Cast vs extruded acrylic
Both are PMMA — but how they're made changes everything about how they perform.
How cast acrylic is made
Cell-cast acrylic starts as liquid methyl methacrylate (MMA) monomer. The monomer is poured into precision molds — glass plates for sheet, or cylindrical molds for tubes and rods — and cured slowly at controlled temperatures. The polymerization happens in the mold, and the resulting material has a high molecular weight (typically over 1,000,000 g/mol).
This slow cure produces an acrylic with exceptional optical clarity, excellent chemical resistance, and minimal internal stress. US Cast has been using this process in Pittsgrove, NJ since 1954.
How extruded acrylic is made
Extruded acrylic uses pre-polymerized acrylic pellets that are melted and pushed through a die under pressure. The process is faster and cheaper — pellets in, continuous profile out. But the rapid heating and cooling introduces internal stresses, and the molecular weight is lower (typically 100,000–200,000 g/mol).
Why the difference matters
| Property | Cast | Extruded |
|---|---|---|
| Light transmission | 92% | 92% |
| Molecular weight | ~1,000,000+ | ~100,000–200,000 |
| Chemical resistance | Excellent | Moderate |
| Crazing resistance | High | Low — crazed by solvents |
| Machinability | Excellent — clean cuts | Tends to gum, melt |
| Thermoforming | Wider forming range | Narrower, more memory |
| Dimensional tolerance | Tighter (mold-set) | Looser (die variation) |
| Solvent bonding | Strong joints | Weaker — stress crazes |
| Price | Higher | Lower |
When to use cast acrylic
- Optical applications — sight gauges, flow visualization, laser windows — where clarity and freedom from distortion matter
- Chemical exposure — lab equipment, process piping, food/beverage contact — where solvent and chemical resistance are required
- Machined parts — precision-turned or milled components — where the material needs to cut cleanly without gumming
- Solvent-bonded assemblies — display cases, tanks, enclosures — where joints must be optically clear and structurally sound
- Outdoor or UV exposure — signage, architectural elements — where long-term clarity without yellowing is expected
When extruded is fine
If you're cutting sheet to shape with no machining, no solvent bonding, and no chemical exposure — extruded acrylic may be adequate at a lower cost. Common examples: simple signs, non-structural glazing, temporary displays.
But for tubes and rods — where the material is often turned on a lathe, bonded with solvent cement, or used in process equipment — cast is almost always the right choice.
What AAW sells
Every tube and rod at American Acrylic Works is cell-cast acrylic, direct from US Cast in Pittsgrove, NJ. We don't carry extruded material. Every order ships with a certificate of conformance to ASTM D5436, referencing the specific cast batch your material came from — see our credentials page.