Polycarbonate (PC) is a tough, amorphous thermoplastic supplied as Lexan, Makrolon, Tuffak, and Hyzod sheet and rod stock, with a glass transition temperature near 147°C, a notched Izod impact strength of 600–850 J/m, and a flexural modulus of roughly 2,300–2,400 MPa, per a 2026-07 CNC machining guide [S3] and a 2026-05 plastics selection chart [S4]. A general-purpose unfilled grade already carries UL 94 V-2 flammability without additives, while glass-filled, UV-stabilized, FDA-compliant, abrasion-resistant, flame-retardant (UL 94 V-0), and bullet-resistant laminate grades cover the rest of the spec map [S2].
Selection for general fabrication comes down to three decisions: grade family, machining protocol, and standards match. A fabricator who treats PC like aluminium or acrylic will crack parts, melt edges, or build in stress that shows up weeks later in service. PC is gummy under heat, notch-sensitive, and hygroscopic, and each of those facts has a direct consequence on feeds, tooling, drying, and annealing [S2][S3]. For a broader perspective on how PC compares to neighbouring engineering plastics used in industrial enclosures, see the polycarbonate material profile.
Core property ranges you can quote on a drawing
PC density sits at 1.18–1.22 g/cm³, water absorption runs 0.15–0.35%, and thermal conductivity is 0.19–0.22 W/m·K; light transmittance for clear sheet is roughly 90% [S3]. A separate Chinese-language reference pegs density at 1,200 kg/m³, linear expansion at 3.8×10⁻⁵ cm/°C, and a notched Izod of 600–900 J/m for high-molecular-weight grades, with a heat-deflection temperature of about 130°C for unfilled resin and roughly 140°C after glass-fibre reinforcement [S1]. The two sources agree within machining tolerance, and the slight gap on Izod (850 vs 900 J/m) is the kind of spread a buyer should expect between grade families and test methods [S1][S3].
Mechanical strength is the headline: tensile strength 55–75 MPa, compressive strength 80–90 MPa, and continuous service temperature around 240°F (about 115°C) for general-purpose PC [S3][S4]. Forming temperature lands at 350°F–400°F and Rockwell hardness at M70–M80, both confirmed by the May 2026 plastics guide [S4]. PC is self-extinguishing per the source, but flame behaviour depends on grade: unfilled resin typically meets UL 94 V-2, while a specified flame-retardant grade is needed for V-0 in electrical and transit interiors [S1][S2].
When PC beats acrylic, HDPE, and PETG
Pick PC when impact resistance, optical clarity, and a higher service temperature all matter on the same part. Against acrylic, PC trades polishability and surface hardness for roughly 250× more impact resistance and a 60–80°F higher continuous service ceiling (240°F vs 160–180°F) [S4]. Against PETG, PC holds a 80–100°F service-temp advantage at the cost of more aggressive drying before forming [S4]. Against HDPE, PC sacrifices chemical resistance and a low coefficient of friction for stiffness, optical clarity, and dimensional stability under load [S4].
Do not pick PC when the application is purely chemical, low-load, or cost-driven. HDPE, UHMW, and acetal/Delrin outperform PC on chemical resistance, abrasion, and bearing performance, and they are typically cheaper per pound for industrial wear parts and fluid-contact components [S4]. For a fabricated enclosure that lives indoors, never sees impact, and must be laser-cut cleanly, cast acrylic is usually the smarter buy: it machines cleaner, polishes better, and resists scratching, with the trade-off that it cracks under the kinds of loads PC absorbs without complaint [S4]. For comparison points on tougher engineered enclosures used in process skids, see this field view of mechanical seal selection criteria.
Grade map and what each one is actually for
General-purpose clear PC is the default for machine guards, viewing windows, and structural covers where clarity and impact drive the spec [S2]. FDA-compliant grades are required for direct food contact, medical fluid contact, and pharmaceutical processing equipment, and they must be specified to that standard on the print, not assumed [S2]. Flame-retardant PC (UL 94 V-0 or V-2) is the right pick for electrical enclosures, EV battery housings, and any transit interior where a UL flame rating is contractually required [S2].
