PETG Properties — Mechanical, Optical & Thermal Datasheet
PETG's property profile is defined by its amorphous structure: excellent optical clarity, good impact resistance, moderate stiffness, and easy thermoformability — combined with lower temperature resistance and lower modulus than semi-crystalline engineering plastics. This datasheet covers mechanical, optical, thermal, electrical, and chemical resistance properties for standard PETG sheet, rod, and tube.
At a glance:
- Tensile strength: 7,700 psi; flexural modulus: 310,000 psi
- Light transmission: >90%; haze: <5% — optically comparable to acrylic
- Heat deflection temp (264 psi): 155°F (68°C); Tg: ~176°F (80°C)
- Izod impact, notched: 1.5–2.0 ft·lb/in — 3–4× higher than standard acrylic
- FDA 21 CFR 177.1630 compliant; RoHS compliant
- Not a bearing or wear material — see PET-P (Ertalyte) for that application class
Mechanical Properties
PETG's stiffness (flexural modulus ~310,000 psi) is roughly half that of bearing-grade PET-P (Ertalyte, 600,000 psi) and significantly lower than acrylic (450,000 psi). This reflects the amorphous structure — without crystalline regions to reinforce the matrix, stiffness is limited.
What amorphous structure provides instead is toughness: the polymer chains are less rigidly constrained and can deform under impact without catastrophic crack propagation, giving PETG its advantage over acrylic in impact resistance.
Tensile and Flexural Data
Impact and Hardness
PETG vs Acrylic vs Polycarbonate — Mechanical
Thermal Properties
PETG's amorphous structure means there is no crystalline melting transition — it softens gradually across a range of temperatures, which is exactly what makes it easy to thermoform.
PETG's continuous use limit of ~140°F (60°C) is the most important thermal specification. Applications in direct sunlight through glass, near heat sources, or in hot environments can easily exceed this limit and cause distortion. For higher-temperature clear applications, consider polycarbonate (240°F) or acrylic (165°F).
Thermoforming Characteristics
PETG's amorphous structure gives it a wide, forgiving thermoforming window:
- Forming temperature: 280–340°F (oven air temp); part surface 240–280°F at forming
- Minimum radius: Tighter radii achievable than acrylic without crazing; PETG rarely stress-whitens at bends
- Draw depth: Handles moderate draw ratios (up to 1:1) without significant wall thinning
- Cooling: Air cooling adequate; no quenching required
- Shrinkage: 0.3–0.5% typical; account for CTE in pattern dimensions
For display fabricators and packaging thermoformers, PETG's forming characteristics are significantly more forgiving than those of acrylic, making it easier to achieve complex shapes without defects.
Optical Properties
This is PETG's defining strength for display and glazing applications.
PETG's light transmission is comparable to acrylic (typically >92%) and better than standard polycarbonate, which can show slight yellowish tint and has higher haze due to molecular structure. PETG does not yellow significantly in indoor conditions; outdoor UV exposure causes gradual yellowing over months to years without UV stabilization.
For applications requiring UV resistance, specify UV-stabilized PETG (some sheet suppliers offer UV-absorbing grades) or switch to UV-stabilized acrylic.
Electrical Properties
PETG is a good electrical insulator. Its static charge accumulation (triboelectric charging) can be an issue in clean or dusty environments — anti-static coatings or topical treatments are available from fabricators.
Chemical Resistance
PETG's chemical resistance is one of its advantages over polycarbonate. Polycarbonate is attacked by esters, ketones, aromatic hydrocarbons, and many cleaning agents; PETG resists most of these.
| Reagent | PETG Resistance | Notes |
|---|---|---|
| Water | Excellent | Very low absorption |
| Dilute acids (pH > 3) | Good | Acetic, citric, phosphoric |
| Dilute alkalis (<10% NaOH) | Good | |
| Alcohols | Good | IPA, ethanol (limited immersion) |
| Acetone | Poor | Attacks PETG |
| MEK | Moderate | Used as a bonding solvent; controlled contact OK |
| Aromatic hydrocarbons | Moderate–Poor | Toluene, xylene cause swelling |
| Polycarbonate cleaning sprays | Good | Unlike PC, PETG resists most PC-safe cleaners |
| Chlorinated solvents | Poor | Methylene chloride attacks PETG |
| Gasoline / diesel | Poor | |
| UV (outdoor) | Moderate | Gradual yellowing; specify UV-stabilized grade |
Physical Properties
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Frequently asked questions — PETG FAQ