Can PLA Plastic Be Injection Molded? The Complete Guide

Can PLA Plastic Be Injection Molded?

Here’s the short answer: Yes, Polylactic Acid (PLA) plastic can be molded using the injection molding process. This is a normal step in the process for this kind of biodegradable polymer.

In fact, PLA is becoming one of the most popular materials for injection molding in 2025. And for good reason.

But here’s the thing:

While PLA can definitely be injection molded, there are some specific tricks you need to know to get it right.

As a professional PLA injection molding manufacturer, that’s exactly what I’m going to show you in this guide.

You’ll learn:

Why PLA is perfect for injection molding (and when it’s not)
The exact conditions you need for successful PLA injection molding
Real-world examples of PLA injection molding in action
Common mistakes to avoid (and how to fix them)

Let’s dive in.

What Makes PLA Perfect for Injection Molding?

First things first:

PLA isn’t just “moldable” – it’s actually GREAT for injection molding.

Here’s why:

1. Lower Processing Temperature = Lower Costs

PLA melts at around 170-230°C.

Compare that to ABS (which needs 220-250°C) or polycarbonate (which requires up to 300°C).

What does this mean for you?

Lower energy costs. Plain and simple.

I’ve seen manufacturers cut their energy bills by 15-20% just by switching from ABS to PLA.

2. It’s Made from Plants (Seriously)

PLA comes from renewable resources like corn starch or sugarcane.

This isn’t just some green marketing fluff.

It actually matters because:

Your customers increasingly care about sustainability
Many industries now REQUIRE eco-friendly materials
You can charge premium prices for “green” products

3. Excellent Flow Properties

Here’s something most people don’t know:

PLA flows beautifully when melted.

This means you can create complex shapes and thin-walled parts that would be impossible with other materials.

The Science Behind PLA Injection Molding

Now, let’s get a bit technical (but I’ll keep it simple).

PLA is what’s called a “semi-crystalline thermoplastic.”

What does that mean?

It means you can actually control whether your final part is:

Amorphous (clear, but less heat-resistant)
Crystalline (opaque, but can handle higher temperatures)

This is HUGE.

Because it means you can tailor the material properties to your exact needs.

Amorphous vs. Crystalline: Which Should You Choose?

Go amorphous when:

Your parts won’t see temperatures above 50°C (120°F)
You need transparency
Faster cycle times are critical

Go crystalline when:

Heat resistance is important
You need maximum strength
The part will be under pressure at elevated temperatures

Step-by-Step: How to Injection Mold PLA Successfully

Let me walk you through the exact process.

Step 1: Dry Your Material (This Is Critical)

PLA is hygroscopic.

Translation: It sucks up moisture from the air like a sponge.

And wet PLA = ruined parts.

Here’s what you need to do:

Dry at 80°C for 2-4 hours
Target moisture content: Below 0.02% (200 ppm)
Use a desiccant dryer with -40°C dew point capability

Pro tip: Get an inline dryer. It’ll save you tons of headaches.

Step 2: Set Your Processing Parameters

Here are the exact settings I recommend:

Melt Temperature: 170-190°C (338-374°F)

Start at 180°C and adjust from there
Higher temps = better flow but more degradation risk

Injection Pressure: 8,000-15,000 psi (55-100 MPa)

Lower than what you’d use for ABS
PLA flows easily, so you don’t need crazy pressure

Mold Temperature: This is where it gets interesting…

For amorphous parts: Keep it cool (10-25°C / 50-75°F)
For crystalline parts: Crank it up (80-105°C / 180-220°F)

Step 3: Optimize Your Cycle Time

Here’s the counterintuitive part:

With crystalline PLA, HIGHER mold temperatures actually help parts eject better.

I know, it sounds backwards.

But trust me on this.

Typical cycle times:

Amorphous PLA: 20-40 seconds
Crystalline PLA: 40-60 seconds (for 1/8″ thick parts)

Real-World Applications: Where PLA Injection Molding Shines

Let me show you where companies are actually using injection molded PLA:

Food Packaging

Remember those clear salad containers at Whole Foods?

Many are now injection molded PLA.

Why? Because PLA is:

FDA approved for food contact
Crystal clear (in amorphous form)
Compostable in industrial facilities

Medical Devices

I recently worked with a medical device company making surgical instrument handles from PLA.

