Can Polycarbonate Be Injection Molded? The Complete Guide

Can Polycarbonate Be Injection Molded?

Short answer: Absolutely. In fact, polycarbonate (PC) is one of the most popular thermoplastics for injection molding. And for good reason. This engineering plastic combines incredible strength with optical clarity. Which makes it perfect for everything from safety glasses to car headlights.

Но вот в чем дело:

While polycarbonate CAN be injection molded, it’s not exactly a walk in the park. This material has some quirks that can make or break your project.

Именно поэтому я подготовил это полное руководство.

Today, as a professional PC injection molding manufacturer, I will share:

• Why polycarbonate is perfect for injection molding (and when it’s not)
• The exact process parameters you need to get right
• Common problems and how to avoid them
• Real-world applications that prove PC’s worth
• Cost considerations that might surprise you

Давайте окунемся с головой.

Why Polycarbonate Works So Well for Injection Molding

Дело вот в чем:

Polycarbonate is a thermoplastic polymer. That means it can be melted, shaped, and cooled repeatedly without losing its properties.

This makes it PERFECT for injection molding.

But that’s just scratching the surface.

Polycarbonate brings some serious advantages to the table:

Impact Resistance That’s Off the Charts

We’re talking 250 times stronger than glass. And 30 times tougher than acrylic.

I’ve seen polycarbonate parts survive drops that would shatter other plastics into a million pieces.

Crystal Clear Transparency

Unlike many strong plastics, polycarbonate can be as clear as glass. Which is why it’s the go-to material for safety glasses and face shields.

Temperature Resistance

Polycarbonate laughs at extreme temperatures. It performs well from -40°F to 280°F (-40°C to 138°C).

Устойчивость размеров

Once molded, polycarbonate parts hold their shape. Even under stress. Even over time.

The Injection Molding Process for Polycarbonate

Now, let’s break down exactly how polycarbonate injection molding works.

(Spoiler: It’s more complex than you might think.)

Шаг 1: Подготовка материалов

Прежде всего:

Polycarbonate is hygroscopic. That’s a fancy way of saying it absorbs moisture like a sponge.

And moisture is the enemy of good injection molding.

So before anything else, you need to dry those PC pellets. We’re talking moisture content below 0.02%.

Skip this step? You’ll end up with parts full of bubbles, streaks, and weak spots.

Step 2: Heating and Melting

Here’s where things get toasty.

Polycarbonate needs HIGH temperatures to melt properly. We’re talking 270°C to 320°C (518°F to 608°F).

The material has high viscosity when melted. Think honey vs. water. This thick consistency means you need serious heat and pressure to get it flowing.

Step 3: Injection

Once melted, the polycarbonate gets forced into the mold at high pressure.

And when I say high pressure, I mean it. We’re often looking at 80-120 MPa of injection pressure.

Speed matters too. You need to inject quickly to prevent the material from cooling and solidifying before filling the mold.

Step 4: Cooling and Ejection

After injection, the part needs to cool. But here’s the tricky part:

Polycarbonate has a high shrinkage rate. About 0.5-0.7% as it cools.

Smart mold designers account for this. They make molds slightly oversized so the final part comes out just right.

Critical Process Parameters You Can’t Ignore

Let me be straight with you:

Get these parameters wrong, and you’ll waste time, money, and materials.

Barrel Temperature Zones:

• Feed zone: 280-300°C
• Compression zone: 290-310°C
• Metering zone: 300-320°C

Температура формы:
80-120°C (176-248°F)

Higher mold temps = better surface finish and reduced stress. But also longer cycle times.

Injection Speed:
Fast. Really fast. We’re talking 50-150 mm/s.

Why so fast? Remember that high viscosity I mentioned? Speed helps overcome it.

Holding Pressure:
50-80% of injection pressure, held for 5-15 seconds.

This prevents sink marks and ensures proper packing.

Распространенные проблемы (и способы их устранения)

Even experienced molders run into issues with polycarbonate. Here are the big ones:

Problem 1: Splay Marks and Streaks

These ugly surface defects usually mean one thing: moisture.

The Fix: Double-check your drying process. Consider using a dehumidifying dryer for at least 4 hours at 120°C.

