Polycarbonate (PC) is an amorphous thermoplastic produced by the interfacial condensation of bisphenol A with phosgene or by melt transesterification. The carbonate linkage in the backbone is responsible for the combination of high transparency, high impact resistance, and notch sensitivity. Typical unfilled polycarbonate exhibits density 1.20 g/cm³ under ISO 1183-1:2019, tensile stress at yield 60–65 MPa per ASTM D638-14, flexural modulus 2.3–2.4 GPa per ISO 178:2019, and notched Izod impact above 600 J/m per ASTM D256-10(2018). These values are conditional on pre-drying to a moisture content below 0.02% by weight and on moulding within the supplier’s thermal limits.

The SABIC Polycarbonate Short Codes: 118W, 123R, 141R, 143R and PC945 cover a controlled viscosity spectrum for thin-wall injection moulding, general-purpose injection moulding, structural sections, extrusion, and flame-retarded electrical enclosures. The short codes are not merely viscosity variants; they include differences in UV stabilization and combustion performance that affect processing, secondary operations, and regulatory documentation.

How Do the Five SABIC Polycarbonate Short Codes Separate by Melt Rheology and Additive Chemistry?

The primary separation is nominal melt volume-flow rate measured at 300 °C under 1.2 kg load according to ISO 1133-1:2022. The high-flow 118W is positioned for thin-wall parts, 123R is a low-viscosity general-purpose injection grade, 141R occupies the mid-flow range, 143R is intended for higher-melt-strength extrusion and thick-section moulding, and PC945 adds flame-retardant chemistry while retaining an injection-mouldable flow profile. Table 1 summarizes representative process windows reported in supplier technical bulletins; lot-to-lot MVR is controlled within narrower internal limits and should be confirmed against the current datasheet for the specific production campaign.

The flow hierarchy has direct production consequences. A higher MVR reduces injection pressure and permits filling of walls below 1.5 mm, but it also increases molecular orientation and can lower annealed impact retention. Conversely, a lower MVR provides melt strength for sheet and profile extrusion but can produce flow hesitation in thin ribs and bosses. The selection of 118W versus 123R is therefore driven as much by wall thickness and runner balance as by outdoor weatherability. Because polycarbonate MVR is moisture-sensitive, the test specimen must be dried to 0.02% moisture before measurement; otherwise the flow value is inflated by hydrolytic chain scission and the reported number cannot be compared to supplier data. Incoming-quality checks commonly use ISO 1133-1:2022 within 4 h after drying. A deviation of ±2 cm³/10 min from the lot-release value may indicate molecular weight regression, contamination by a higher-flow polymer, or excessive regrind.

Drying, Thermal Stability, and Barrel Residence Constraints

Polycarbonate undergoes hydrolytic chain scission at processing temperatures if water is not removed below 0.02%. A closed-loop desiccant dryer with a dew point of −30 °C or lower, inlet air temperature 120 °C, and residence time 2–4 h is standard for virgin material. When ambient relative humidity exceeds 60%, resin should be dried immediately from original moisture-barrier packaging; hopper-dryer residence alone is not reliable for material exposed more than 30 min. Moulding with moisture above 0.05% produces splay and silver streaks on the part surface and can reduce notched Izod impact by more than 20% because chain scission lowers molecular weight. In production, melt temperature for 123R, 141R, and PC945 is normally held between 280 °C and 305 °C; high-flow 118W can be processed in thin-wall tools at 270–295 °C to reduce degradation at hot-runner gates. Barrel residence time should not exceed 8 min at 300 °C. For machines equipped with 20:1 L/D screws and shot capacities between 40% and 80%, cumulative thermal history remains controlled. Hot-runner manifolds with unbounded internal dead zones have been observed on production lines to generate black specks and yellow streaks when colour-stable 123R is run at 305 °C with a residence time over 12 min; replacement of the manifold or reduction of the barrel setpoint corrected the degradation.

Mould temperature is equally critical. At mould temperatures below 60 °C, polycarbonate freezes in residual stress, and the part becomes more susceptible to environmental stress cracking in contact with aromatic hydrocarbons, ketones, chlorinated solvents, and amines. For 118W, 80–90 °C mould temperature allows thin walls to pack and reduces birefringence in transparent optical parts. For 141R and 143R, 70–95 °C is typical for thick sections. Excessive drying is also a production variable. Prolonged exposure above 130 °C can cause pellets to stick in the hopper and can increase yellowing in clear grades. A desiccant bed that is not regenerated to −40 °C dew point will gradually raise equilibrium moisture in the resin and produce intermittent splay. Moisture analyzers using weight-loss methods may under-report water in PC because the resin is sensitive to thermal history; Karl Fischer titration on dry pellets is preferred.

