When you specify acrylic sheets for a fabrication project, one of the first decisions is whether to use cast acrylic (cast PMMA) or extruded acrylic (XT). They look similar, but they perform very differently in bending, machining, gluing, and outdoor exposure. Getting this wrong can lead to cracked panels, failed bonds, or delayed shipments — so it pays to understand the difference before you place your PO.
What Is Cast Acrylic?
Cast acrylic is polymerized in a cell (two glass plates clamped together) using a methyl methacrylate monomer. The process produces a sheet with high molecular weight, excellent optical clarity, and tight thickness tolerance. It is the premium grade used for aquariums, optical applications, laser engraving, and outdoor signage.
What Is Extruded Acrylic?
Extruded acrylic is produced by pushing molten PMMA pellets through a flat die. It is faster and cheaper to make, but the molecular weight is lower and the thickness tolerance is wider (typically ±10% vs ±10% on cast, but XT runs to tighter long-length tolerances). Extruded sheets are ideal for simple glazing, lighting diffusers, and indoor display applications where cost matters more than premium optical performance.
Side-by-Side Comparison
- Optical clarity: Cast is superior — lower haze, better light transmission (up to 92%).
- Impact strength: Cast is more impact-resistant and less brittle.
- Bending / thermoforming: Cast bends more cleanly and is less likely to craze.
- Machining: Cast machines beautifully (CNC, routing, polishing); XT can chip or melt at high feed speeds.
- Gluing / bonding: Cast bonds more reliably with solvent cement (Weld-On 4, dichloromethane).
- Thickness range: Cast available from 1.5 mm up to 300+ mm; XT typically 1–12 mm.
- Outdoor UV resistance: Cast holds color and clarity longer outdoors.
- Cost: XT is roughly 15–30% cheaper than cast for the same gauge.
When to Choose Cast Acrylic
Specify cast PMMA when:
- The application is a thick panel (12 mm and up) such as an aquarium window or ballistic interlayer.
- The part will be laser engraved, diamond polished, or flame polished.
- The panel lives outdoors for 10+ years (sound barriers, canopy glazing).
- You need tight color consistency across a multi-piece order (sign faces, light boxes).
When Extruded Acrylic Is Good Enough
Choose extruded XT when:
- Indoor display, POP signage, or furniture parts where cost is the primary driver.
- Thin gauges (1–3 mm) for light diffusers, guard covers, or protective screens.
- Long, continuous sheets for large-area glazing where tight thickness tolerance is less critical.
A Note on Polycarbonate
If impact resistance is the top priority, neither acrylic may be the right choice — solid polycarbonate (PC) is 250 times more impact-resistant than glass and 30 times stronger than acrylic of the same gauge. Use PC for machine guards, riot shields, and bullet-resistant glazing. Acrylic wins on stiffness, scratch resistance, and optical clarity for non-impact applications.
How RP River People Helps
At our Anqing factory we run both casting and extrusion lines. We can supply cast PMMA from 1.5–300 mm and extruded XT in standard and custom widths, cut to your drawing. Send us the thickness, size, color, and application — we will recommend the right grade and quote within one working day. Contact our sales team for a quote today.