Acetone can be used to smooth ABS prints. What safety precautions should be taken during its use?
Acetone can be used to smooth ABS prints. What safety precautions should be taken during its use?
There are a few main safety precautions you should consider.
Acetone is toxic, as I mentioned before, but it is not highly toxic. Exposure via the eyes and nose/mouth is the main risk. Skin effects may occur (e.g. mild irritation), but they are minor and generally arise only after long-term exposure (hence the recommendation of gloves in some cases).
Acetone exposure is only a serious problem when a person is repeatedly exposed to levels greater than 1,000 ppm (severe effects only arise at much higher levels). It seems unlikely, given a proper ventilation system, that this will be an issue
In addition to all this, basic safety precautions such as wearing a ventilator mask and goggles should definitely be taken. When working with any such chemicals with the potential for bodily harm, these should absolutely be used.
Contrary to what the other answers suggest, the risk of fire is not that great. An acetone "explosion" is even more unlikely, since you need a ratio of 2.5%-12.8% acetone vapor to air for that: too much acetone (as would be the case inside of your smoothing vessel) and nothing happens, too little (as would be the case inside of a badly ventilated room) and nothing happens either.
Note that even if you were working in a completely non-ventilated, ridiculously small 1m^3 room you'd still need to evaporate over half a liter of (liquid) acetone to reach that bare minimum 2.5%. In any case, well before you got into the "danger zone" the air would become unbreathable.
So, then what should you be mindful of when using acetone?
It can give you a headache. Avoid breathing the fumes and ensure adequate ventilation.
You may opt to use gloves, as skin contact should be avoided (acetone can irritate the skin and possibly be absorbed through the skin). However, limited skin contact isn't a big deal: acetone is an ingredient in some nail polish removers.
Acetone is heavier than air, so if you use a sufficiently high container fewer fumes will escape.
If somehow a fire does start, it will likely be limited to your container. Having a lid handy allows you to starve the fire of oxygen, harmlessly putting it out.
All in all, smoothing using acetone is not very dangerous. Acetone isn't suspected to be carcinogenic, though it isn't something you should be careless around either. The risk of starting a fire is small. On the other hand, solvents like MEK (used for smoothing PLA) aren't as nice by far, and should only be handled with a respirator.
You should also avoid skin contact; repeated exposure may cause skin dryness or cracking, but this never happens me if I wash my hand after using acetone.
Please remember that you handle acetone at your own risk! By using this advice you agree to hold me harmless and not sue me as a result of using these instructions/advice. Remember that I am not a professional chemist or a lawyer (this isn't professional or legal advice)!
I encourage you to research safety precautions and risks on your own to build a personal body of knowledge. The most effective safety precaution available to you is knowledge; the brain is the most important piece of safety equipment! This listing of advice for acetone handling is generated from the highlights of a Material Safety Data Sheet (MSDS) for acetone. After reading this advice you should read an MSDS for acetone directly. It would actually be an excellent idea to find and read the MSDS for all the chemicals you use during 3D printing.
Wear safety clothing! Acetone requires that you wear protective gloves, protective eyewear, and a respirator (to protect your airway). It is also highly recommended to wear protective (ideally also chemically resistant) clothing (like a smock or an apron). These safety clothes are recommended because acetone is a toxic substance which can absorb through the skin and walls of the lungs directly. Make sure to verify the gloves are made of a substance which blocks acetone absorption, also, verify that your respirator is rated to protect against acetone (many respirators are not capable of blocking acetone due to it's volatility).
Possess, prepare and understand how to use an eyewash station, a fire blanket, a fire extinguisher (rated for chemical fires), a chemical shower/dousing system and other standard laboratory safety equipment. Posting warning signs along the entrances and exits to the work area about working with a volatile, flammable and explosive gas is also recommended.
Keep an inert absorption media readily available to cleanup spills should you accidentally fail to avoid a spill. Diatomaceous earth, silica/sand and activated charcoal are all potential absorption media. Should you have a large spill or not possess absorption media (which should not happen - always verify safety equipment is present and working before handling chemicals!) then you may also dilute the spill with water and mop up the dilute solution of acetone. No matter which method you use to cleanup a spill remember to dispose of the contaminated cleanup materials according to the requirements/laws of your local area. Do not lazily dispose of the acetone down the drain without doing research on the correct disposal methods!
Control Your Environment
Ensure proper ventilation of your workspace (ventilation is required in addition to your respirator due to explosion/fire risk). If the atmospheric concentration of acetone becomes too high the risk for fires and explosions quickly becomes unacceptable (the risk is never going to be zero working with acetone unfortunately, but minimizing it is very important). Working outside is the perfect way to insure the ventilation is adequate, although that presents it's own problems and considerations. Alternatives include using a fume hood, or even something as simple as a fan blowing air through an open window.
