PETG (Polyethylene Terephthalate Glycol) Sheet Technical Material Specification
Comprehensive technical specification for PETG sheet, covering properties, sizing, machinability, defects, and handling for Canadian fabrication and machining operations.
Material Overview & Common Uses
PETG (Polyethylene Terephthalate Glycol) is an amorphous thermoplastic known for its excellent impact resistance, clarity, and ease of fabrication. It bridges the gap between acrylic and polycarbonate, offering superior chemical resistance and formability without the brittleness of acrylic or the high cost of polycarbonate. In Canadian shops, PETG is widely used for point-of-purchase displays, machine guards, medical device housings, food-contact containers (when FDA-compliant), and thermoformed parts. Its low moisture absorption and good UV stability make it suitable for both indoor and outdoor applications, though prolonged outdoor exposure may require UV-stabilized grades.
Core Technical Properties & Sizing
| Property | Value / Rating | Standard / Notes |
|---|---|---|
| Density | 1.27 g/cm³ | Typical |
| Tensile Strength | 50–55 MPa (yield), 60–70 MPa (break) | ASTM D638 |
| Flexural Modulus | 2.1–2.4 GPa | ASTM D790 |
| Impact Strength (Izod notched) | 80–100 J/m | ASTM D256 |
| Heat Deflection Temp (HDT) @ 0.455 MPa | 70°C (158°F) | ASTM D648 |
| Continuous Service Temperature | -40°C to 65°C | Typical |
| Light Transmission (clear grade) | 88–90% | ASTM D1003 |
| Moisture Absorption (24 hr immersion) | 0.13% | ASTM D570 (Low) |
| Flammability | UL94 HB | Slow burning |
| Standard Sheet Sizes (Canadian Stock) | 48" x 96", 60" x 96", 48" x 120" | 1220 x 2440 mm / 1524 x 2440 mm |
| Thickness Range | 0.020" (0.5 mm) to 0.500" (12.7 mm) | Common: 0.060", 0.080", 0.093", 0.118", 0.187", 0.236", 0.375" |
| Thickness Tolerance | ±10% (≤0.125"), ±8% (0.126"–0.250"), ±6% (>0.250") | ASTM D374 |
| Flatness Tolerance | 0.125" over 48" length | Typical for extruded sheet |
| Surface Finish | Glossy both sides (standard) | Matte/anti-glare available on one side |
Machinability, Tooling & Feeds
| Operation | Tooling Recommendation | Parameters & Feeds |
|---|---|---|
| CNC Routing | Single-flute or O-flute carbide, 10°–15° helix | 12,000–18,000 RPM / 100–200 IPM (0.125" sheet). Climb milling preferred. |
| Sawing | Carbide-tipped, 60–80 teeth, triple-chip grind (TCG) | 3,000–4,000 SFM |
| Drilling | 118° point angle bits, slow pecking (0.010"–0.020" per peck) | Coolant mist required to prevent melting. |
| Laser Cutting | CO₂ laser | 80–120 W power / 10–20 mm/s speed. Clean edges with minimal char. |
| Thermoforming | Pre-drying not required if stored properly | 160°C–180°C (320°F–356°F). Avoid excessive heat buildup. |
| General Machining | Sharp tooling critical to avoid gumming | Use air blast or mist coolant. Chip evacuation essential. |
Common Defects & Quality Control
| Defect | Description / Cause | QC Check / Acceptable Level (ASTM D4802) |
|---|---|---|
| Surface Scratches | Improper handling or packaging | Visual under diffused light. Minor scratches <0.001" depth allowed. |
| Die Lines | Longitudinal streaks from extrusion die imperfections | Visual inspection. Should not be visually prominent. |
| Gels / Fisheyes | Unmelted resin particles causing optical imperfections | < 5 per sq ft, < 0.5 mm diameter allowed. |
| Contamination | Dust or foreign particles embedded during extrusion | Visual inspection against standard. |
| Thickness Variation | Exceeding ±10% tolerance, especially near edges | 9-point micrometer check (corners, edges, center). |
| Warpage | Uneven cooling or residual stress | Flatness check on granite table with feeler gauge. |
| Yellowing | Excessive heat exposure or UV degradation | Visual check. Ensure UV-stabilized grade for outdoor use. |
| Moisture Bubbles | Material not dried properly before thermoforming | Rare with PETG if stored correctly. Check preheat cycle. |
Storage, Handling & Racking Guidelines
Store PETG sheets flat on a clean, dry surface, ideally on a wooden or plastic pallet with a protective interleaf (polyethylene film or paper). Avoid stacking more than 6 sheets of 0.125" thickness or 3 sheets of 0.250" to prevent bowing. Keep in a climate-controlled environment (18°C–24°C, 40–60% RH) away from direct sunlight and heat sources. Do not store near solvents, adhesives, or plasticizers that may cause crazing.
For vertical racking, use padded A-frame racks with a 10°–15° tilt and secure with straps to prevent sliding. Always handle with clean cotton gloves to avoid fingerprints and scratches. Remove protective film immediately before fabrication; do not leave film on for extended storage (>30 days) as it may bond. For long-term storage, wrap in opaque polyethylene and seal edges with tape to prevent dust ingress. FIFO (first-in, first-out) rotation is recommended; label each bundle with date received and thickness.