Polycarbonate (PC)
Also: PC, Lexan, Makrolon, Tuffak, Panlite, polycarbonate sheet, machine-grade polycarbonate, bisphenol A polycarbonate, glass-filled polycarbonate, PC/ABS (blend)
Polycarbonate: the tough, clear plastic, with about 30x the notched impact strength of acrylic; cold-bendable, stiff to 130 °C. Scratches; solvents crack it.
Sourcing polycarbonate parts or stock?
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At a glance
| Density | 1.2 g/cm³ (0.043 lb/in³) |
|---|---|
| Tensile strength | 62-66 MPa (9.0-9.5 ksi) at yield |
| Yield strength | 62 MPa (9.0 ksi) tensile yield |
| Hardness | Rockwell M 70 (Rockwell R 118-122) |
| Elongation | 80-120% at break |
| Modulus of elasticity | 2.3-2.4 GPa (0.33-0.35 Msi) tensile |
| Thermal | Tg about 147-150 °C (297-302 °F); amorphous, no melting point; continuous service about 115-125 °C (240-257 °F); HDT about 130-138 °C (265-280 °F) at 1.82 MPa |
| Composition | Bisphenol A polycarbonate, amorphous; UV-stabilized, hard-coated, flame-retardant and 10-40% glass-filled variants |
Typical values, Unfilled, clear general-purpose extruded sheet and machine-grade plate, dry, 23 °C (73 °F). Confirm against the mill certificate and the purchase spec.
- MachinabilityGood
- Machines cleanly with sharp, zero- to positive-rake tools. It is notch-sensitive and stress cracks: use air or plain water rather than solvent- or petroleum-based coolants, avoid heat build-up, and anneal after heavy machining.
- WeldabilityGood
- Solvent bonds with methylene chloride based cements and welds well by ultrasonic, hot-plate, vibration and laser methods. Test adhesives first: some cyanoacrylates, anaerobics and solvent-borne adhesives craze stressed PC.
- FormabilityExcellent
- Sheet bends cold on a brake or roller, line-bends with a strip heater and thermoforms well. Dry the sheet first (about 120 °C, 250 °F, for hours depending on thickness) or absorbed moisture bubbles during heating.
- Corrosion resistanceFair
- Resists water, dilute acids, oils, greases and many aliphatic hydrocarbons. Attacked by alkalis, ammonia and amines, and dissolved or crazed by ketones, esters, aromatic and chlorinated solvents. Hot water above about 60 °C (140 °F) slowly hydrolyzes it, and UV yellows unprotected sheet.
Polycarbonate (PC) is an amorphous, transparent thermoplastic, almost always the bisphenol A type sold as Lexan, Makrolon and Tuffak. Its reason to exist is toughness: a notched Izod impact strength of about 640-850 J/m (12-16 ft-lb/in) at 3.2 mm (1/8") thickness, against about 20-30 J/m for acrylic, with 88-90% light transmission. That makes it the default for machine guards, safety glazing, face shields, lenses, electrical enclosures and clear housings that will be hit, dropped or flexed.
That toughness has conditions. Impact strength falls sharply in thick sections, at sharp notches and after heat aging, and PC is prone to environmental stress cracking: a stressed part in contact with acetone, many solvents and cleaners, anaerobic threadlockers, some cutting fluids or plasticized gaskets can craze and crack. It also scratches easily and yellows in sunlight unless the sheet is UV-stabilized or hard-coated.
For fabrication PC is forgiving. It bends cold, thermoforms well once the sheet is dried, solvent bonds, ultrasonic welds and machines cleanly. It is one of the highest-volume injection molding resins, often blended with ABS (PC/ABS) for tough, cheaper, plateable housings. Choose acrylic instead where optical clarity, scratch resistance and outdoor stability matter more than impact.
Heat treatment
Not heat treated for properties. Anneal machined or bent parts that will see solvents, cleaners or sustained load at about 120-130 °C (250-265 °F), below Tg, holding roughly an hour per 6 mm (1/4") of thickness and cooling slowly. Dry sheet and pellets before forming or molding.
Tempers and conditions
- Clear general-purpose sheet
- UV-stabilized sheet
- Abrasion-resistant hard-coated sheet
- Machine-grade (stress-relieved) plate and rod
- Flame-retardant (UL 94 V-0) grades
- Glass-filled 10-40% (molded)
- Medical and food-contact grades
- Bullet-resisting laminates
Stock forms
- Sheet (clear, tinted, textured)
- Plate
- Rod and tube
- Multiwall and corrugated sheet
- Film
- Molding pellets
- FDM filament
Relative cost
Tier 2 of 5. About 2x HDPE per pound and somewhat more than acrylic; hard-coated, UV-stabilized, flame-retardant and optical grades cost more.
