Polycarbonate (PC) Injection Molding: A Buyer's Guide

When a part has to take a hit, stay clear, or tolerate heat that would soften cheaper plastics, polycarbonate is often the answer. It’s the material behind safety glazing, headlamp lenses, and rugged equipment housings. It costs more than commodity resins and is more demanding to mold, but for the right application it earns its place. This guide covers PC from a buyer’s standpoint, as part of the material selection guide.

What Polycarbonate Is

Polycarbonate (PC) is an engineering thermoplastic known for an unusual combination of high impact strength and optical clarity, along with good heat resistance and dimensional stability. You’ll see it under brand names like Lexan and Makrolon. It’s frequently used on its own and also blended—PC/ABS being a common blend that lowers cost and eases processing while keeping much of PC’s toughness.

Why Buyers Choose PC

Characteristic	What it means for your part
Very high impact strength	Resists breakage even in thin sections—a standout property
Optical clarity	Can be molded transparent, suiting lenses and covers
Good heat resistance	Tolerates higher temperatures than ABS or PP
Dimensional stability	Holds shape and size well under load and heat
Flame-retardant grades available	Useful for electrical and electronic housings

That impact-plus-clarity-plus-heat profile is why PC dominates applications like safety shields, lighting, and demanding enclosures.

Where PC Falls Short

• Scratches easily. Bare PC has poor surface hardness, so clear parts that must resist scratching usually need a hard coat.
• Chemical sensitivity and stress cracking. PC is attacked by certain chemicals and solvents and can stress-crack, which matters for parts exposed to cleaners, fuels, or some adhesives.
• Notch sensitivity. Despite its toughness, sharp internal corners can concentrate stress, so generous radii matter in design.
• Higher cost and more demanding processing than commodity resins, including a real need for thorough drying.

When clarity isn’t needed and cost matters, a PC/ABS blend or another engineering resin may be the better trade.

Common Applications

PC is used for safety glazing and face shields, automotive lighting and lenses, electrical and electronic housings (often flame-retardant grades), medical devices, machine guards, and rugged equipment enclosures—anywhere impact resistance, clarity, or heat tolerance is the deciding factor.

What Buyers Should Know About Molding PC

• Drying is critical. PC is hygroscopic and must be dried thoroughly; molding it wet degrades the material and causes cosmetic and strength problems. This is a fair question for a prospective supplier.
• It molds hot. PC runs at higher melt and mold temperatures than commodity resins, which is part of why it’s more demanding and why supplier process control matters.
• Design out sharp corners. Because PC is notch-sensitive, internal radii and smooth transitions help it perform—an area the DFM guide covers.
• Clarity raises the bar on finish and cleanliness. Transparent PC parts show every flaw, so cosmetic surfaces, mold finish, and process cleanliness all matter more.

Typical Processing Window

PC is more demanding to run than commodity resins, and the window shows why: it needs thorough drying and a hot barrel and mold. The ranges below are illustrative for unfilled PC:

Parameter	Typical range (unfilled PC)
Drying	~110–120 °C for 2–4 h (essential; wet PC degrades and causes splay)
Melt (barrel) temperature	~280–320 °C
Mold temperature	~80–110 °C
Mold shrinkage	~0.5–0.7%

Illustrative ranges for unfilled grades, drawn from general industry processing references and a factory parameter table—not a substitute for the specific grade’s datasheet. Actual settings depend on grade, geometry, and machine, and filled grades differ (notably lower, more directional shrinkage). Confirm with the resin datasheet and your molder.

How PC Compares

Against ABS, PC offers far higher impact strength, clarity, and heat resistance, at higher cost and with harder processing. Against high-performance polymers, PC is more affordable and easier but less capable thermally and chemically. PC/ABS blends are the common middle ground. Match the choice to whether impact, clarity, or heat is the real driver—see the material selection guide.

This is an independent buyer resource, not materials-engineering advice. Confirm the right PC grade, blend, and any coatings with the datasheet and your supplier for your application.

Buyer FAQs

What is polycarbonate used for in injection molding?

Polycarbonate is used where impact strength, optical clarity, or heat resistance is the deciding factor: safety glazing and face shields, automotive lighting and lenses, electrical and electronic housings (often in flame-retardant grades), medical devices, machine guards, and rugged enclosures. It’s chosen when cheaper plastics can’t survive the impact, temperature, or transparency requirement.

What are the disadvantages of polycarbonate?

Bare PC scratches easily and often needs a hard coat for clear parts; it’s sensitive to certain chemicals and can stress-crack; and it’s notch-sensitive, so sharp internal corners concentrate stress. It also costs more and is more demanding to mold than commodity resins, including a strict drying requirement. For non-clear, cost-sensitive parts, a PC/ABS blend or another resin may be a better fit.

Why does polycarbonate need to be dried before molding?

PC is hygroscopic—it absorbs moisture from the air—and molding it wet causes the polymer to degrade, which shows up as cosmetic defects and reduced strength. Thorough drying to the resin maker’s specification is essential, which is why a molder’s drying discipline matters for PC parts and is a reasonable thing to confirm.

What is PC/ABS and when is it used?

PC/ABS is a blend of polycarbonate and ABS that keeps much of PC’s toughness and heat resistance while lowering cost and easing processing compared with full PC. It’s widely used for enclosures and automotive interior parts where you want better performance than ABS alone but don’t need the full capability—or full cost—of pure polycarbonate.