PETG
Selecting and qualifying PETG sheet and printed parts using grade-specific forming, moisture, mechanical and exposure data.
Tags: materials, polymers, thermoplastics
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Identity and material record
Plaskolite's VIVAK PETG vacuum-forming guide gives 280–320°F (about 138–160°C) sheet temperature and 130–140°F (about 54–60°C) mold temperature. Measure the sheet and mold separately. Use the guide for the named sheet and verify temperature uniformity in the actual forming setup. Plaskolite VIVAK fabrication guide
PETG means polyethylene terephthalate modified with glycol. Prusa explains that this modification changes brittleness, printability and transparency relative to unmodified PET. The abbreviation alone does not identify an approved sheet, filament, color or finished-part process. Record the producer and full grade, supplied form, thickness or filament diameter, color/additives and manufacturing route. Prusa, PETG material guide
Sheet grade, optics and exposure
Plaskolite positions VIVAK PETG for indoor fabricated and thermoformed applications. Its catalog reports 86% total light transmission and 1.0% haze under ASTM D1003, and a relative density of 1.27 under ASTM D792. These are product data, not a guarantee of optical quality after forming, bonding or scratching. The same catalog says VIVAK is produced from resin complying with FDA food-contact requirements; obtain the applicable declaration and conditions for the exact sheet and finished assembly. Plaskolite, VIVAK catalog
Exposure protection is a grade choice: Plaskolite's regional PETG sheet range distinguishes non-UV-protected PETG for indoor use from PETG UV, coextruded with UV protection on both sides. This does not establish a common outdoor lifetime for all PETG or transfer an outdoor claim to filament. Specify exposure duration, retained appearance and mechanical acceptance criteria for the actual product. Plaskolite, PETG regional product range
For a clear cover, define haze, viewing distortion, surface finish and scratch acceptance on the finished part. For a machine guard, qualify the relevant impact and attachment requirements on the actual assembly; a material trade name or transparency measurement is insufficient.
Thermoforming and fabrication
The VIVAK fabrication guide gives a typical sheet temperature of 280–320°F, approximately 138–160°C, for vacuum forming, with a mold guideline of 130–140°F, approximately 54–60°C. These refer to different objects; neither is a universal oven-air setting. The guide calls for heat uniformity through the sheet and slower heating of heavier gauges. Its troubleshooting notes connect overheating with bubbles and bending too cold with a stressed, weakened part. Plaskolite, VIVAK fabrication guide, pp. 6, 9
The same guide emphasizes supporting sheet during cutting, maintaining sharp tools and avoiding vibration-induced cracking. It warns that solvent bonding reduces bonded-edge impact performance and that flame polishing can cause long-term edge cracking. Qualify an edge treatment or joint as part of the component, rather than assuming that an attractive edge preserves the original sheet's toughness. Plaskolite, pp. 2–3, 12–13
For repeat production, retain the sheet grade and gauge, extrusion orientation, heating arrangement, measured forming condition and final wall-thickness checks. Inspect corners, trimmed edges and mounting holes, not only the broad flat surface. Establish tolerances after the approved cooling and conditioning sequence.
A bounded printed-material example
Prusament PETG's technical data sheet reports the following typical results. Preserve its column labels when using them; “vertical xz” is the manufacturer's depicted specimen orientation, not a claim about every part loaded through layer interfaces.
| Test | Horizontal | Vertical xz |
|---|---|---|
| Tensile yield strength, ISO 527-1 | 47 ± 2 MPa | 50 ± 1 MPa |
| Tensile modulus, ISO 527-1 | 1.5 ± 0.1 GPa | 1.6 ± 0.1 GPa |
| Notched Charpy, ISO 179-1 | 6 ± 1 kJ/m² | 3 ± 1 kJ/m² |
Specimens used an Original Prusa i3 MK3, Slic3r Prusa Edition 1.40.0, 0.20 mm layers, two perimeters, 100% rectilinear infill, no top/bottom solid layers, 250°C nozzle and 80°C bed. The sheet separately reports interlayer adhesion of 18 ± 4 MPa using a Prusa Polymers method. These are comparison data, not allowable design stresses. Prusament PETG TDS, version 1.1, pp. 2–3
A printed bracket therefore needs its own build orientation, wall/infill structure, interface loading and acceptance test recorded. Reprinting the same CAD shape with another profile is a process change, even when the spool label is unchanged.
Moisture and printing process control
Prusa's drying guidance lists 55°C for six hours for its Prusament PETG, warns against exceeding the listed temperatures, and discusses spool construction limits. It recommends closed storage with desiccant; it also warns that an imprecise oven can damage filament. Wet material may produce poor surfaces, bubbles or reduced layer adhesion. Apply the filament maker's instructions to the exact product and spool, not a sheet-forming temperature or another polymer's drying cycle. Prusa, Drying filament
Prusa also warns that PETG can adhere strongly enough to damage smooth PEI print sheets, recommending textured or satin sheets in its PETG guide. Treat bed-surface preparation as part of the printer/material combination. Prusa, PETG guide
Thermal design and a calculated example
Eastman's Spectar 14471 typical data report ISO 75 deflection temperatures of 72°C at 0.45 MPa and 68°C at 1.80 MPa. Its ASTM D696 expansion coefficient is 7 × 10⁻⁵/°C. Eastman states that final performance depends on design, processing and pigmentation; these values do not guarantee shipment properties. Eastman, Spectar 14471 technical data
Calculated illustration: assuming that coefficient remains applicable, an unconstrained 1,000 mm length experiencing a uniform 20°C increase expands by:
ΔL = α × L × ΔT = 0.000070/°C × 1,000 mm × 20°C = 1.4 mm.
This is free expansion, not a mounting-clearance prescription: restraint, frame expansion, local heating and manufacturing variation still require evaluation. Likewise, a deflection-temperature test is not a continuous-use rating or permission to operate just below the reported value.
Handling and source dates
VIVAK's SDS identifies burn hazards from hot material, irritating decomposition fumes and dust exposure; it calls for ventilation/exhaust and avoiding dust generation. Use current safety information for the supplied sheet, filament, adhesives and cleaning chemicals separately. Plaskolite, VIVAK SDS, §§2, 7–8
The fabrication guide prints ©2025, code 082025. The VIVAK SDS explicitly gives 10 February 2023 as its revision date. Prusament TDS version 1.1 explicitly says last update 16 February 2022; the filename or upload location is not its revision date. The cited live product and help pages show no technical document revision date.