Typical applications
- Machine guards and safety windows
- Face shields, safety glasses and visors
- Electrical enclosures, meter covers and light diffusers
- Clear housings, manifolds and medical device bodies
- Lenses and light pipes (optical grades)
- Glazing, skylights and greenhouse multiwall sheet
- Security and bullet-resisting glazing (laminated)
Process compatibility
How polycarbonate takes each process, and what to specify. Each process links to its own guide and to the shops that do it.
| Process | Rating | Notes |
|---|---|---|
| CNC Machining | GoodGood | Machines cleanly for guards, housings and clear prototypes; control stress and coolant choice to avoid cracking later. |
| CNC Milling | GoodGood | Routes and mills from sheet and plate; leave the protective film on and use single-flute cutters to clear chips. |
| CNC Turning | GoodGood | Clear rod turns well; vapor polishing or diamond turning restores clarity, and flame polishing works less well than on acrylic. |
| Injection Molding | ExcellentExcellent | A top-volume resin for tough and clear parts; dry the resin, run hot molds, and use generous radii to limit molded-in stress. |
| Press Brake Forming | GoodGood | Thin sheet cold-bends on a brake with a generous radius and some springback. The bend holds stress, so keep solvents and cleaners off it. |
| Waterjet Cutting | GoodGood | Cuts sheet and plate cold with a frosted edge and no charring or added stress. |
| Laser Cutting | Not recommendedNot recommended | PC burns rather than vaporizing: the edge chars brown to black and the sheet discolors. Rout, saw or waterjet instead. Can polycarbonate be laser cut? |
| FDM 3D Printing | FairFair | Prints on hot-end, heated-chamber machines and warps without one; printed PC is tough but weaker across layers than molded or machined PC. |
| Vibratory Finishing | FairFair | Deburrs opaque or non-cosmetic parts; clear parts come out hazy. |
| Bead Blasting | FairFair | Gives an even frosted finish on clear parts for diffusers and non-glare windows. |
| Plating | PoorPoor | Straight PC plates poorly; plating-grade ABS or PC/ABS is the route to a plated plastic part. Vacuum metallizing works for reflectors. |
Compare polycarbonate
Design and sourcing tips
- Specify UV-stabilized or hard-coated sheet for anything outdoors or exposed to abrasion; plain PC yellows in sunlight and scratches easily.
- List every chemical the part will touch, including cleaners, threadlockers and gaskets. Keep stress low near those contacts and ask for annealing after machining.
- Radius inside corners and avoid sharp notches: PC is tough in bulk and brittle at a notch.
- Allow for thermal expansion of about 65-70 um/m·K in frames and glazing channels, and use oversized holes with shoulder washers on bolted sheet.
- On clear machined parts, say which faces must be optically clear; vapor polishing or diamond turning then adds cost only where it is needed.
- Do not specify laser cutting; rout, saw or waterjet PC.
Frequently asked questions
- Is polycarbonate stronger than acrylic?
- In impact, far stronger: a notched Izod of about 640-850 J/m against about 20-30 J/m for acrylic, which is why PC is used for guards and safety glazing. In tensile strength the two are similar, and acrylic is actually a little stiffer, harder, more scratch-resistant, clearer and more stable in sunlight. Choose PC for impact, acrylic for optics and outdoor clarity.
- Can polycarbonate be laser cut?
- Not well. CO2 lasers burn polycarbonate rather than vaporizing it cleanly, leaving a brown to black, weak edge, a discolored surface and unpleasant fumes. Cut PC by CNC routing, sawing or waterjet. If laser cutting is the plan, acrylic is the clear plastic to choose.
- Why does polycarbonate crack?
- Usually environmental stress cracking. A part carrying stress, from machining, bending, a press fit or a bolt, meets a chemical that attacks PC, such as acetone, many solvents and cleaners, anaerobic threadlockers or plasticized gaskets. Fine crazes form and grow into cracks. Anneal after fabrication, keep stress low and check chemical compatibility.
- Can polycarbonate be bent cold?
- Yes. Thin PC sheet can be cold-bent on a press brake or rolled to a curve without heat, which acrylic cannot do. Use a generous bend radius, expect some springback, and remember the bend holds residual stress, so keep solvents away from it. Thicker sheet is dried and bent hot with a strip heater.
- Is polycarbonate UV resistant?
- Plain PC yellows and loses toughness after long sun exposure. Outdoor sheet is UV-stabilized, usually with a coextruded UV-protective layer on one or both faces, which must face outward when installed. Acrylic weathers better where impact is not a concern.
Processes that commonly use it
Related materials
Where to verify these values
- SABIC Lexan resin and sheet data sheets
- Covestro Makrolon and Plaskolite Tuffak data sheets and fabrication guides
- ASTM D3935; ASTM D638, D256 (Izod impact) and D648 test methods
