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PETG

Engineering $$

Glycol-modified polyethylene terephthalate. Amorphous copolyester produced by partial substitution of ethylene glycol with cyclohexane dimethanol (CHDM) — the modification suppresses crystallization, giving transparent thermoformable sheet, good impact strength, and excellent thermoforming behavior across a wide processing window. PETG is the workhorse clear thermoformable plastic for retail display, signage, medical device housings, and FDM 3D printing. Easier to process than PC and acrylic, tougher than acrylic, more chemically inert than PC. The cost: lower temperature capability than PC (HDT ~70°C).

Service °C
65–70°C continuous (149–158°F) — the major limitation
Tensile
48–55 MPa (7,000–8,000 psi)
Density
1.27–1.30 g/cm³ (0.047 lb/in³)
Cost
$$
$2.00/lb
Trade names: Spectar (Eastman, sheet)Vivak (Bayer / Sabic, sheet)Tritan (Eastman — distinct copolyester, marketed alongside PETG)Eastar (Eastman)Skygreen (SK Chemicals)PETG filament — wide variety of 3D-printing brands

Glycol-modified polyethylene terephthalate. Amorphous copolyester produced by partial substitution of ethylene glycol with cyclohexane dimethanol (CHDM) — the modification suppresses crystallization, giving transparent thermoformable sheet, good impact strength, and excellent thermoforming behavior across a wide processing window. PETG is the workhorse clear thermoformable plastic for retail display, signage, medical device housings, and FDM 3D printing. Easier to process than PC and acrylic, tougher than acrylic, more chemically inert than PC. The cost: lower temperature capability than PC (HDT ~70°C).

Properties

Mechanical
Mechanical properties for PETG
Tensile48–55 MPa (7,000–8,000 psi)
Yield45–53 MPa
Elongation110–180% (much more ductile than acrylic; comparable to PC)
Modulus2.0–2.4 GPa (290,000–350,000 psi)
Flexural70–85 MPa (10,000–12,000 psi)
Compressive50–75 MPa (7,300–10,900 psi)
HardnessRockwell R120 / Shore D 78
Izod impact60–110 J/m notched (1.1–2.1 ft·lb/in); much better than acrylic, less than PC
Poisson's ratio0.42
Thermal
Thermal properties for PETG
Continuous max65–70°C continuous (149–158°F) — the major limitation
Short-term max75–85°C short-term
Min service-40°C — PETG retains toughness at cold temperatures
Conductivity0.27–0.32 W/m·K
CTE60–75 × 10⁻⁶/°C (33–42 × 10⁻⁶/°F)
Specific heat1200 J/kg·K
Plastic-specific
Crystallinityamorphous
Tg78–85°C (172–185°F) — the upper service limit
HDT65–72°C at 1.82 MPa / 70–80°C at 0.45 MPa (D648)
UL RTI~60°C (UL RTI)
Moisture (sat)0.13–0.30% at saturation
Water (24hr)0.13–0.20% (24hr immersion)
LOI23%
UL94HB
µ (friction)0.3

Variants (5)

PETG (Standard Copolyester Sheet) PETG-standard
Trade: Eastman Spectar, Sabic Vivak, Skygreen

Standard glycol-modified PET copolyester sheet for retail display, signage, thermoforming, medical packaging, and machine guards. Property data above represents this variant.

UV-Stabilized PETG (Outdoor Sheet) PETG-UV
Trade: Spectar UV, Vivak UV

UV-stabilized PETG for outdoor signage, exterior architectural panels, and weatherable display applications. 5–10+ year outdoor lifetime vs. 1–2 years for unstabilized.

Tritan Copolyester (Premium PETG-class) Tritan
Trade: Eastman Tritan

Eastman's premium copolyester — distinct chemistry with higher CHDM substitution and additional comonomers. Higher HDT (100°C vs. 70°C standard PETG), higher impact, dishwasher-safe service. The reusable-water-bottle plastic (Nalgene Tritan); also used for medical devices requiring higher service temperatures.

PETG FDM 3D-Printing Filament FDM-filament
Trade: Generic PETG (many brands), Prusament PETG, Hatchbox PETG, Atomic Filament PETG

FDM filament grade — slightly modified chemistry for stable extrusion, layer adhesion, and pickup-free spooling. The dominant "engineering plastic" in beginner-to-intermediate FDM printing because of its forgiving processing window and reasonable mechanical properties.

