Polycarbonate (PC) and the procurement shorthand “Poly Carb” refer to the same amorphous thermoplastic family derived from bisphenol A and phosgene or diphenyl carbonate. The formal registry identifier is CAS 25037-45-0, with density 1.20 g/cm³ under ISO 1183-1:2019. Buyers entering “Poly Carb” in a search bar are normally specifying unfilled transparent, opaque, or flame-retardant grades with tensile yield stress 60–65 MPa under ASTM D638-14 and notched Izod impact 600–850 J/m under ASTM D256-10. The syndicated query phrase “Poly Carb and Polycarbonate: The Shorthand Names Buyers Actually Type” captures this dual input pattern; it does not identify a separate resin chemistry. Because “Poly Carb” does not encode filler loading, UV stabilization, melt-flow class, or food-contact status, procurement specifications must be resolved to a supplier datasheet with a defined melt volume-flow rate measured at 300 °C and 1.2 kg load per ISO 1133-1:2022.

Why Does the Search Term “Poly Carb” Collapse into Grade Families?

Commercial polycarbonate grades are differentiated by melt volume-flow rate rather than by the abbreviation recognized in purchasing databases. A grade referred to only as “Poly Carb” may fall into MVR bands that determine downstream equipment selection. Table 1 summarizes four process-relevant bands encountered in supplier datasheets; values are normalized to ISO 1133-1:2022 at 300 °C with a 1.2 kg piston load.

An MVR of 10–20 cm³/10 min is the default for general-purpose injection molding, while extrusion grades are deliberately held at 6–10 cm³/10 min to maintain melt strength. A buyer typing “Poly Carb” without a suffix therefore requires a technical review of the part drawing before resin substitution is accepted.

The Drying Window Is a Hard Constraint, Not a Recommendation

Pre-drying is mandatory because the carbonate linkage in polycarbonate hydrolyzes at processing temperature when residual moisture exceeds 0.02%. Desiccant-bed dryers with a dew point of -40 °C and a drying temperature of 120 °C for 3–4 h are the baseline specified in supplier technical bulletins. In production lines where ambient relative humidity exceeds 60%, drying residence should be extended to the upper limit, and hopper capacity must maintain at least 4 h of material inventory at full shot rate. Failure to maintain moisture control produces splay, silver streaks, and notched Izod values that fall below the 600 J/m threshold associated with unfilled PC under ASTM D256-10.

The melt processing window for unfilled polycarbonate is generally 280–320 °C at the nozzle, with mold temperatures maintained at 80–100 °C. Barrel temperature profiles should ramp from 260 °C in the feed zone to 280–300 °C in the compression zone and 300–320 °C at the metering zone/nozzle. A screw with L/D ratio of 20:1 and compression ratio 2.0:1–3.0:1 is common for injection molding; compounding operations use vented twin-screw extruders at L/D 32:1–36:1 to permit devolatilization. Local residence time above 10 min at temperatures over 320 °C causes yellowness index increase under ASTM E313-20 and molecular weight loss; shutdown purges should use an acrylic or low-MFR purge compound with matching viscosity.

Transparent polycarbonate grades are specified by total luminous transmittance of 89–90% at 3.0 mm thickness under ASTM D1003-21 and haze below 1% for polished molded plaques. UV-stabilized grades intended for outdoor glazing retain notched Izod performance and color stability after accelerated weathering under ISO 4892-2:2013, but published data for this specific configuration of tropical outdoor exposure beyond the accelerated test is limited. Polycarbonate should not be processed with free amine-based flame-retardant additives or strongly alkaline residues because carbonate linkage degradation is accelerated at processing temperatures.

When a Drawing Requests “Poly Carb” Without a Melt-Flow-Rate Designation

Drawings that list only “Poly Carb” without MVR, filler, or flame rating force a review of load, temperature, and chemical exposure. For load-bearing covers, polycarbonate’s flexural modulus is reported at 2.3–2.4 GPa under ASTM D790-17, and heat deflection temperature under 1.82 MPa load is 126–138 °C per ASTM D648-18, depending on grade. These values establish the upper service temperature for unfilled PC but do not account for chemical contact. Electrical arc resistance and comparative tracking index for flame-retardant grades are specified by IEC 60112.

Secondary operations such as threading, solvent bonding, and adhesive joining introduce stress-cracking risks. Unfilled polycarbonate in contact with acetone, toluene, or aromatic hydrocarbons may craze at molded-in stress zones. Stress-relief annealing is conducted at 121 °C for 1 h for parts above 6 mm wall thickness. Milling and drilling require low feed pressure and sharp carbide tooling to prevent microcrack initiation; post-machining annealing may be omitted only if molded stress is below the limit identified by polarized light inspection.

Flame-retardant and outdoor grades should not be substituted into parts that contact chlorinated solvents or strong alkali cleaning agents at elevated temperature. In applications requiring repeated steam sterilization, unfilled medical polycarbonate may retain tensile yield stress near 60 MPa after limited autoclave cycles, but the peroxide or amine residuals in some cleaning fluids can induce surface whitening and loss of notched Izod by accelerating hydrolysis.

Compliance Matrix for Food-Contact and Flame-Retardant Grades

Polycarbonate grades used for food-contact articles are evaluated under FDA 21 CFR 177.1580 and EU Regulation 10/2011; migration limits for bisphenol A are enforced where the resin is used in infant feeding bottles under regional directives. The abbreviation “Poly Carb” does not automatically confer food-contact status; only grades listed with the relevant regulatory citation on the supplier certificate of compliance meet these requirements. Flame-retardant grades are tested to UL 94; general-purpose unfilled PC typically attains V-2 at 3.0 mm, while halogen-free flame-retardant grades can achieve V-0 at 1.5 mm with reduced afterglow time.