Eliminate any and all sources of flame or spark for a considerable area around all sources of acetone (10-15 meters minimum). Take special precautions to prevent being unknowingly contaminated with acetone (which could then be accidentally transported from the work area to a flame source using you as a carrier). Personal contamination can lead to injury if you attempt to smoke during a break or at anytime before verifying you are not contaminated. It is important to provide an ignition-free environment that extends quite far away from the immediate vicinity of the acetone because acetone can ignite a vapor trail of acetone and allow the flame to travel distances via flashing over the vapor trail. Physical isolation is the ideal solution to this dangerous problem. A policy of always closing the door to the acetone work area is an example of physical separation which would hopefully prevent this vapor trail flash-over.
Avoid acetone spills. Acetone is an excellent solvent which could easily eat away the paint on your wall or destroy the finish of your table. Spills also necessitate following special precautions for cleanup and disposal, which have already been provided earlier within this list.
Do not under any condition mix your acetone with chemicals without an extensive analysis and understanding of the products and the risks associated with the reaction. The following list of chemicals will create an explosive compound/mixture when reacted with acetone, so do not allow them to come into contact with acetone: hydrogen peroxide, acetic acid, nitric acid, nitric acid + sulfuric acid, chromic anydride, chromyl chloride, nitrosyl chloride, hexachloromelamine, nitrosyl perchlorate, nitryl perchlorate, permonosulfuric acid, thiodiglycol + hydrogen peroxide, potassium ter-butoxide, sulfur dichloride, 1-methyl-1,3-butadiene, bromoform, carbon, air, chloroform, thitriazylperchlorate.
Should you accidentally ignite some acetone, you must take additional precautions while evacuating or while attempting to extinguish the fire. Acetone is a hydrocarbon and the reaction of burning it produces products which include carbon monoxide (CO) and carbon dioxide (CO2). Essentially, humans are incapable of detecting these gases with their senses (detectors exist to measure concentration). However, these symptoms of carbon monoxide and carbon dioxide can help alert you to the fact they are present: shortness of breath, blackness along the edges of your vision, confusion, headache, unconsciousness, coma, and finally, death. Carbon monoxide is far more dangerous than carbon dioxide because often the first symptom is unconsciousness, which prevents you from evacuating, leading to death. The dangerous of gas inhalation are substantial enough that as soon as a fire becomes medium-sized you should seriously consider evacuating the area rather than staying to extinguish the fire. It is better to lose property to the fire than to die (if you die I would guess that your property is destroyed anyway!).
Acetone is a confirmed developmental toxin for females and a suspected developmental toxin for males as well. The risk of breast milk contamination is unknown, but it is a suspected toxic contaminant. Mutagenic and tetragenic effects are not known. The result of this toxicity is that pregnant or breastfeeding women should not handle or be around acetone (due to vapors) even for short periods of time.
The risk of cancer and the carcinogenic properties for acetone are not well-defined, with some declining to classify acetone as a carcinogen and others classifying it as being carcinogenic. California, for instance, has required that acetone bear a proposition 65 warning about cancer risk.
Acetone is definitely a toxic substance, but it is not highly toxic and accidental ingestion or absorption is essentially incapable of causing severe symptoms. Small exposures to acetone (like the exposure levels likely encountered during 3D printing) are more-or-less not very harmful. However, if you do get a problematic exposure to acetone, contact a poison control center.
The LD50 ("lethal dose 50%", dose where half of subjects die) in rats is 5800 mg/kg, making the predictable (humans are often similar to rats in regards to toxicity) LD50 for an adult human similarly high. With such a high lethal dose, the predicted toxicity of acetone likely causes chronic sub-lethal damage instead of causing an acute and lethal response. If we assume an average adult human (62 kg) shares the LD50 of a rat- that human would need to consume 392 cc of acetone to reach the LD50. 392 cc is nearly equivalent to 4/10 L- meaning that there is essentially no chance the small consumption of acetone caused by working with it could poison an adult human (if our assumptions are correct).
Potential effects of inhalation, ingestion or skin absorption of acetone: dry skin, nausea, vomiting, skin irritation, eye irritation, burning sensation, redness, tearing, inflammation, corneal injury, depression, fatigue, excitement, stupor, insomnia, hypersomnia, ataxia, tremors, dizziness, drowsiness, confusion, headache, muscle weakness, loss of motor coordination, speech abnormalities, narcotic effects, coma, kidney damage, liver damage, brain damage, and death.
Repeated exposure to acetone can lead to the skin becoming sensitised, which means that in the future it will become overly irritated at the slightest contact.
On a more mundane note, it is an excellent degreaser and dries your skin something rotten. And then your fingertips can split and take days or weeks to close up, hurting in the meantime.
You can smooth a print with acetone using different approaches which require different precautions. In general, you should have ventilated area and use gloves (or wash your hands after the procedure).
Using the print in acetone for several seconds or you can apply acetone with a brush. There is a low possibility of fire. See this video, (4) MakerBot Replicator - Model Finishing Tricks - Acetone Wash.
This process takes several hours and gives you best control of the process. Because no external heat is used there is low chance of fire. See this video, Cold Acetone Vapor Finishing for 3D Printing.
This approach takes minutes to smooth the print and there is high chance of ignition. I would never use it inside a building. See this video, Make your 3D Printed parts look professional with Acetone and a Rice cooker! - 2014.