What Causes PLA to Become Brittle? (Solutions and Advanced Tips)


As an Amazon Associate, I earn from qualifying purchases.

PLA filament, a cornerstone in the world of 3D printing, is renowned for its versatility and eco-friendliness. Derived from renewable resources, it’s a go-to choice for many printing projects.

However, a common hurdle I’ve encountered, and perhaps you have too, is its tendency to become brittle. This brittleness can turn a promising print into a frustrating challenge.

Understanding what causes PLA to become brittle? Is not just about fixing a current problem; it’s about foreseeing and preventing future printing mishaps. Let’s delve into the world of PLA, unravel its complexities, and explore how to maintain its integrity for flawless prints.

Read More:

Main Causes of PLA Brittleness

1. Moisture Absorption

PLA filament, despite its robust appearance, has a vulnerability – moisture. It’s like a sponge in humid environments, absorbing moisture from the air. This absorption isn’t just a surface-level issue; it penetrates deep into the filament.

The science behind this is simple yet impactful. When PLA absorbs moisture, it undergoes a chemical change, leading to hydrolysis. This process breaks down the polymer chains, weakening the filament’s structure.

The result? A filament that once was strong and flexible becomes brittle and prone to snapping. It’s a silent transformation that can ruin prints unexpectedly.

moisture.jpg | 3D Gear Guide

Left: PLA that absorbed humidity.
Right: PLA filament, properly preserved

2. Mechanical Stress from Spooling

Ever noticed how a coiled garden hose tends to retain its shape? PLA filament behaves similarly. When spooled for long periods, PLA develops memory of this coiled state. This memory isn’t just a physical trait; it’s a point of stress.

Each time the filament is uncoiled and straightened for printing, it undergoes mechanical stress. Over time, this stress accumulates, creating micro-fractures and weak points. These stress points are like ticking time bombs in your filament, ready to cause breaks and failures mid-print.

3. Quality of Filament

Not all PLA is created equal. Variations in manufacturing processes play a significant role in filament quality. High-quality PLA uses premium materials and undergoes rigorous quality checks, ensuring uniformity and strength.

On the flip side, low-quality PLA often contains impurities and inconsistent particle sizes, making it more susceptible to brittleness. These subpar filaments might seem like a bargain, but they can cost you more in failed prints and frustration.

4. Environmental Factors

PLA isn’t a fan of extreme temperatures or sunbathing. Temperature fluctuations, especially exposure to high heat, can cause thermal degradation. This degradation alters the filament’s physical properties, leading to brittleness.

Similarly, UV exposure is another environmental villain for PLA. Sunlight can break down the chemical bonds in PLA, leading to discoloration and a loss of structural integrity. It’s like leaving plastic toys out in the sun; they fade and become brittle over time. The same fate befalls PLA filament exposed to UV light.

Identifying Brittle PLA Filament

1. Spotting the Signs

When PLA goes rogue and turns brittle, it doesn’t keep it a secret. Visually, you might notice the filament has lost its usual sheen, looking duller than when it was new. It’s like comparing a fresh piece of pasta to one that’s been sitting out too long – the difference is clear.

But the real test is in the handling. Brittle PLA tends to snap with minimal force. It’s like bending a dry twig; you feel no resistance before it breaks.

2. Testing Filament Integrity

To really get to the heart of the matter, try the bend test. Take a small section of your filament and gently bend it. Healthy PLA should show some flexibility, bending a bit before breaking. If it snaps instantly without that give, you’re dealing with brittleness.

Another method is the sound test. When you unspool the filament, listen closely. If you hear a series of tiny cracks or pops, that’s the sound of a brittle filament, not unlike stepping on thin ice. These simple tests can save you from the disappointment of a failed print due to brittle filament.

Preventive Measures and Storage Solutions

1. Storing PLA Filament Right

Storing PLA filament isn’t rocket science, but it does need some attention. The key is to keep it away from its arch-nemesis: moisture. I’ve found that airtight containers are a lifesaver.

They’re like mini fortresses, keeping the humidity at bay. Toss in a few packets of desiccants, those little silica gel packs, and you’ve got yourself a dry haven for your filament.

