Acrylic Grades — Cast, Extruded, Plexiglas, Acrylite, OP-3

Choosing the right acrylic grade starts with the manufacturing method — cast or extruded — then narrows by trade name, specialty formulation, and compliance requirement. This guide covers every major grade family: general-purpose cast and extruded, the Plexiglas and Acrylite brand lines, Optix continuous-cast, and OP-3 FDA-compliant sheet.

At a glance:

• Two base processes: cell-cast (highest quality) and extrusion (most economical)
• Cast grades: Plexiglas G, Acrylite GP — best for laser cutting and solvent bonding
• Extruded grades: Optix, generic extruded — tighter thickness tolerance, lower forming temp
• UV-filtering grades (Plexiglas UF, Acrylite OP-2) — required for museum and archival use
• OP-3 grade: FDA 21 CFR 177.1010 compliant for food-contact articles
• All grades available in sheet; cast also available in rod and tube

Cast vs. Extruded — The Foundational Choice

The single most important acrylic selection decision is between cast and extruded. Both are PMMA; the difference is in molecular weight, internal stress, thickness tolerance, and performance in specific fabrication processes.

Cell-Cast Acrylic

In cell casting, liquid monomer (MMA) is poured between two glass plates, polymerized under controlled temperature, and annealed. This produces a high-molecular-weight polymer (>1 million Daltons) with low internal stress and superior optical homogeneity.

Advantages of cast:

• Laser cuts with a polished, flame-quality edge — no post-processing
• Strong solvent-welded joints (high molecular weight → better polymer chain entanglement at the bond line)
• Lower internal stress → less warping or crazing over time
• Wider range of specialty formulations available (UV-filter, IR-blocking, color-shift)
• Available in larger sheet sizes (up to 8′ × 10′)

Limitations of cast:

• Thickness tolerance ±10% (a nominal 0.250″ sheet may measure 0.225″–0.275″)
• Higher cost than extruded
• Requires higher thermoforming temperatures (310–340°F)

Extruded Acrylic

Extrusion pushes acrylic pellets through a die at temperature, producing a continuous sheet. Molecular weight is lower (~350,000 Daltons) and internal stress is higher, but dimensional consistency is better.

Advantages of extruded:

• Tighter thickness tolerance ±5% (better for precision assemblies)
• Lower thermoforming temperature (290–320°F) and shorter cycle times
• Lower cost
• Dissolves more readily in solvents — useful for certain bonding applications

Limitations of extruded:

• Laser cut edge shows slight hazing on transparent pieces
• Solvent bond strength lower than cast
• Slightly lower continuous use temperature (180°F vs. 200°F)
• Fewer specialty formulations

Brand-by-Brand Grade Guide

Plexiglas (Röhm GmbH)

Plexiglas is the original trade name for PMMA, coined by Röhm in 1933. Today it refers to a broad line of cast and specialty acrylic grades:

• Plexiglas G — general-purpose cell-cast clear sheet. The benchmark for optical quality. Available clear and in a full color range.
• Plexiglas GS — equivalent to G, sold outside North America.
• Plexiglas UF-3 — UV-filtering cast sheet. Blocks >98% of UV radiation below 380 nm. Used in museum display cases and fine art framing.
• Plexiglas UF-4 — blocks UV and near-UV up to ~400 nm.
• Plexiglas MC (Mirror) — silver or gold mirror acrylic via vacuum metallizing.
• Plexiglas Satinice — frosted/matte cast acrylic for diffuse lighting and privacy panels.

Plexiglas G is available in 0.060″ through 4.000″ thicknesses and sheet sizes up to 8′ × 10′. It is the premium specification for laser cutting, solvent bonding, and optical applications.

Acrylite GP (Evonik)

Acrylite GP (formerly Cyro Acrylite GP) is a general-purpose cell-cast acrylic manufactured by Evonik. Properties are nearly identical to Plexiglas G. Acrylite GP is widely specified in the sign and display industry because of its consistent availability and color range.

Specialty grades in the Acrylite line:

• Acrylite OP-2 — UV-filtering, equivalent to Plexiglas UF-3
• Acrylite OP-3 — FDA 21 CFR 177.1010 compliant (see below)
• Acrylite FF — formulated for flame finishing; used in trophy and award fabrication

Acrylite GP is often the default specification in architectural drawings when a generic cast acrylic is required.

Optix (Plaskolite)

Optix is a continuous-cast acrylic manufactured by Plaskolite. It occupies the value tier between premium cell-cast (Plexiglas, Acrylite) and commodity extruded sheet. Optical quality is good but slightly below cell-cast, and the color range is narrower.

Optix is widely available through home improvement retailers and building supply channels in standard 0.093″ and 0.220″ thicknesses. It is suitable for general glazing, window replacement, and basic display applications where premium optical quality is not required.

For laser cutting or critical solvent bonding, specify Plexiglas G or Acrylite GP instead.

Generic Extruded Acrylic

Commodity extruded acrylic is produced by numerous manufacturers and sold under various distributor house brands. It is appropriate for:

• POP fixture fabrication (routed, not laser cut)
• Strip-heater bending
• Large-format thermoforming
• Any application where cost is the primary driver and optical perfection is not required

Do not use generic extruded for applications requiring strong solvent-welded joints or polished laser-cut edges.

OP-3 FDA-Grade Acrylic

Acrylite OP-3 (and equivalent grades from other manufacturers) is formulated to comply with FDA 21 CFR 177.1010, which governs acrylic and modified acrylic polymers intended for use in food-contact applications. OP-3 sheet is clear, cell-cast, and functionally similar to Acrylite GP with the addition of FDA-compliant formulation.

Key facts:

• Same machinability, optical quality, and thickness range as standard Acrylite GP
• Required when acrylic will directly contact food or beverage
• Commonly used in bakery display cases, deli shields, produce containers, salad bar rails
• Available in 0.093″ through 0.500″ in stock and cut-to-size

For the full FDA compliance discussion including food-display vs. food-contact distinction, see the FDA and food-grade acrylic guide.

Specialty Grades

Anti-Reflective (AR) and Hard Coat Acrylic

AR-coated cast acrylic reduces surface reflectance from ~4% per face to ~1% per face. Used in high-end retail displays and fine art framing. A separate hard coat (silicon-based) reduces surface scratch susceptibility for high-traffic applications. Neither coating is compatible with standard solvent bonding — use acrylic-compatible structural adhesive.

Impact-Modified Acrylic

Rubber-toughened PMMA grades offer improved impact resistance (1–2 ft-lb/in notched Izod vs. 0.3–0.5 for standard) with some sacrifice in optical clarity. For very high impact requirements, polycarbonate remains the correct choice.

Colored and Tinted Acrylic

Transparent tints (bronze, smoke, gray, blue, red, amber) serve glazing and display lighting applications. Opaque colors (white, black) are used in sign letters and display bases. Specify weather-grade colors for outdoor use — standard interior formulations fade in direct sun.

Grade Selection Quick Reference

Ready to order? View stock grades, thicknesses, and colors on the acrylic line card.

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