PETG chemical resistance covers mild detergents and alcohols, and stops well short of strong alkali. A retail chain standardised on PETG for counter shields across 60 stores and issued a cleaning instruction that included an alkaline degreaser. The shields in twelve stores crazed within four months. The panels were within specification; the cleaning instruction was not.
PETG chemical resistance: the compatible list
- Dilute acids and most household detergents at working dilution
- Ethanol and isopropanol, short contact
- Aliphatic hydrocarbons such as kerosene and white spirit
- Silicone and mineral oils
- Water and steam cleaning below 60 degrees Celsius
That covers most retail, healthcare and food-display cleaning. It is also why PETG survives where acrylic would craze from a wipe-down.
The incompatible list, and why it matters
Strong alkalis, acetone and ketones, aromatic solvents, chlorinated solvents and concentrated degreasers all attack PETG. In most cases the chemistry alone produces slow surface dulling; the dramatic failure needs stress as well.
Stress cracking is the mechanism: a part with residual stress, usually from forming or from a tight fixing, fails along the stressed zone when the chemical reaches it. The crack runs from a corner or a hole, and the part separates without any impact.
Annealing and stress relief
Formed PETG carries orientation stress. Annealing at 65 degrees Celsius for one to four hours, depending on thickness, relieves most of it and cuts stress cracking dramatically.
That is a low-cost step and it is routinely skipped when parts are made in a hurry. The failures arrive three months later, in the field, on the customer’s counter.
Design details that avoid the problem
- Radius every internal corner, no sharp re-entrant angles
- Oversize holes and avoid tight fixings that preload the panel
- Keep formed parts out of direct contact with cleaning chemical reservoirs
- Specify the cleaner in writing, not just the panel
The cleaner specification is the one buyers forget. It costs nothing to write and prevents the most common field failure in display PETG.
Testing before a rollout
A simple immersion test answers the question for a specific chemical: cut three coupons, immerse one for 24 hours, one for a week, and keep one dry as a reference. Compare haze and flex both.
That is two weeks and three small pieces of sheet, against a rollout of sixty stores.
For food-contact duties the chemical question overlaps with compliance; the PETG food contact note covers the grade requirements, and the POS display guide covers the counter application where cleaning frequency is highest.
Send your cleaning chemical list to oversales@rpplexiglass.com; we will confirm compatibility in writing before you specify the panel.
Frequently Asked Questions
What chemicals attack PETG?
Strong alkalis, ketones such as acetone, aromatic solvents and some concentrated degreasers. They cause crazing or stress cracking rather than simple surface damage.
Is PETG resistant to alcohol?
Yes to short exposures with ethanol and isopropanol, which is why it is common in healthcare and retail cleaning regimes. Prolonged soaking is a different case.
Why did my PETG panel crack with no impact?
Almost always stress cracking: a stressed part, usually around a fixing or a formed corner, in contact with a chemical that would be harmless on an unstressed part.