But it’s not just about keeping it dry; temperature matters too. You want to store your filament in a cool, stable environment.

Think of it like storing wine – you wouldn’t leave it out in the sun, right? The same goes for PLA. A consistent, moderate temperature keeps it in prime condition.

2. Handling PLA with Care

Handling PLA filament is all about reducing stress – not your stress, but the filament’s. When you’re loading it into the printer, avoid forcing it to straighten out too much. It’s like coaxing a cat into a bath; gentle persuasion works better than force.

Also, when you’re done printing, don’t just leave the filament hanging out. Wind it back onto the spool, nice and easy. This way, you avoid unnecessary tension and prevent it from developing a mind of its own – like unspooling or getting tangled.

Remember, a little care in handling goes a long way in keeping your PLA filament from turning brittle.

3. Drying Techniques

When PLA gets brittle, it’s often a moisture issue. The solution? Dry it out. Filament dryers are like spas for your filament, gently coaxing the moisture out without damaging it.

sunlu filament dryer.jpg | 3D Gear Guide

If you don’t have a dryer, an oven can be a makeshift fix. But remember, it’s a delicate process. For PLA, keep the temperature around 45°C (113°F). It’s like slow-roasting to perfection – too hot and you’ll ruin it.

Duration matters too; a few hours should do the trick, but keep an eye on it. It’s about finding that sweet spot where the moisture evaporates without warping the filament.

4. Mechanical Stress Reduction

Reducing mechanical stress on PLA is all about the art of spooling and feeding. First, check the spool tension. It shouldn’t be too tight or too loose – think of tuning a guitar string.

When feeding the filament into the printer, avoid sharp bends or twists. It’s like guiding a thread through a needle – a smooth, gentle approach works best.

And when you’re done printing, wind the filament back carefully. It’s these small steps that prevent stress build-up, keeping your PLA strong and ready for the next print job.

If you are a Prusa i3 Mk3 user, this video will helpful for you.

Advanced Tips and Tricks

1. Selecting High-Quality Filament Brands

Choosing the right PLA filament brand is like picking the perfect apple; it makes all the difference. Look for brands with a reputation for consistency and quality. A good filament should have uniform diameter, minimal impurities, and come vacuum-sealed with desiccant.

I’ve learned that paying a bit more upfront for a reputable brand saves time and money in the long run. It’s not just about the print quality; it’s about avoiding the headache of dealing with brittle filament.

2. DIY and Creativity

The 3D printing community is a goldmine of creative solutions. One DIY fix I’ve seen involves rejuvenating brittle filament by using homemade filament dryers – think repurposed food dehydrators or even carefully monitored ovens.

Another trick is to use homemade spool holders that reduce tension and prevent the filament from unspooling too quickly. These community-driven solutions are not just about fixing problems; they’re about enhancing the entire 3D printing experience with a touch of ingenuity and resourcefulness.


Wrapping it up, we’ve journeyed through the twists and turns of PLA filament care. From understanding its brittleness causes like moisture absorption and mechanical stress to exploring storage solutions and drying techniques, we’ve covered the essentials.

Remember, the key to successful 3D printing lies in choosing quality filament and handling it with care. Embrace the community’s innovative solutions, and don’t shy away from experimenting with DIY fixes.

By following these best practices, you’ll not only enhance your printing experience but also extend the life of your PLA filament. Here’s to many more successful prints with strong, reliable PLA!

Share post:


More like this

How to Change Filament During Print?

3D printing, a realm where creativity meets technology, has...

How to Copy a Key with a 3D Printer?

3D printing technology has revolutionized how we create and...

How to 3D Print Something Without a 3D Printer

3D printing, a marvel of modern technology, has transformed...

How to Assemble a 3D Printer (Ender 3 V2 Example)

Embarking on the journey of assembling the Ender 3...

By continuing to use the site, you agree to the use of cookies. more information

The cookie settings on this website are set to "allow cookies" to give you the best browsing experience possible. If you continue to use this website without changing your cookie settings or you click "Accept" below then you are consenting to this.