How Safe Are Solvents For Support Materials in FFF?

26. August 2021Dr. Andrei Neboian

Using support materials that need a solvent begs a critical question: How safe are these solvents? How Safe is VXL-EX?

Dissolvable support materials do a pretty good job at letting us produce any geometry with our FFF 3D printers. However, dissolving such materials is a task that deserves special attention.

We often see videos and image posts showing support structures melting away in a clean glass surrounded by a clean workplace. The process seems simple, clean, and perfect.

But the practical reality of dissolving supports looks much messier than these photos, videos, and advertisements. Without proper temperature control and agitation, PVA (or PVOH) will simply take too long to dissolve. Besides, bigger parts will need something larger than a glass.

Here is an image of our support removal workplace before we switched to professional support removal stations. Even though PVA supports dissolve in water, the workplace looks anything but a shiny ad for PVA.

Some of our older support removal stations (source: Xioneer).

So here comes the nagging question: If the support removal workplace can get so messy, how can we ensure that we are safe? This question is particularly relevant if you use support materials that require a solvent other than pure water.

Examples of such material-solvent combinations include HIPS + Limonene, VXL + VXL-EX, and eventually support materials requiring NaOH (caustic soda) to dissolve.

How safe are these material-solvent combinations?

Why Use Solvents At All?

Hold on. If we need to even think about safety when using solvents, why use them in the first place? I mean, can’t we just take PVA, PVOH, or any other water-soluble support material and be done with it? Yes, the workplace will be messy, but at least we can make sure that we stay safe.

But water-soluble support materials have some major drawbacks in 3D printing.

When it comes to temperature resistance, PVA, BVOH, etc., tend to degrade quickly inside the nozzle, leaving a clogged print-head now and then. This is the #1 reason people complain about these materials.

Once we mention reliability, all water-soluble filaments have another disadvantage. They rapidly absorb humidity from the surrounding air. This means that you need to store water-soluble materials under dry conditions or even dry them before use.

Another disadvantage of water-soluble supports is their incompatibility with a wide range of model materials. For example, PVA does not stick well to most model materials, but VXL bonds much better with PC, ABS, TPU, PETC, and other filaments. Besides, PVA has a too low melting point rendering it useless with high-temperature materials like PEEK. You must use VXL-130 to print PEEK.

Finally, water-soluble structures collapse into a gluey clump when placed in water. This means that such supports will dissolve slower. Moreover, water has a limited dissolving ability for polymers. So to really speed things up, adding a solvent can help you remove your supports more efficiently.

So let me summarize. Using supports that require a solvent besides plain water can provide major advantages over water-soluble supports: more reliable printing, better material compatibility, and faster dissolution.

HIPS and Limonene

HIPS is one of the oldest contestants to PVA in the open 3D printing community.

HIPS or High-Impact Polystyrene is a low-cost thermoplastic material often used to make mass goods and toys. It is similar to ABS but is softer and less durable. But the advantage of HIPS: it bonds well to other styrene-based materials such as ABS. This makes HIPS useful as support material.

To remove supports after printing, place your part in a bath with an organic solvent called Limonene. This solvent is made from orange peels. Oranges? It sounds pretty harmless, right?

But have you tried squirting an orange peel onto a candle? The tiny spray from the peel will burst in flames. The reason for this: Limonene inside the peel is a fierce flammable fluid. So using Limonene in your support removal workplace comes with risks of fire. Handle with care.

Finally, dissolving HIPS with Limonene may leave you with hazardous byproducts. Limonene can also irritate the skin. Therefore, most countries regulate the disposal of Limonene, making it unlawful to simply drain it into a sewer.

All this makes HIPS + Limonene a relatively unsafe combination in your 3D printing arsenal.

PLA and Caustic Soda (NaOH)

We tried this a few times in a lab. But we advise you not to try this at home.

We printed a part with ABS and used PLA as support material. To remove PLA, we placed the printed object into a highly concentrated caustic soda (NaOH) solution. The liquid disintegrated all of the PLA supports in a few hours, leaving only the ABS part behind.

While this method worked well in our experiments, we strongly advise against it for everyday use.