Medical Tritan / Eastman MD Series medical-Tritan
Trade: Eastman MD-1 / MD-2 / MD-3, Eastman MX series

Medical-grade Tritan copolyester for surgical instrument handles, IV access devices, and reusable medical components. ISO 10993 biocompatibility tested; gamma and EtO sterilization compatible. BPA-free is the principal marketing advantage vs. PC.

Processing

Machinability: good
Chip: Continuous chips with sharp tooling — PETG is more ductile than acrylic or PS and cuts more like polycarbonate than like a brittle plastic.
Gumming: Moderate. PETG Tg is ~80°C — relatively low — so friction heat from dull tooling will smear the surface. Sharp tools and adequate chip clearance prevent gumming.
Finish: 16 Ra readily with sharp tooling; flame polishing produces optically clear edges similar to acrylic finishing.
Tooling: Sharp carbide, neutral to positive rake. Speed 300–800 SFM (slightly slower than acrylic), feed 0.005–0.012 in/rev. Watch for stress crazing on aggressive cuts — PETG, like all amorphous plastics, can craze under combined heat and tensile load.
Annealing at 65–70°C for 1 hr/inch of section thickness after heavy machining significantly reduces stress-crazing. PETG bonds well with solvent (methylene chloride, MEK) and with cyanoacrylates and structural acrylic adhesives. Mechanical fasteners, snap fits, and ultrasonic welding are all standard joining methods.
Process compatibility
injection molding excellent
extrusion excellent
cnc machining good
fdm excellent
sla dlp not-applicable
sls not-applicable
mjf not-applicable
thermoforming excellent
blow molding good
compression molding fair

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Additives
uv stabilizer (0.5–2% UV absorber + HALS package) — Spectar UV, Vivak UV are the canonical outdoor PETG sheets. UV-stabilized PETG competes with weatherable PC for outdoor signage and display applications.
impact modifier (low (PETG is already ductile)) — Tritan and similar premium copolyesters incorporate impact modification and additional CHDM substitution for higher impact and elevated HDT (Tritan reaches ~100°C HDT vs. PETG's 70°C).
flame retardant non halogen (10–20%) — FR-PETG exists but is less developed than FR-PC. For flame-rated transparent applications, FR-PC is generally the better choice.
antistatic carbon (depends) — Niche grade for cleanroom and ESD-controlled applications. Loses PETG's clarity advantage.

Chemical resistance

acids good Resistant to dilute acids at room temperature. Concentrated oxidizing acids attack PETG.
bases fair Slightly better than PET in alkalis due to glycol modification, but strong alkalis at temperature still hydrolyze PETG. Avoid sustained caustic cleaning.
aliphatic Solvents good Resistant to hydrocarbons, oils, fuels at room temperature.
aromatic Solvents poor Aromatics (toluene, xylene) swell PETG and are used as solvent cements. Avoid sustained exposure.
fuels Oils good Good at room temperature; some swelling possible at elevated temperature.
hot Water Steam fair PETG resists hydrolysis better than PET due to glycol modification, but service above 60–70°C in water is approaching the thermal deformation limit. Not for hot-fill or steam.
alcohols fair Isopropanol and ethanol cause stress crazing under load. Disinfectant-wipe-induced crazing is documented in medical device housings.
PETG's chemical resistance is moderate — better than PC and PS in most chemistries, much weaker than PP or HDPE in solvents and bases. The alcohol/disinfectant crazing issue is the most-cited field problem, especially in medical device housings cleaned with IPA wipes.
⚠ Stress-cracking agents
Alcohols under stress (isopropanol, ethanol — disinfectant wipes)Ketones (acetone, MEK — used as PETG solvents)Chlorinated solvents (methylene chloride, chloroform — solvents)Aromatic hydrocarbons (toluene, xylene — sustained exposure)Strong alkalis at elevated temperature (similar to PET, less severe)Hot water (limited; less hydrolysis-prone than PET due to CHDM)

Regulatory

✓ FDA grade
✓ NSF 51
○ NSF 61
○ USP Class VI
✓ RoHS
✓ REACH
✓ EU 10/2011
HB UL94 best

FDA-compliant PETG grades (Spectar, Vivak) are widespread — PETG is standard for medical device housings, blister packaging, and pharmaceutical primary packaging. Tritan (related copolyester) was developed specifically as a BPA-free transparent food/beverage plastic and dominates reusable water bottles. PETG is BPA-free by chemistry (no bisphenol-A in the formulation), a key marketing distinction vs. PC. UL94 HB only — PETG is flammable; FR grades exist but are less common than for PC. NSF 61 (potable water) certification is rare for PETG.

