPA is only partially removed by degassing.

On a co-rotating twin-screw extruder with L/D 40:1 and a downstream vacuum vent, devolatilisation reduces free BPA but does not eliminate it. The zero-shear viscosity of PC at 300 °C is high enough that bubble nucleation and volatile transport are diffusion-limited. Screw designs using triple-start kneading blocks, pressure-neutral vent zones, and surface-renewing elements improve removal. Equipment suppliers commonly recommend absolute vent pressures below 20 kPa for volatile stripping of high-molecular-weight polycarbonate; however, published data for end-to-end BPA removal rates from real post-consumer bale-derived PC flake is limited. Most studies use virgin pellets spiked with BPA or low-molecular-weight surrogates, which do not reproduce the bulk viscosity and particulate contamination of flake.

Regulatory Text and Analytical Verification for Recycled Polycarbonate

Commission Regulation (EU) 2024/3190 removes the bisphenol A entry from Annex I to Regulation (EU) No 10/2011. The prohibition applies to the use of BPA in the manufacture of food-contact plastics and other food-contact materials. The earlier ban on BPA in polycarbonate infant feeding bottles under Regulation (EU) No 321/2011 removed one historical waste stream; the 2024 measure extends the restriction to all food-contact PC. For recycled material, BPA generated by hydrolysis is assessed as a non-intentionally added substance under Article 19 of Regulation (EU) No 10/2011. Analytical verification of BPA migration uses EN 13130-13:2004, based on high-performance liquid chromatography with fluorescence detection. A validated method may achieve a limit of quantification near 0.01 mg/kg in aqueous food simulants, although the exact limit is method- and matrix-specific. Migration testing under Annex V of Regulation (EU) No 10/2011 for long-term storage at room temperature is commonly carried out at 40 °C for 10 days.

Chemical depolymerisation of PC to bisphenol A does not provide a direct food-contact compliance shortcut. Even if alkaline hydrolysis or alcoholysis recovers BPA at high purity, the recovered monomer cannot be used as an authorised starting substance in food-contact PC under Commission Regulation (EU) 2024/3190. Chemical recycling of post-consumer PC may therefore be redirected to non-food polycarbonate or to other chemical intermediates, while food-contact recyclers must focus on physical decontamination and process validation rather than monomer recovery.

When Post-Consumer PC Is Blended with Virgin Resin for Food-Contact Moulding

Blending recycled PC with virgin PC may reduce the total measured BPA concentration in proportion to the recycled fraction, but dilution is not a stand-alone decontamination technology under Regulation (EU) 2022/1616. The final blend must still meet the BPA prohibition and the NIAS safety requirements of Article 19. On production-scale injection moulding lines with clamp forces above 2,000 kN, pellet-to-pellet MVR variability in unprepared dry blends can exceed 4 cm³/10 min because post-consumer flake carries variable thermal history and moisture. That variability appears as short-shot hesitation, unstable packing pressure, and differential shrinkage in multi-cavity reusable food containers. A 20 wt% recycled content blend often retains tensile stress at yield above 58 MPa under ISO 527-2:2012, while elongation at break may fall by 30–60 % compared with virgin resin. The loss of ductility is not solely a contaminant effect; it is driven by molar mass reduction from repeated melt processing and hydrolytic chain scission on the flake surface.

PC food-contact articles are frequently exposed to hot water and industrial dishwashing. The glass transition temperature of virgin PC is approximately 147 °C under ISO 11357-2:2020. Heat deflection temperature under 1.82 MPa is commonly 125–132 °C under ISO 75-2:2013. Recycled PC with shortened chains may show a 2–8 °C depression in glass transition temperature and a lower Vicat softening point, which can permit distortion during steam-injected cleaning cycles. The practical service boundary is therefore shifted even when short-term tensile strength remains acceptable.

Vacuum Devolatilisation Limits, Melt Filtration, and Molar Mass Preservation

Vacuum devolatilisation of PC melt is constrained by the same chain stiffness that gives PC its high heat resistance. At 300 °C the melt has a high zero-shear viscosity; reducing the vent pressure below 10 kPa improves free BPA removal but can cause melt foaming that destabilises pellet strand formation. Equipment suppliers report throughput limitations when vent pressure drops below 10 kPa absolute because of strand porosity and pellet bulk-density reduction. The operational window is therefore narrow: vent pressure must be low enough to strip BPA but high enough to avoid collapse of the melt pool at the vent. This limitation is not encountered in PET recycling because PET melt viscosity is lower at processing temperature and the contaminant profile is different.

Melt filtration can remove solid particulates from post-consumer PC, but it does not remove dissolved BPA. Screen changers with aperture sizes from 20 µm to 40 µm are used to capture polyolefin cap fragments, label fibres, and adhesive particles. These contaminants affect surface quality and mechanical consistency, but they are easier to manage than monomer-level migration. Recyclers that process food-contact candidates must therefore add offline chemical verification to conventional filtration and extrusion quality controls.

Recyclers that dry PC to below 0.02 wt% moisture may still observe free BPA reformation if the vacuum vent is not maintained below 20 kPa absolute or if the melting-zone screw temperature exceeds 320 °C. The material cannot be certified as food-contact recycled polycarbonate on the basis of MVR alone. Each production campaign must be supported by migration testing under EN 13130-13:2004 and by a process dossier showing that the BPA burden of the incoming waste is controlled. Without that evidence, the lot is suitable only for non-food applications such as automotive and electrical components.