On a 1200-kN clamp force injection-moulding machine with a 35 mm diameter screw and 20:1 L/D, 118W is typically injected at hydraulic pressure 80–110 MPa and held at 60–80% of that pressure during packing. Flow length-to-wall-thickness ratio at these settings is maintained between 80:1 and 120:1. 123R is used on the same equipment for bezels and lenses where wall sections are 2.0–3.0 mm; its lower MVR relative to 118W permits lower injection speeds without gate blush. Mould shrinkage after 48 h at 23 °C is generally 0.5–0.7% in the flow direction and 0.6–0.8% transverse under ISO 294-4:2018, depending on wall thickness and mould temperature. When 118W is used in LED lenses and clear covers, the higher flow creates anisotropic shrinkage in thin walls; pack pressure should be high enough to hold the gate seal, but excessive hold time beyond gate freeze has no additional effect.

123R and 141R both accept colour concentrates and can be used in transparent or opaque formulations. In a production-scale central drying system, batch-to-batch variance in pellet shape and lubricant levels changes the drag coefficient in the screw feed zone; settings for back pressure below 0.5 MPa are common for unfilled PC, and higher back pressure can raise melt temperature without raising barrel setpoint. Short shot studies on a 141R part with 2.5 mm nominal wall show the gate freeze time is reached at approximately 4–6 s under a mould temperature of 80 °C; packing prior to gate freeze is needed to reduce sink marks over ribs. Ejection is normally delayed until the part surface is at or below 125 °C, since PC retains heat in thick bosses and can deform if ejected above the deflection temperature under load.

When 141R and 143R Are Selected for Structural Profiles and Solid Sheet

Although both 141R and 143R can be injection moulded, 143R is the standard extrusion grade where melt strength and low melt flow are required to prevent sag in solid sheet and profile dies. Extrusion of 143R on a single-screw machine with 25:1 L/D and a barrier screw with compression ratio 2.0:1 to 2.5:1 uses barrel setpoints from 250 °C to 280 °C, die temperature 260–285 °C, and polished die lips to minimize surface blemishes. 141R is selected for structural brackets and housings with wall thickness 3.0–5.0 mm; its MVR window reduces fill pressure while maintaining notched Izod impact above 600 J/m when moulded at 280–300 °C and 70–90 °C mould temperature. For both grades, annealing at 110 °C for 30 min per 10 mm of wall thickness is applied where high mechanical loads and solvent exposure are expected. Draw ratio in sheet extrusion is maintained below 10:1 to control orientation and reduce thickness variation. In solid sheet extrusion, breaker plates and screen packs with 40/60/80 mesh layers are used to raise head pressure and remove contaminants. A melt pump upstream of the die smooths output, and a stainless steel die with chrome-plated lips is preferred over untreated steel because PC can pick up iron and generate black specks.

PC945 enters the portfolio as the flame-retardant polycarbonate short code specified for electrical enclosures, battery housings, and control boxes requiring UL 94 V-0 at 1.5 mm. The fire-retardant package modifies thermal stability; barrel setpoints are held at 260–285 °C rather than the upper range used for 123R, because prolonged exposure above 300 °C can generate acidic decomposition products and black specks. Injection shops running PC945 on a 1000-kN press with a hot-runner system have reported more consistent colour and mechanical retention when the virgin resin is pre-dried at 120 °C for 4 h to below 0.02% moisture and the hot-runner manifold is maintained at 285 °C. The grade is commonly assigned to parts that must satisfy IEC 60695-11-10:2013 flame index or UL 94; published data for this specific configuration is limited, so the current supplier datasheet is the controlling document. When PC945 is moulded in colours other than black or natural, the flame-retardant package may require thicker walls or specific colorants to maintain UL 94 V-0; each colour formulation must be recertified. After moulding, PC945 parts can show plate-out on mould surfaces; frequent cleaning of vent pins and gas-vent channels is needed. Vent depth below 0.03 mm is typical to prevent flash while allowing volatiles to escape; blocked vents increase burn marks and reduce flame performance because degradation products remain in the part.

Certification Routes Depend on Final-Part Geometry and Additive Package

Food-contact versions of these short codes may be certified against FDA 21 CFR 177.1580 for polycarbonate resins, subject to end-use limitations for food types and temperatures. The EU food-contact route is often supported under EU 10/2011 where overall migration below 10 mg/dm² must be verified on the final article; however, not every short code in each region carries the same approval. Electrical grades such as PC945 are evaluated under UL 94 and IEC 60695-11-10:2013, while the base resins can be assessed under REACH Regulation (EC) No 1907/2006 and RoHS Directive 2011/65/EU. Table 2 summarizes the constraints most frequently requested in production.

Because polycarbonate is notch-sensitive under severe impact and susceptible to stress cracking in the presence of aromatic hydrocarbons, ketones, chlorinated solvents, and amine-cured coatings, selected short codes should not be auto-painted or cleaned with aggressive solvents without compatibility testing. Avoid processing with amine-based additives or acetal resins in the same hot-runner system. The user is responsible for verifying that the specific short code ordered from SABIC meets the lot-specific physical property, colour, and regulatory requirements before production release.