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PMMA · Acrylic · Plexiglas

92% transparent.
Polishes to optical grade.

Better optical clarity than polycarbonate, harder surface, cheaper material. Acrylic is the default for transparent enclosures, light guides, displays, and optical fluidic devices. Cast or extruded, machined or polished.

01 · Grades & variants

PMMA grades.

The main distinction is cast vs extruded, which affects machinability, optical quality, and price. Specialty grades for impact, UV, and optical applications.

Cast PMMA

Premium · optical grade

Plexiglas GS / Acrylite GP. Cast-polymerized between glass plates. Superior optical quality, excellent polish, standard for display and optics. Slightly higher cost than extruded.

Extruded PMMA

Economical · general

Plexiglas MC / Acrylite FF. Extruded from molten polymer. Faster to produce, lower cost, slightly less optical quality. Fine for enclosures and general transparent parts.

Impact-modified PMMA

Higher impact · Plexiglas DR

Rubber-toughened acrylic with 5–10× the impact strength of standard PMMA. Less transparent (~88%). Bathroom fixtures, vehicle windows, impact-prone applications.

UV-stabilized PMMA

Outdoor · 30+ year life

UV absorber package gives 30+ year outdoor life without yellowing. Standard acrylic yellows modestly; UV grade is indistinguishable new vs after 30 years.

Optical PMMA

Low-birefringence

Low internal stress, low birefringence for polarization-sensitive applications. Camera lenses, display covers, optical sensor windows.

Medical PMMA

USP Class VI

Biocompatible for short-term skin contact and fluid contact. Dental aligners, IVD device housings, microfluidic chips, ophthalmic lens trials.

02 · Why this material

Why acrylic over other transparent plastics.

Acrylic dominates transparent plastic applications where impact isn't the driver. It beats PC on clarity, scratch resistance, and cost.

Higher light transmission

92% vs 89% for polycarbonate. Matches or exceeds glass (90–92%). Critical for optical devices, lightguides, and premium display applications.

Scratch resistance

Surface hardness 2H–3H pencil (vs PC 2H). Does not mar as easily under everyday handling. For scratch-critical, specify hardcoated PMMA (5H).

Lower cost

Approximately 50% of polycarbonate cost per kg. For non-impact transparent applications, acrylic is the economic choice.

Polishes to optical finish

Flame, vapor, or diamond polishing achieves Ra 0.05 µm mirror finish. Adequate for many optical applications without coating.

03 · Applications

PMMA applications.

Display covers

Trade show displays, POS display cases, museum exhibits

Lightguides & LGPs

Edge-lit LED panels, smartphone backlights, automotive light guides

Microfluidic devices

Lab-on-chip, PCR chips, organ-on-chip research platforms

Signage & POP

Retail signage, dimensional lettering, backlit signs

Optical windows

Scanner glass, instrument viewports, laboratory glazing

Architectural glazing

Skylights, canopies, pool enclosures (UV-stabilized)

Aquariums

Large-format tanks — acrylic replaces glass for strength and clarity

Automotive lenses

Instrument cluster covers, tail lamp components, interior lighting

Medical devices

Infusion chambers, microfluidic chips, IVD reagent cells

04 · Finishing

PMMA finishing.

As-machined

Typical Ra 1.6 µm frosted finish. Tool marks visible — usually requires secondary polishing for optical use.

Flame polished

Hydrogen or oxygen-propane flame polishes to near-transparent. Fast but less consistent than mechanical.

Diamond polished

Diamond wheel polish to Ra 0.05 µm optical finish. Premium finish for optical components.

Vapor polished

Methylene chloride vapor smooths surface — faster than mechanical, creates slight crazing risk.

Hardcoated

Silica hardcoat raises surface hardness to 5H pencil. For touch-screen covers, scratch-critical applications.

Anti-reflection

Optical AR coating for display covers, reduces surface glare and reflection.

Tinted

Transparent tinted in bronze, grey, green, blue. For privacy glazing, sunglasses lens prototypes.

Laser cut edges

Laser cutting produces polished transparent edge — no secondary polish needed on cut edges.

FAQ

PMMA / Acrylic questions.

Choose PMMA when: optical clarity is priority, cost matters, surface scratch resistance is needed, part is not impact-critical. Choose PC when: impact resistance is required, high-temperature service needed, part could be struck or dropped. Rule of thumb: PMMA for "display this," PC for "protect this." PMMA is roughly half the cost of PC per kilogram.
Standard acrylic is brittle — impact strength 15 J/m notched Izod (vs polycarbonate 850 J/m). Sharp impacts or over-tightened fasteners can crack acrylic. For applications where impact matters, specify impact-modified PMMA (10× standard impact) or switch to polycarbonate. Avoid sharp internal corners (use fillets R ≥ 1 mm) and avoid tight fastener fits (use oversized holes with shoulder washers).
Yes — acrylic thermoforms well at 160–180 °C. CNC machined parts can be line-heated and bent to create 3D shapes. For complex curves, vacuum forming or press forming from flat sheet. Acrylic holds its formed shape indefinitely if fully cooled below Tg (105 °C).
FDA-compliant PMMA grades exist for food contact per 21 CFR 177.1010. Standard cast or extruded acrylic is usually not food-safe by default. For food applications (cake displays, food preparation tools, beverage dispensers), specify FDA-grade acrylic explicitly. USP Class VI grades for medical fluid contact.
Standard acrylic yellows only slightly over decades — far less than polycarbonate or ABS. UV-stabilized PMMA (with UV absorber package) is rated for 30+ years outdoor without visible yellowing. For outdoor signage, skylights, and architectural glazing, specify UV-stabilized grade.
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