Thermoplastic
Acrylic (PMMA)
The clearest common plastic, and the most scratch resistant.
Published values for unfilled grades at 23 °C unless stated. Confirm against the supplier datasheet for the grade you specify.
What it is
Acrylic transmits 92 % of visible light, more than glass, and it holds that clarity outdoors for decades where polycarbonate yellows. Its surface is hard enough to resist the fine scratching that dulls PC lenses in service.
It is brittle. Notched impact strength is around a twentieth of polycarbonate, and it fails by cracking with no yield warning. That single property decides most acrylic-versus-polycarbonate arguments.
Where it is used
- Light guides, lenses, and display windows
- Point-of-sale and retail display components
- Instrument faces and fascia panels
- Machined optical prototypes
- Outdoor signage and glazing
Processing notes
Dry 2–4 hours at 80 °C. Moisture shows immediately as bubbles in a clear part.
Melt 210–250 °C, mold 60–90 °C. Slow injection and high hold pressure give the best optical result.
Machined acrylic chips and cracks at the tool exit. Sharp tools, high speed, low feed, and climb milling on the final pass.
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Design notes
Radius everything. A sharp internal corner in acrylic is a crack waiting for its first shock load.
Avoid press fits, self-tapping screws, and any assembly that leaves the part under sustained tension.
Flame or vapour polishing recovers optical clarity on machined edges; sanding alone will not.
Grades and variants
- Cast sheet, best optical quality and thickness tolerance, machined only
- Extruded sheet, cheaper, easier to thermoform and laser cut
- Impact modified, recovers some toughness at the cost of clarity
- UV transmitting or UV blocking grades
- Optical molding grade with tight refractive index control
Alternatives
If Acrylic (PMMA) is not the right answer
Specifying this material?
Send your CAD and target volumes. We come back with a price, a lead time, and any material or design notes that would reduce either.