Can PLA Be Microwaved? Is it Safe?

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There are different types of materials out there for 3D printing. However, PLA is now rapidly becoming the filament of choice for many people who love 3D printing.

However many people who use it for food utensils want to know if it food safe for microwaves?

microwave

Is PLA Microwave-safe?

PLA is not microwave-safe. Microwaves will most definitely soften or melt your PLA. Although microwaves interact with water molecules or metallic ions, a temperature higher than 70 degrees C will soften your PLA. As you can imagine, it is very difficult to control the temperature in a microwave, so you don’t want to take this risk.

There is anecdotal evidence that if you microwave transparent PLA with a glass of water, the water will absorb all the microwaves and the PLA itself will not heat up.

However, this does not take into consideration whether your PLA part has absorbed any atmospheric moisture, and this has not been tested with colored PLA.

ABS and any other filaments are not microwave-safe either. ABS gives off toxic fumes when it heats up.

Is PLA Heat Resistant?

As a general rule, PLA is a lot less heat-resistant than many other 3D printing filaments out there and its resistance to high temperatures is virtually the lowest of any 3D printing material available today.

In fact, the average glass transition temperature of these filaments tends to fluctuate between 60C to 65C (140F to 150F). This is why it is not considered to be the filament of choice not just for internal high temperature environments but also harsh outdoor conditions. 3D printed parts for outdoor use are commonly the sole domain of PETG filament.

Is PLA food-safe?

PLA stands for polylatic acid. Polylactic acid is made of a chain of lactic acid molecules. Lactic acid can be found in foods, but that does not mean you can go eat PLA filament next time you are hungry! PLA filaments are not pure PLA, and contain many additives like colors and other chemicals.

After all, they’re not manufactured in a food-safe environment!

The 3D printing process may also add unwanted chemicals to your final printed part.

Some manufacturers may state on their filament that it is food-safe, but even then, those are best for single uses.

You’ll find some people who say that PLA is food-safe, and others who say you should avoid it. My take is that while PLA can be food-safe, it’s best to not store any food in PLA.

The main reason for this is because parts 3D printed in PLA are porous. Water and food particles can get stuck in these pores and become a breeding ground for all sorts of nasty bacteria.

To kill bacteria, you’ll need to use heat or an acid. Since it’s PLA we’re talking about here, heat is out of the question: the moment you try to disinfect PLA with heat, your part will deform and melt.

You could use an acid like vinegar to try and kill the bacteria, but the PLA would absorb all the vinegar flavor and aroma and ruin it for use with any food.

If you must use PLA with food…

If you must use a PLA container or plate with food, use it for dry, large pieces like chips or crackers. These are relatively inert and can be stored anywhere. There’s also little to no moisture that can get trapped in the pores.

Even then, small crumbs may get stuck in the pores and end up becoming a breeding ground for bacteria due to moisture in the atmosphere.

If you must use PLA, use it once and then recycle it or throw it out.

Conclusion

PLA is definitely not safe for the microwave, and it’s definitely not safe for food. Stick to food-safe utensils for food and drink!

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