What Solvent Will Dissolve PLA Plastic/filament?

PLA is the most popular filament material for FDM 3D printers, and most enthusiasts use it for various printing purposes. Thus, it would be best if you learn how to work with it.

Whether you want to smooth, remove, or glue printed pieces or clean the nozzle from the residual filament, knowing how to dissolve PLA can come quite handy.

Many chemicals can dissolve polylactic acid and with various solubility levels. Here we’ll review the best candidate that is safe and easy to get.

What solvent will dissolve PLA filament?

Ethyl acetate, methylene chloride, propylene carbonate, acetone, and pyridine are the commonly used PLA solvents. The first three can be used to dissolve PLA supports or clean your printer, while the rest are mainly used to smooth or glue printed parts. The rate of dissolution mostly depends on the amount of solvent and exposure time.

There are many parameters to consider before choosing a solvent for PLA. Now let’s get into it and discuss our options, their applications, and safety issues.

PLA Solvents

1. Ethyl Acetate

This colorless liquid is commonly used in nail polish removers, glues, and industrial solvents. The low price, market availability, and safety of this material make it an ideal solvent for removing PLA supports or smoothing the print’s surface.

Speaking of safety, Ethyl acetate’s median lethal dose, LD50, is 5620 mg/kg for rats. It means that the material has low toxicity. However, there is still slightly there. 

Overexposure may irritate the nose, throat, and eyes. Severe cases can show drowsiness, weakness, and unconsciousness. According to an experiment from Toxicology by George D. Clayton, People exposed to a concentration of 400 ppm in 1.4mg/L ethyl acetate were affected by throat and nose irritation.

Thus it’s a good idea to use a safety mask and glasses while working with this solvent. You can also use it outdoors or in a well-ventilated area to inhale the least amount of ethyl acetate.

2. Propylene Carbonate

If you are looking for a safer solvent, you can choose propylene carbonate.

Clinical studies show that propylene carbonate doesn’t cause irritation and sensitization while combined with other chemicals for cosmetic preparations. However, moderate irritation may occur if it’s used undiluted.

Experiments attest that the laboratory mices fed propylene carbonate showed no significant toxic effects.

This material isn’t regulated as a volatile organic compound in the US because it doesn’t majorly contribute to smog formation.

3. Methylene Chloride

Another effective solvent is methylene chloride or dichloromethane. It’s a colorless organic liquid chemical with a sweet smell.

Compared with other solvents, this one can dissolve PLA faster. The actual amount of dichloromethane required varies depending on the situation. However, it’s always less than the required amount of ethyl acetate for that situation.

This video shows the process and output of smoothing PLA prints with methylene chloride.

Although dichloromethane is the least toxic of chlorohydrocarbons, it can still cause health issues because it is very volatile; thus, inhaling it can cause hazards. It can also go through the skin and be absorbed. Overexposure to dichloromethane and inhaling it can result in symptoms like headaches, fatigue, and numbness.

As you noticed, you should use dichloromethane with caution. If you want to use this solvent, you should:

• Wear protecting clothing, footwear, etc.
• Use PPE such as safety gloves and splash goggles.
• Do the process in a well-ventilated area.

Dichloromethane is highly effective against polylactic acid though it should be the last option due to its safety issues.

4. Pyridine

Pyridine is a water-miscible liquid with an unpleasant fish-like odor that is also flammable.

This material is accessible in different markets, and it’s synthesized over 20000 tonnes every year.

Pyridine is the material added to ethanol to make it unsuitable for making wine or direct drinking. It can be harmful if inhaled or absorbed through the skin.

The effects of overexposure to pyridine include headache and dizziness.

5. Acetone

As a solvent, acetone can work with many plastics though it’s incapable of dissolving pure PLA or polylactic acid.

But, there are some differences between pure PLA and the filaments made from PLA. Different companies use various compounds with different percentages to create their filaments.

Acetone can’t dissolve PLA though it can affect other components that are in the compound. Hence, you can use acetone to make slight changes in cases that complete dissolving isn’t necessary.

This solvent needs more time to modify the print. You may need to wait for hours to see observable results, while other solvents can affect the PLA filament in a matter of minutes.

You can find more details about smoothing PLA with acetone and see the results in the below video.

How to smooth PLA?

In most situations, you should sand the print before using any solvent.

The best method is to start from rough sandpapers and then use smoother ones as you proceed. For example, you can start your sanding in the most uneven areas with 300 grit, then go for other ones.

If the printed object has tight tolerances, you can start the sanding with smoother sandpapers and use an automobile primer.

The more patience and accuracy you put into your work, the better results you will get.

Using power tools to speed up the process isn’t a good idea because the generated heat can melt the part. However, using waterproof sandpaper can solve the problem. Wetting the print can absorb the generated heat.

After the sanding process, you can use one of the named solvents to dissolve PLA.

The best technique is to use a brush and slightly rub the solvent on the printed piece and wait until it evaporates. Note that adding too much solvent can cause stiffness or deformation.

Instead of dissolving PLA, you can use a polish compound to add a slick layer.

This approach is also simple. All you need is a mixture of epoxy resin and hardener. Then you can rub a thin layer of epoxy on the part and wait till it dries.

Hardened epoxy also has the ability to be sanded or milled.

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