Glass-fibre-reinforced PC trades optical clarity for higher stiffness, dimensional stability, and load-bearing capacity, and is the right answer for structural components that must hold tight tolerances under sustained load [S2]. UV-stabilized grades are engineered to resist yellowing and embrittlement under sustained sunlight exposure and are the correct choice for outdoor enclosures, transit glazing, and skylights [S1][S2]. Abrasion-resistant (surface-coated) PC is used for viewing windows and machine guards that see regular wiping or contact, because uncoated PC is, frankly, soft: its scratch resistance is poor compared with most engineering plastics [S1][S2]. Bullet-resistant PC laminate is a multi-layer construction rated for security barriers, ATM windows, and protective transit components, and is sold as a system, not a single sheet [S2].
Machining protocol: feeds, cooling, annealing
PC is gummy under heat and crack-prone under residual stress, so the protocol is sharp tooling, controlled chip evacuation, light passes, and a post-machining anneal where the application demands it [S2]. The 2026-07 machining guide recommends standard stock sizes and general-purpose grade where possible, rational tolerance to avoid over-tolerancing the as-machined part, and cutting methods such as CNC milling, CNC routing, and CNC turning over grinders, which generate excessive heat and damage the part [S3].
Drying before any thermoforming step is mandatory: PC must be dried before forming to avoid hydrolysis and bubbled edges [S4]. Drilling, counterboring, and tapping benefit from slow feeds and controlled cooling rather than aggressive material removal, and edge finishing options include flame polishing, machine polishing, and diamond-tool finishing for clear-edge applications [S2]. Annealing is the controlled stress-relief step that prevents micro-cracks from propagating after machining, and it is most often specified for tight-tolerance, optically clear, or load-bearing parts [S2]. PC is poor against strong solvents, so any cutting fluid, adhesive, or cleaning agent must be checked against the resin manufacturer's chemical-resistance chart before use [S3].
Standards and ratings that belong on the print
UL 94 V-0 or V-2 flammability is the most common rating called out for fabricated PC, with the V-0 grade reserved for electrical enclosures, EV battery housings, and transit interiors [S1][S2]. FDA compliance is the relevant designation for food-contact and medical-fluid-contact parts and must be specified against the current FDA food-contact regulation, not just a generic "food grade" label [S2]. For outdoor service, UV-stabilized grades are a hard requirement, since plain PC yellows and embrittles with sustained UV exposure, and the same applies to bullet-resistant parts sold under a tested multi-layer laminate rating rather than a generic thickness claim [S1][S2].
For optical parts, light transmittance around 90% is the published figure for clear PC sheet, and any deviation should be checked against the specific grade's data sheet rather than the generic value [S3]. For fabricated PC used inside industrial PC enclosures and adjacent to process instrumentation, the material's electrical insulation properties (dielectric constant 3.0–3.2, arc resistance 120 s) and its UL temperature index of 120–140°C after glass-fibre reinforcement are the relevant numbers, not the headline impact strength [S1].
Failure modes a spec writer should anticipate
Hydrolysis under high-pressure steam is a hard exclusion: PC is not suitable for parts that will see repeated high-pressure steam cycles, and any hot, humid service should be reviewed against the resin data sheet [S1]. UV-driven yellowing and embrittlement will hit plain PC outdoors within months, and that failure mode is solved by specifying a UV-stabilized grade, not by adding paint after the fact [S1][S2]. Notch sensitivity and poor scratch resistance mean that machined edges, drilled holes, and any wiped surface are crack and scuff initiation sites; the practical answer is generous radii on machined features, abrasion-resistant coating on wiped surfaces, and stress-relief annealing on tight-tolerance parts [S1][S2].
PC has poor chemical resistance to strong solvents and strong alkalis and will craze or crack in contact with them, so chemical compatibility must be checked against the resin manufacturer's chart before any cutting fluid, adhesive, or cleaning agent is approved for production use [S1][S3]. The material is also notch-sensitive in the presence of organic solvents, meaning that a solvent spill near a machined edge can crack a part that would otherwise survive its design load [S1]. For adjacent spec work on instrumentation that may sit inside or alongside a PC enclosure, see this field guide on pressure transmitter selection.
PC is a strong default for general fabrication when impact, clarity, and a 130–147°C thermal ceiling are required, with grade choice driven by the rating, environment, and standard on the print. Two trackable signals for the next buying cycle are the rollout of abrasion-resistant coated grades for high-wipe applications and tighter UV-stabilized specifications for transit and outdoor enclosures, both of which are already standard SKU lines at major North American fabricators as of 2026-08 [S2]. For buyers sourcing PC-heavy enclosures and adjacent components in parallel, this spec-first view of procurement signals in building materials is a useful cross-check on the supply side.