Short answer
Acrylic (PMMA) generally tolerates water-based liquids, mild detergents, many oils and dilute acids and alkalis, but it is attacked by many organic solvents such as acetone, ketones, esters and aromatic or chlorinated hydrocarbons. Even chemicals that do not dissolve it can cause fine cracks (crazing) when the part is under stress. Because results depend on concentration, temperature, exposure time and stress, treat any list as guidance and test on a scrap piece.
What acrylic tolerates
Compatibility charts from suppliers generally rate acrylic as resistant to:
- Water and mild soapy water.
- Dilute inorganic acids and many aqueous salt solutions.
- Dilute alkalis in many cases.
- Many mineral and vegetable oils and fats at room temperature.
The key phrase is “at room temperature and low stress.” Charts usually give ratings for specific concentrations and temperatures, so check the one for your chemical.
What attacks acrylic
Commonly listed as not recommended:
- Ketones such as acetone.
- Esters.
- Aromatic hydrocarbons such as benzene, toluene and xylene.
- Chlorinated solvents such as chloroform and methylene chloride.
- Strong or concentrated alcohols, which can cause crazing, particularly on stressed parts.
- Ammonia-based cleaners, which many sheet suppliers advise against.
- Concentrated strong acids and oxidizers.
Many fabricators intentionally use certain solvents for joining acrylic, since solvent cement works by softening the surfaces so they fuse. That same property is why you want to keep solvents away from finished parts.
Stress cracking and crazing
Crazing looks like a network of tiny hairline cracks that makes clear acrylic look frosted or cracked. It is caused by a combination of internal or applied stress and exposure to a chemical that would not necessarily harm unstressed plastic.
Stress can come from:
- Laser cutting or engraving, which leaves heat-affected edges (see acrylic laser cutting settings for ways to reduce edge stress).
- Bending or thermoforming.
- Tight fasteners or press fits.
- Machining that heats the material.
To reduce risk, avoid overtightening screws, use oversized holes with washers, and consider annealing parts according to the supplier’s instructions. Heat limits are covered in acrylic heat resistance.
Cleaning acrylic safely
A safe approach for most acrylic:
- Rinse loose dust with clean water to avoid scratching.
- Wash with mild soap or a cleaner made for plastics, using a soft microfiber cloth.
- Rinse and blot dry.
- Use a plastic polish for light scratches, following the product instructions.
Avoid glass cleaners containing ammonia, acetone-based nail polish remover, and abrasive pads. If you are unsure about a cleaner, try it on an offcut first.
Acetone and which plastics tolerate it
Acrylic is not compatible with acetone, which can soften, cloud or dissolve it. Plastics often described as having better resistance to acetone include polyethylene and polypropylene, PTFE and some other fluoropolymers, and PEEK, but ratings vary by contact time and temperature. By contrast, ABS, polystyrene, polycarbonate and PVC are generally affected by acetone. Always consult a chart for your specific plastic and exposure.
What is Lucite?
Lucite is a brand name associated with acrylic resin and products. Chemically, it is a form of PMMA, so the same chemical cautions apply. The name is sometimes used loosely for clear acrylic, much like Plexiglas.
Downsides of acrylic
- Brittle compared with polycarbonate, so it can crack under impact (see impact strength of plastics compared).
- Scratches more easily than glass.
- Limited heat tolerance.
- Sensitive to solvents and prone to crazing.
- Combustible.
- Can build up static and attract dust.
Does acrylic resist heat?
Only up to a point. It softens near 100 C and is generally used well below that. See acrylic heat resistance for the details.
Testing before you commit
When a part will meet unfamiliar chemicals:
- Check the manufacturer’s compatibility chart for the exact product.
- Test on an offcut treated the same way as the finished part, including laser cutting or bending.
- Observe for hours or days, since crazing can appear later.
- When in doubt, choose a more chemically resistant material.