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Policarbonato

PC·Polycarbonates·Amorphous

Polycarbonate (PC) is the engineering polymer with the most extreme combination of properties: transparent as glass yet up to 250 times more impact-resistant than glass, tolerating continuous temperatures up to 135°C, and injectable with optical detail. It is the material of CDs/DVDs, reusable bottles, motorcycle helmets, bulletproof glazing, automotive headlights and thousands of products where transparency is non-negotiable and impact resistance is mandatory.

But that combination comes at a price: it is highly hygroscopic (moisture degrades it catastrophically), sensitive to stress cracking from common chemicals, and the BPA shadow has followed it for 20 years even though regulators (FDA, EFSA) still approve it for food contact. Here we have compiled the reference ranges from the PDS, plus the questions that come up over and over on the shop floor: how to dry it correctly, why it yellows in sunlight, when PC/ABS makes sense, and why automotive LED headlights last as long as they do.

Share your experience in the comments — ranges vary by optical/medical/industrial grade, and collective discussion is what gets us out of trouble on the floor.

The ranges shown in these data tables were compiled by the MVPS team from various parameter sheets and literature, integrating the lower and upper limits for each material type.

This information must be carefully reviewed when developing injection molding processes. Final ranges and processing tolerances are the responsibility of the engineer in charge.

These ranges are not recommended for developing specific process tolerances. MVPS always recommends requesting and consulting the supplier's data sheet.

General Properties

Chemical StructureAmorphous
Specific Gravity (Density)1.2:1
L/D Ratio15 – 20:1
Compression Ratio2 – 3:1
Tonnage Factor6.18 – 7.72kN/cm²
Thermal Diffusivity0.1496mm²/s
Max Shear Rate40,0001/s
Shrinkage0.5 – 0.7%
Regrind20%
Heat Deflection (HDT) @ 1.82 MPa141°C
Glass Transition (Tg) @ 10°C/min146°C
Vicat Softening @ 50N135°C

Drying

Drying Temperature110 – 121°C
Drying Time2 – 4h
Recommended Moisture0.02%
Recommended Dryer TypeDesiccant
Dew Point-40°C

Temperatures

Melt277 – 338°C
Nozzle249 – 321°C
Front291 – 321°C
Middle271 – 302°C
Rear249 – 282°C
Demolding82 – 110°C
Mold (Cooling)66 – 99°C
Feed Throat35 – 79°C

Processing

Back Pressure3.1 – 10.3bar
Screw Speed40 – 70RPM
Injection SpeedLow – Medium
Barrel Occupancy30 – 80%
Injection Pressure1,200 – 1,450Pbar
Holding Pressure300 – 1,160Pbar
Cushion6.4 – 12.7mm

Mold

Runner Diameter4.06 – 9.14mm
Gate Diameter1.02 – 2.03mm
Gate Area0.81 – 3.24mm²
Wall Thickness1.02 – 4.57mm

Venting

Depth (Vent Depth)0.0254 – 0.0508mm
Land (Vent Land)0.762 – 1.52mm
Width (Vent / Clearance)4.06 – 12.7mm
Relief (Relief Channel)0.2032 – 0.4064mm

Frequently asked questions

Polycarbonate is an amorphous engineering thermoplastic synthesized from Bisphenol A (BPA) + phosgene (or diphenyl carbonate in modern phosgene-free processes). Its rigid aromatic structure delivers an unusual mix: 88% optical transparency, extreme impact resistance (10–30× higher than PMMA, 250× higher than common glass), HDT of 130–140°C and a glass transition temperature (Tg) of ~150°C. Density ~1.20 g/cm³.
Short answer: yes for general adult use, no for infants. FDA and EFSA consider PC safe for food contact at the BPA migration levels measured in finished products. But the FDA banned PC with BPA in 2012 for baby bottles, sippy cups and infant-formula packaging as a regulatory precaution. For those applications, Tritan (copolyester) or PP is used. For reusable adult containers, bottled water, jugs, or durable utensils, PC remains legal and dominant.
UV radiation degrades the carbonate group (C=O–O), releasing CO₂ and producing yellow-tinted products. Without protection, an outdoor part yellows visibly in 6–12 months. Solutions: grades with built-in UV stabilizers or, better still, a siloxane UV hard-coat (what automotive headlights use, lasting 8–10 years before noticeable yellowing). For indoor use under fluorescent/LED lighting, standard UV-stabilized grades are enough.
PC is highly hygroscopic. At injection temperatures (~290–310°C), absorbed moisture reacts with the polymer chain via hydrolysis, breaking it. Moisture of 0.02% (200 ppm) or less is critical. Always desiccant, 120–130°C for 3–6 hours, dew point ≤ –40°C. Injecting wet PC gives you silver streaks, loss of transparency, a 50–80% drop in impact and bubbles. It is the number-one mistake of PC newcomers.
PC has moderate sensitivity to environmental stress cracking (ESC): under mechanical stress + certain chemicals (alcohols, hydrocarbons, dilute acids), fine cracks appear and progress quickly. Solutions: (1) post-mold annealing at 125–135°C for 1–4 h releases residual stress, (2) avoid contact with aggressive cleaners (isopropanol, acetone, gasoline), (3) use chemical-resistant grades for demanding applications, (4) be careful with FR (flame-retardant) grades — they usually have lower ESC resistance.
Main tradeoff: PMMA wins on optical clarity (92% vs 88%), UV resistance (does not yellow), surface hardness (more scratch resistant), cost (30–50% cheaper). PC wins on impact (10–30× more, practically unbreakable), thermal tolerance (140°C vs 80°C), thermoforming ease, and broader chemical resistance. Rule of thumb: if the main risk is breaking → PC. If the risk is scratching or yellowing → PMMA. Safety lenses → PC. Jewelry display cases → PMMA.
PC beats ABS in impact (especially at low temperature), HDT (130 vs 80°C), transparency, and scratch resistance. ABS beats PC in processing ease, chemical resistance (PC is hydrocarbon-sensitive), cost (~40% cheaper) and moisture tolerance without degradation. The PC/ABS blend combines both: ~50% of pure-PC impact, better processability, higher HDT than ABS alone. It is the backbone of electronics housings (Dell, HP, Lenovo), automotive interiors (console, panels) and motorcycle helmets.
The PDS marks 79–121°C — high compared to commodities. Hotter (95–115°C) = better gloss, less residual stress, better optical detail reproduction, but longer cycle. Cooler (80–90°C) = short cycle but higher stress cracking risk and worse surface. For optics/lenses: 110–120°C. For non-cosmetic structural parts: 90–100°C. Never below 80°C — you freeze flow and generate internal stress that cracks later.
The PDS marks 20% as the maximum. Each reprocessing cycle slightly degrades molecular weight and transparency. For critical optical parts (lenses, headlights) many OEMs forbid all regrind. For structural parts, up to 20% is safe provided the material is well-dried before reprocessing — regrind absorbs moisture from ambient air between operations. If the part is transparent, expect a slight yellow tint after the second recycle.
Three reasons: (1) costly raw material — BPA + phosgene synthesis requires complex infrastructure with few global producers (Covestro, SABIC, Trinseo, Mitsubishi Engineering Plastics, Idemitsu); (2) high processing energy — 290–310°C vs 220°C for ABS, mandatory intensive drying; (3) certifications — optical, medical and aerospace grades require costly validations. Result: commodity PC costs 2–3× more than ABS, and premium grades (optical Makrolon, Lexan EXL impact) can cost 4–6×.

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