Problem 2: Bubbles and Voids

Internal bubbles weaken parts and look terrible in transparent applications.

The Fix: Lower your injection speed slightly and increase holding pressure. Also check for moisture (again).

Problem 3: Warping

Parts coming out twisted or bent? That’s usually uneven cooling.

The Fix: Ensure uniform mold temperature. Consider adding cooling channels if needed.

Problem 4: Short Shots

When the mold doesn’t fill completely, you’ve got problems.

The Fix: Increase injection pressure, speed, or melt temperature. Sometimes all three.

Advanced Techniques for Better Results

Want to take your polycarbonate molding to the next level? Try these pro techniques:

Rapid Heating & Cooling (RH&C)

This technique heats the mold just before injection, then rapidly cools it.

Result? Mirror-finish surfaces with zero weld lines.

Water-Assisted Injection Molding

Perfect for large, hollow parts. High-pressure water helps create uniform wall thickness.

Compression Injection Molding

Eliminates sink marks in thick-walled parts. The mold closes after partial filling, compressing the material.

Real-World Applications That Prove PC’s Worth

Theory is great. But let’s look at what polycarbonate injection molding can actually do:

Автомобильная промышленность

• Headlight lenses (withstand impacts and UV exposure)
• Interior trim pieces
• Instrument clusters

Медицинские приборы

• Surgical instruments (can be sterilized repeatedly)
• Drug delivery devices
• Diagnostic equipment housings

Электроника

• Phone cases
• LED light diffusers
• Computer components

Safety Equipment

• Face shields
• Safety glasses
• Protective helmets

Each application leverages polycarbonate’s unique properties. And injection molding makes mass production economically viable.

Cost Considerations and ROI

Давайте поговорим о деньгах.

Polycarbonate costs more than basic plastics like polypropylene or ABS. We’re looking at $2-4 per pound vs. $1-2 for commodity plastics.

Но вот в чем дело:

The superior properties often justify the cost. Especially when you factor in:

• Longer part life (fewer replacements)
• Better performance (fewer failures)
• Premium product positioning

Mold costs for polycarbonate can be higher too. The high processing temperatures and pressures require robust tooling.

But if you’re making thousands of parts? The per-unit cost drops dramatically.

When NOT to Use Polycarbonate

Look, polycarbonate isn’t always the answer.

Skip it if:

• Chemical resistance is critical (PC doesn’t love certain solvents)
• You need the absolute lowest cost
• UV exposure is extreme without protection
• Continuous use temperature exceeds 140°C

For these situations, consider alternatives like PEEK, PPS, or even modified acrylics.

Design Tips for Injection Molded Polycarbonate Parts

Good design makes molding easier and parts better. Here’s what works:

Толщина стенок
Keep it uniform. 1-3.5mm works best. Variations cause warping and sink marks.

Углы наклона
Minimum 1-2 degrees. More is better for easy ejection.

Radii and Fillets
Sharp corners = stress concentration. Use generous radii (at least 0.5x wall thickness).

Ribs and Bosses
Keep rib thickness at 50-60% of wall thickness. Prevents sink marks.

Контроль качества и тестирование

You can’t just mold parts and ship them. Quality control is crucial.

Key tests for polycarbonate parts:

• Dimensional verification (are parts within tolerance?)
• Impact testing (especially for safety applications)
• Optical clarity measurement (for transparent parts)
• Stress testing (check for internal stresses)

Pro tip: Use polarized light to check transparent parts for stress. Internal stress shows up as rainbow patterns.

Итоги

Can polycarbonate be injection molded? Absolutely. And when done right, it produces parts with an unbeatable combination of strength, clarity, and precision.

But success requires attention to detail. From proper material drying to precise temperature control, every parameter matters.

The good news? Master these techniques, and you’ll be producing high-quality polycarbonate parts that outperform the competition.

Whether you’re making safety equipment, automotive components, or medical devices, polycarbonate injection molding opens up possibilities that other materials simply can’t match.

Just remember: respect the material’s unique requirements, and it’ll reward you with exceptional parts.

Ready to start your polycarbonate injection molding project? Now you’ve got the knowledge to do it right.