How common plastics hold up against water-treatment chemicals, acids/bases, solvents, fuels and oils, curated to the materials and exposures most relevant to injection moulding and water metering applications.
Will Your Plastic Part Survive What It’s Actually Exposed To?
A part that looks fine on day one can swell, crack or dissolve after months in service. Not because it was moulded badly, because nobody checked how the material handles the chemicals it actually meets in the field.
This shows up constantly in water infrastructure. A meter housing or fitting sits in contact with treated water, ground moisture, cleaning agents and, periodically, concentrated disinfectant, for years, not days. The wrong material doesn’t fail in testing. It fails eighteen months into service, in the ground, where nobody’s watching.
How to Read a Chemical Resistance Rating
Resistance is usually rated on a simple scale:
- A – No attack. Possibly slight absorption, but negligible effect on mechanical properties.
- B – Slight attack. Some swelling and a small reduction in mechanical properties.
- C – Moderate attack. Appreciable absorption; the part will have a limited service life.
- D – Decomposes or dissolves. Not recommended for this exposure, full stop.
These ratings are for room temperature and the concentration stated. Hotter conditions or a stronger concentration than tested can push a material from “A” to “C” faster than you’d expect.
Chemical Resistance by Material
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Legend (verbatim source definitions): A = No attack, possibly slight absorption, negligible effect on mechanical properties. B = Slight attack by absorption, some swelling and small reduction in mechanical properties likely. C = Moderate attack, appreciable absorption, material will have limited life. D = Material will decompose or dissolve in a short time – not recommended. Ratings are at room temperature unless a concentration is noted in the chemical name; they describe general chemical compatibility only and are not a substitute for testing the actual part, chemical grade and concentration in service.
Disclaimer: Published in good faith, compiled and cross-checked against published industry and manufacturer chemical resistance data. Ratings can vary by concentration, temperature and material grade, for critical or regulatory applications, confirm compatibility with independent laboratory testing or the material manufacturer before final specification.
What This Looks Like in Practice
Take sodium hypochlorite – chlorine bleach, and the standard disinfectant in municipal water treatment. It’s one of the most common chemicals a water metering component will meet in service, and materials handle it very differently: some hold up cleanly at rating A, others degrade over time. That single choice, made once at the design stage, decides whether a housing lasts the meter’s service life or needs replacing early.
The same logic applies across the board – fuel and oil exposure for parts near vehicles or generators, acids and caustics in industrial and cleaning environments, solvents wherever degreasing happens. The right material for a chemical-heavy application usually isn’t the cheapest one or the one that’s easiest to mould. It’s the one rated A for whatever it’s actually going to sit in.
Common Questions
If a material is rated “A” for a chemical, is it safe at any concentration? No. Ratings are tied to a specific concentration and temperature. A material that resists a 10% acid solution at room temperature may not hold up against a concentrated version, or the same solution heated. Always match the rating to your actual operating conditions, not just the chemical name.
Two materials are both rated “A” – does it matter which one I pick? Often yes, for reasons beyond chemical resistance. Cost, mechanical strength, mouldability and shrinkage still differentiate them. Chemical resistance narrows the field; it’s rarely the only factor.
Why isn’t every chemical my part touches on the chart? This chart covers the chemicals most relevant to injection moulding and water metering applications specifically – it’s a working subset, not the full published reference. If you’re dealing with something specific to your process, tell us the chemical and concentration and we’ll check it against the full data.
For expert guidance on choosing the right plastic for your needs, contact Plastinternational today!