The material is:

Biocompatible
Sterilizable
Strong enough for repeated use

Consumer Products

From phone cases to toys, PLA is everywhere.

One toy manufacturer I know switched entirely to PLA and saw:

30% reduction in material costs
Better customer perception
Easier recycling logistics

Common Problems (And How to Fix Them)

Let’s talk about what can go wrong.

Problem 1: Parts Sticking in the Mold

If using nucleated (crystalline) PLA:

Increase mold temperature above 93°C (200°F)
Extend cooling time
Lower melt temperature as much as possible

If using standard PLA:

Make sure mold temp is below 25°C (75°F)
Check your ejector pin placement

Problem 2: Brittleness

This usually means moisture got into your material.

Solution:

Re-dry your material
Check your dryer’s dew point
Consider a nitrogen blanket on your hopper

Problem 3: Poor Surface Finish

Try these fixes:

Increase injection speed
Bump up mold temperature slightly
Add 10-30% back pressure

PLA vs. Traditional Plastics: The Real Comparison

Let’s get real about how PLA stacks up:

Property	PLA	ABS	PP
Processing Temp	170-230°C	220-250°C	200-250°C
Shrinkage	0.3%	0.5-0.7%	1.0-2.5%
Biodegradable	Yes	No	No
Cost	$$$	$$	$
Heat Resistance	Low-Medium	High	Medium

The takeaway?

PLA isn’t always the cheapest option.

But when you factor in:

Lower energy costs
Marketing advantages
Environmental regulations

It often comes out ahead.

Advanced Tips for PLA Injection Molding

Want to really master PLA injection molding?

Here are some pro-level strategies:

1. Use Nucleating Agents Strategically

Adding nucleating agents can:

Speed up crystallization
Improve heat resistance
Reduce cycle times by 20-30%

But only use them when you need crystalline properties.

2. Consider PLA Blends

Pure PLA has limitations.

But PLA/PC blends? PLA with impact modifiers?

These can give you the best of both worlds.

3. Optimize Your Cooling Channels

PLA’s crystallization behavior means cooling design is CRITICAL.

Consider:

Conformal cooling for complex parts
Multiple cooling zones for thick sections
Separate temperature control for different mold areas

The Economics of PLA Injection Molding

Let’s talk money.

Yes, PLA pellets cost more than commodity plastics.

But here’s what most people miss:

Lower processing costs:

15-20% energy savings
Faster cycle times (for amorphous grades)
Less wear on equipment

Premium pricing potential:

“Eco-friendly” products command 10-30% price premiums
Growing demand in regulated industries
Better brand perception

Total cost analysis:
When you run the numbers, PLA often wins.

Future Trends in PLA Injection Molding

Looking ahead to the rest of 2025 and beyond:

1. Improved Heat Resistance

New PLA grades are pushing heat resistance up to 100°C+.

This opens up automotive and electronics applications.

2. Faster Crystallization

Advanced nucleating packages are cutting cycle times dramatically.

I’m seeing 30-40 second cycles for crystalline parts becoming standard.

3. Better Impact Properties

Impact-modified PLA grades are approaching ABS performance.

Without sacrificing biodegradability.

Your Next Steps

Ready to start injection molding PLA?

Here’s your action plan:

Start with a simple part – Don’t jump into complex geometries right away
Get your drying process dialed in – This is 50% of your success
Work with an experienced material supplier – They can save you weeks of trial and error
Document everything – PLA processing windows are tighter than traditional plastics

The Bottom Line

So, can PLA plastic be injection molded?

Not only can it be done – it’s being done successfully by thousands of manufacturers worldwide.

The key is understanding PLA’s unique properties and adjusting your process accordingly.

With the right approach, PLA injection molding offers:

Excellent part quality
Environmental benefits
Cost competitiveness
Growing market opportunities

The question isn’t whether you CAN injection mold PLA.

It’s whether you can afford NOT to.

Because as environmental regulations tighten and consumers demand sustainable products, PLA injection molding is moving from “nice to have” to “must have.”

Start small. Learn the process. And position yourself for the sustainable manufacturing revolution that’s already underway.

Remember: Can PLA plastic be injection molded? Absolutely. And now you know exactly how to do it right.