PET vs PETG
PET and PETG are close cousins — PETG is PET with a glycol modification that changes how it processes. PET is the rigid, crystalline polyester behind bottles, fibers and food packaging. PETG trades a little stiffness and heat resistance for amorphous clarity, impact toughness and far easier 3D printing and thermoforming, making it the go-to for clear guards and printed parts.
The verdict
Choose PET for packaging, fibers and rigid parts where higher stiffness and a slightly higher heat rating (~70°C nominal) help. Choose PETG when you need easy 3D printing or thermoforming, better impact toughness and crack resistance, and excellent clarity — at the cost of a touch lower stiffness and heat resistance (~65°C nominal).
Side-by-side data
| Property | PET | PETG |
|---|---|---|
| Category | Engineering Plastic | Engineering Plastic |
| Density (g/cm³) | 1.38 | 1.27 |
| Tensile strength (MPa) | 55 | 50 |
| Yield strength (MPa) | 50 | 48 |
| Elongation (%) | 70 | 120 |
| Hardness | R106 | R108 |
| Max service temp (°C) | 70 | 65 |
| Machinability | ●●●●● | ●●●●● |
| Corrosion resistance | ●●●●● | ●●●●● |
| Relative cost | ●●●●● | ●●●●● |
| Thermal cond. (W/m·K) | 0.24 | 0.2 |
| Typically used for | Bottles, fibers & food packaging | Clear guards & 3D-printed parts |
Which should you choose?
Choose PET when…
- The part is bottles, food packaging, fibers or rigid trays
- You want higher stiffness — ~55 MPa tensile versus PETG's ~50
- A slightly higher service temperature (~70°C nominal vs 65°C) helps
- The process is injection molding or extrusion, not 3D printing
- Crystalline PET's barrier properties matter for packaging
- You need the lower-creep, more dimensionally rigid polyester
Choose PETG when…
- You're 3D printing — PETG lists 3D Printing as a process and prints far more easily than PET
- Parts are thermoformed into clear guards, face shields or display covers
- Impact toughness and crack resistance matter — PETG's ~120% elongation vs PET's ~70%
- Excellent optical clarity in thick or formed sections is required
- Top corrosion/chemical resistance (5 vs 4) is a plus
- You want fewer brittle failures in handling and assembly
Key differences that matter
- PETG is the glycol-modified, amorphous version of PET — easier to form and less prone to crystallizing or hazing when thermoformed.
- PETG is much more ductile (~120% elongation vs ~70%), giving better impact and crack resistance.
- PET is slightly stiffer (~55 vs 50 MPa tensile) and rated a bit higher in temperature (~70 vs 65°C nominal).
- Only PETG lists 3D Printing as a process here — it's a mainstream FDM filament, while PET is harder to print well.
- Both share low cost (1.5) and good chemistry resistance; PETG edges it at corrosion 5 vs 4.
- Neither is a high-temperature plastic — both stay below ~70°C nominal continuous, ruling them out of hot service.
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Open the Material SelectorGet a Quote →Frequently asked questions
Why is PETG easier to 3D print than PET?
PETG is amorphous and stays clear and stable through the melt-and-cool cycle, with a wider processing window and less warping or crystallization. PET tends to crystallize, haze and shrink unpredictably when printed, demanding tight control. That's why PETG is a standard FDM filament and PET typically isn't used raw for printing.
Is PETG stronger than PET?
Not in stiffness — PET is slightly stronger and more rigid (~55 vs 50 MPa tensile nominal). PETG wins on toughness: its much higher elongation (~120% vs ~70%) means it absorbs impact and resists cracking far better. So PET is stiffer, PETG is tougher — pick based on whether you fear bending or fear shattering.
Can either handle hot liquids or dishwashers?
Not really. PET tops out near 70°C and PETG near 65°C continuous (nominal). Dishwashers and hot fills routinely exceed that, so both can soften or distort. For repeated hot-water or steam exposure you need a higher-temperature plastic such as PSU, PPSU or PEEK rather than either polyester.
Which is clearer for a display or guard?
PETG, especially in thick or thermoformed sections. Being amorphous, it stays optically clear without the haze PET can develop when formed or crystallized. PETG also resists cracking during fabrication, so machine guards, face shields and display covers commonly use it over PET.
Property values are typical/nominal figures for early-stage guidance only and vary by temper, grade, supplier and heat treatment. Confirm critical specifications against a certified datasheet or with an mfgiq engineer before production.