Extruded Acrylic Sheet (PMMA) – Technical Material Specification for Canadian Fabrication & Machining
Comprehensive technical specification for extruded acrylic sheet (PMMA) covering standard Canadian stock sizes, tolerances, machinability parameters, common defects, and storage guidelines for fabrication, woodworking, and machining operations.
Material Overview & Common Uses
Extruded acrylic sheet (PMMA – polymethyl methacrylate) is a thermoplastic widely used in Canadian fabrication shops for its optical clarity, UV stability, and impact resistance compared to glass. Common applications include point-of-purchase displays, signage, light diffusers, machine guards, aquariums, and architectural glazing. Extruded acrylic offers tighter thickness tolerances than cast acrylic and is more economical for high-volume runs, but has lower chemical resistance and is more prone to stress cracking. Typical service temperature range is -40°C to 80°C. In Canadian climates, acrylic maintains dimensional stability across seasonal temperature swings, but care must be taken to avoid thermal shock during machining.
Core Technical Properties & Sizing
| Parameter | Value / Range | Notes |
|---|---|---|
| Standard Stock Sizes | 48" x 96" (1220 x 2440 mm) 60" x 96" (1525 x 2440 mm) | Custom cut-to-size available |
| Thickness Range | 0.060" (1.5 mm) to 1.000" (25.4 mm) | Common: 1/8", 1/4", 3/8", 1/2", 3/4", 1" |
| Thickness Tolerance (Extruded) | ±0.010" (≤0.250") ±0.015" (0.250"–0.500") ±0.020" (0.500"–1.000") | Tighter tolerances available (±0.005") |
| Flatness Tolerance | 1/8" per 48" length (Std) 1/16" per 48" length (Premium) | Per ASTM D4802 |
| Light Transmission | >92% (Clear) | Per ASTM D1003. Haze <1% |
| Tensile Strength | 10,000 psi (69 MPa) | Per ASTM D638 |
| Flexural Modulus | 450,000 psi (3.1 GPa) | Per ASTM D790 |
| Impact Strength (Izod) | 0.4 ft-lb/in (21 J/m) | Notched. Lower than cast acrylic |
| Vicat Softening Point | ~105°C (221°F) | |
| Continuous Service Temp | 80°C (176°F) | |
| CTE | 7.0 x 10^-5 in/in/°F | 12.6 x 10^-5 mm/mm/°C |
| Flammability | UL 94 HB | V-2 achievable with additives |
Machinability, Tooling & Feeds
| Process | Tooling / Specs | Recommended Parameters |
|---|---|---|
| Routing | Sharp carbide or PCD | 12,000–18,000 RPM, 100–200 IPM, DOC 0.020"–0.060" |
| Drilling | 118° point angle, peck cycle | 2,000–4,000 RPM, feed 0.005–0.010 IPR |
| Sawing | Carbide-tipped, 60–80 teeth | 3,000–4,000 RPM, feed 10–20 FPM |
| Laser Cutting (CO2) | 10.6 µm wavelength | 80–120 W for 1/4", speed 0.5–1.0 in/s |
| Coolant | Compressed air or mist coolant | Avoid oil-based coolants (causes crazing) |
| Edge Finishing | Flame polishing (propane/O2) | Or diamond buffing |
| Bonding | Acrylic cements (Weld-On 3, 4, 16) | Avoid acetone, MEK. 24-hr cure at 20°C |
Common Defects & Quality Control
| Defect | Description | Acceptable Limit (ASTM D4802) |
|---|---|---|
| Crazing | Fine surface cracks from solvent or thermal stress | Zero tolerance – reject |
| Chip-out | Edge chipping during machining | <0.001" deep |
| Surface Scratches | From handling or contact | <0.001" deep |
| Die Lines | Longitudinal streaks from extrusion | <0.002" deep |
| Thickness Variation | Out-of-tolerance gauge | ±0.020" max variation |
| Bowing / Warping | Uneven cooling or internal stress | Per flatness tolerance |
| Contamination / Bubbles | Embedded particles or gas pockets | <0.010" dia, max 5 per sq ft |
| Delamination | Separation of layers | Zero tolerance – reject |
Storage, Handling & Racking Guidelines
| Condition | Guideline |
|---|---|
| Orientation | Vertical in A-frame racks, 10–15° from vertical |
| Supports | Padded with foam or felt to prevent scratching |
| Max Stack Height | 20 sheets (1/8"), 10 sheets (1/4"), 5 sheets (≥1/2") |
| Masking | Keep protective film intact until fabrication |
| Temperature | 15–25°C (59–77°F) |
| Humidity | 40–60% RH |
| Light Exposure | Avoid direct sunlight and UV. Use UV-blocking film for long-term storage |
| Handling | Clean cotton gloves, two hands on edges, do not flex |
| Acclimation (Winter) | Allow 24 hours at shop temperature before machining |
| Proximity | Do not store near heat sources, solvents, or acids |