NaOH is an extremely dangerous chemical. It is colorless and odorless but highly corrosive, caustic, and therefore harmful. The level of harm depends upon the amount, duration, and activity. It can burn the eyes, skin, and inner membranes and cause temporary hair loss.

If you accidentally spill a concentrated acid on your skin, you will experience intense burning pain. In this case, you would run to the nearest sink and try to flush the chemical off your skin. But caustic soda (NaOH) is a deceptive chemical. Once it gets in contact with your skin, you will not have the same pain response. Unnoticed, the substance will eat through the flesh, causing severe poorly healing and potentially infected burns.

Some vendors still use NaOH to dissolve supports. So extreme caution is required to handle support removal using NaOH.

VXL and VXL-EX Washing Powder

VXL-EX Support Removal Agent (Source: Xioneer)

The newest – and probably the most reliable soluble support material on the market is VXL. It dissolves in a solution of water and VXL-EX – a specially developed washing powder for VXL.

Let me tell you the good news right away: VXL-EX is non-caustic and safe to use, unlike the solvents above. Mixed with water, it produces a mild-alkaline solution to dissolve supports 3D printed with the VXL filament.

When we asked the chemical engineer behind VXL-EX what was inside this powder, he didn’t hesitate to answer: “The solvent is similar to the washing powder we all use to clean our laundry.”

Some important factors determine the speed at which VXL-EX dissolves the VXL support material:

  • Temperature: Water Temperature determines how quickly the removal process is. For example, applying VXL EX within a heated bath will provide quicker results than utilizing lukewarm water. The recommended dissolving temperatures depend on the type of VXL and model material you use, ranging between 40°C to 90°C (100°F to 200°F).
  • Agitation: Stirring solvent around the 3D printed part and its supports will speed up the dissolving process. Think of dissolving a spoon of sugar in a cup of tea: the faster you stir, the faster the sugar dissolves.  
  • Amount of Supports: The rule of thumb for the amount of VXL EX is: 1:1. This means for every 100 g of VXL, you will need 100 g of VXL-EX to dissolve it. To save on material, we often use this trick: we clip away large chunks of easily accessible VXL supports before placing the part into a bath. Once larger support structures are cut off, VXL-EX will dissolve remaining supports much quicker.
  • Support Geometry: The more complex and intricate the geometry, the longer it takes to dissolve the supports. This makes sense, because the liquid flows slower in harder-to-reach areas and deep cavities. Here, increasing solvent agitation will help a lot.

You can learn 5 methods on how to effectively dissolve support structures in this article.

Unlike Limonene, VXL-EX creates a safer solvent due to its low corrosive features. But this does not mean that users should shun traditional safety post-processing practices when using any solvent. It is recommended that you still wear the appropriate protective equipment that protects the skin, eyes, and respiratory system when handling VXL-EX.

VXL-EX vs. Other Solvents

Limonene is flammable, known to react irritably with skin, release potent fumes, and cause irritation if it comes in contact with the eyes. VXL-EX would also cause irritation if you rub it into your eye, so always use protective gloves and eyeglasses to be on the safe side. But on the other hand, VXL-EX is not flammable and does not release toxic fumes.

More importantly, VXL-EX is non-caustic, making it much safer than caustic soda (NaOH).

So if you can handle a conventional laundry detergent, you will be able to handle VXL-EX to dissolve your VXL supports too.

The higher efficiency of the VXL + VXL-EX sets it further apart from other combinations. Limonene provides inconsistent results and can eat through and bleach out filament colors when used. But VXL-EX is a low corrosive removal powder that does not reduce the quality of the processed 3D print.

Where To Go From Here

Does a safe, reliable washing powder for removing support materials exist? The answer is yes.

VXL-EX provides 3D printing enthusiasts and professionals with a safe, reliable washing powder for removing support materials from VXL. The washing powder is mild and can be safely stored within tight containers for recurring post-processing activities, thereby saving cost.

Learn more about the washing powder VXL-EX, our support materials VXL, and our support removal stations.

Author:Dr. Andrei Neboian

Andrei is the founder and managing director of Xioneer Systems GmbH. He and his team have been developing 3D printing hardware for 10 years. Andrei is a writer, engineer, economist, and 3D printing aficionado.

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