Material guide Scratch and impact
Acrylic and polycarbonate fail differently. Acrylic is the harder face: it marks less readily, and it chips or cracks when it is struck. Polycarbonate takes the blow better, and an uncoated face scratches sooner. Pick the failure you can live with. A brochure “times stronger” figure is not that choice.
The short answer
Decision rule. If the part will be looked at and wiped, and a crack is unlikely, start with acrylic. If the part may be struck, and a scratch is acceptable or will be coated, start with polycarbonate. If you need both a hard face and high impact, you are specifying a coated sheet or accepting a compromise — say which.
Two different failures
Scratch and impact are not one “strength” number.
A scratch is a surface event. Dust, a ring, a dry wipe, or a stacked part marks the face. On a clear display the mark is visible because the face is the product. Acrylic’s harder surface is why display shops stay with it for cubes and trays. Uncoated polycarbonate marks sooner under the same wipe.
Impact is a through-thickness event. A dropped SKU, a cart, a public elbow. Acrylic can chip at a corner or crack from a point load. Polycarbonate more often flexes and stays in one piece. That is why guards and covers go to polycarbonate even though the face is softer.
A part can be good at one and ordinary at the other. Asking which plastic is “stronger” skips the question of which failure the job cannot accept.
Scratch versus impact
Directional only. Grade, thickness, a coating, and the actual blow move every cell. This is not a lab table.
| Acrylic (PMMA) | Polycarbonate (PC) | |
|---|---|---|
| Uncoated face | Harder; scratches show, but less readily | Softer; fine scratches appear sooner |
| Under a point impact | Chip or crack is the common failure | More often flexes; stays intact more often |
| Corner and edge | Polished edges look good and chip if struck | Edge practice differs; impact is more forgiving |
| After a hard coat | Less often needed for scratch | Can close the scratch gap; coat is its own spec |
| What the buyer notices first | A haze of wipe marks, or a chipped corner | Fine scratches, unless the part was hit |
ISO 7823 covers PMMA sheet. ISO 11963 covers polycarbonate sheet. Neither standard is a scratch ranking or an impact ranking for your part. A pencil-hardness or a falling-weight number belongs to a named grade and a named method. Without both, leave it off the page.
What a hard coat changes
A hard coat is how polycarbonate is made presentable in a high-touch clear application. It can make the face closer to acrylic on scratch, and it can complicate a later polish, a bond, or a field repair. Write the coat on the drawing. “Polycarbonate” alone does not include it.
Coated acrylic exists too. On a normal display it is often unnecessary, and it is another process step. Specify it only if the wipe path is severe enough to justify it.
Which failure to accept
Cosmetic cube, jewelry tray
Accept a chip risk you will manage with thickness and pack. Do not accept an easily scratched face. Acrylic.
Guard, cover, public barrier
Accept scratches, or specify a coat. Do not accept a crack as the normal failure. Polycarbonate.
Counter well that gets dropped into
Name the drop. A brand face that is also a drop target is the compromise case: thicker acrylic, or coated PC, said out loud.
Staff-only back panel
Scratch matters less. Impact may still matter if carts hit it. Choose on the blow, not on the look.
Acrylic constructions in the first card are the usual retail set: boxes, trays, and display stands.
Cleaning is part of the scratch
Most display scratches are not impact. They are grit moved by a wipe. A dry cloth on a dusty acrylic face hazes it. The same wipe on uncoated polycarbonate hazes it faster. Alcohol can also craze a stressed acrylic face — a different defect from a scratch, and still a reason to name the cleaner.
If store staff will wipe the part daily, the material choice and the cleaner are one brief. “Scratch-resistant” without a cleaning note is incomplete.
What to write on the RFQ
- PMMA or PC.
- Which failure is unacceptable: scratch on the camera face, or a crack from a blow.
- Whether a hard coat is required — and on which faces.
- Thickness, because a thin acrylic cracks sooner and a thin PC flexes more.
- The cleaner, if the face is wiped on a schedule.
Sanait fabricates acrylic displays. A brief whose unacceptable failure is impact should say polycarbonate in the first email, so the plant can confirm scope or decline. Intake is on the FAQ. What the plant builds is on the about page.
FAQ
Which scratches less, acrylic or polycarbonate?
Uncoated acrylic, in ordinary display grades. A hard coat on polycarbonate can close or reverse that. Specify the surface.
Which is better for impact?
Polycarbonate, as a direction. Acrylic is more likely to chip or crack. The size of the gap depends on grade, thickness, and the blow — do not publish a single multiple.
Can I have both?
Only as a compromise: coated polycarbonate, or thicker acrylic with the crack risk accepted. Say which failure you are buying down.
Does thicker acrylic fix impact?
It helps a given part survive a given load. It does not turn acrylic into polycarbonate. Thickness is not a material change.
Why did my acrylic display haze in the store?
Usually grit and a dry or rough wipe, sometimes a cleaner that crazed a stressed face. The polymer name did not cause it alone.
Is “scratch-resistant polycarbonate” just polycarbonate?
No. It usually means a coated sheet. The coat, the faces it covers, and whether you may polish or bond later all belong on the drawing.
Sources
The trade-off above is directional. The standards identify the sheets. They do not rank scratch or impact for an unnamed grade.
- ISO 7823-1:2003, Plastics — Poly(methyl methacrylate) sheets — Part 1: Cast sheets. iso.org
- ISO 7823-2:2003, Plastics — Poly(methyl methacrylate) sheets — Part 2: Extruded sheets. iso.org
- ISO 11963:2019, Plastics — Polycarbonate sheets — Types, dimensions and characteristics. iso.org
- “Poly(methyl methacrylate).” Wikipedia. en.wikipedia.org
- “Polycarbonate.” Wikipedia. en.wikipedia.org
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