Notes & applications

Overview

PETG is what PET becomes when partial substitution of the ethylene glycol backbone with cyclohexane dimethanol (CHDM) suppresses crystallization. The result is amorphous, transparent, easy to process, and significantly tougher than acrylic or polystyrene — at the cost of lower thermal capability than crystalline PET or polycarbonate.

The selection criteria for PETG:

  • vs. Acrylic (PMMA) — PETG is far less brittle (110%+ elongation vs. acrylic’s 4%), tougher in impact, easier to thermoform. Acrylic is harder, more scratch-resistant, slightly clearer, and tolerates higher outdoor exposure when UV-stabilized. Pick acrylic for static decorative use, PETG for parts that will be handled or impacted.
  • vs. Polycarbonate (PC) — PETG is cheaper, easier to thermoform, BPA- free by chemistry. PC has 2× the HDT, 5× the impact, and is more weatherable. Pick PC for safety glazing, impact-critical applications, and elevated-temperature service. Pick PETG for general clear parts, retail display, and FDM printing.
  • vs. PET (bottle or machined) — PETG is amorphous (clear); PET crystallizes (opaque in thick sections). PETG thermoforms over a wider window. PET handles higher temperatures and has slightly better mechanical properties.
  • vs. ABS — ABS is opaque (and stiffer in some grades) but tougher; PETG is clear. PETG largely displaced ABS as the easy-print FDM filament because of lower warpage.

The most-cited single PETG win is clear thermoforming and FDM printing on inexpensive equipment. Wider processing window, no warping issues that plague ABS, no scratch issues that plague acrylic.

Machining notes

PETG machines well — ductile, doesn’t shatter like acrylic, doesn’t gum like polyolefins (when tooling is sharp). Continuous chips with sharp tooling; 16 Ra finish readily.

Practical recipe:

  • Sharp carbide, neutral to positive rake
  • Speed: 300–800 SFM (slower than acrylic to avoid heat buildup)
  • Feed: 0.005–0.012 in/rev
  • Coolant: optional for light cuts, recommended for heavy

PETG bonds well — both solvent welding (methylene chloride, MEK) and structural adhesives (cyanoacrylates, two-part acrylics, epoxies) work. This is a major practical advantage vs. polyolefins and a key reason PETG dominates clear display fabrication.

Edge finishing: flame polishing or solvent vapor polishing produces optically clear edges similar to acrylic. PETG also accepts conventional diamond polishing for highest-quality finishes.

Stress-relief annealing at 65–70°C for 1 hr/inch reduces residual machining stress that can cause crazing in solvent-rich environments (disinfectant wipes, cleaning chemicals).

Variant selection guidance

  • Standard PETG (Spectar, Vivak) — the default for thermoforming, retail display, signage, medical packaging, machine guards. FDA grades widespread.
  • UV-stabilized PETG (Spectar UV, Vivak UV) — for outdoor signage and weatherable display applications. 5–10+ year outdoor life.
  • Tritan copolyester — premium PETG-class with higher HDT (100°C), higher impact, dishwasher-safe. Reusable water bottles, medical devices, kitchen appliances.
  • FDM filament grade — slightly tuned for extrusion stability. Beginner-friendly engineering filament.
  • Medical Tritan (MD-series) — USP Class VI biocompatibility for reusable medical components and surgical instruments.

Failure modes worth designing around

Heat distortion above 70°C is the defining PETG limitation. Standard PETG HDT is ~70°C at 1.82 MPa load; the material softens visibly between 70–85°C. Dishwasher cycles (75–80°C) deform PETG drinkware unless using Tritan. Sun-exposed enclosed spaces (cars, greenhouses) reach 60–80°C and PETG parts there deform within months. For temperature-tolerant clear parts, step up to PC or Tritan.

Stress crazing under alcohol contact — isopropanol and ethanol cause crazing in stressed PETG over hours to days. Disinfectant-wipe cleaning of stressed PETG medical device housings is a documented failure mode. Design with low-stress geometry, or specify PC for IPA-cleaned medical devices.

FDM layer-line failure — printed PETG fails at layer boundaries under flexural load far below isotropic material strength. Print orientation matters significantly; print parameters (nozzle temperature, layer height, cooling) tune layer adhesion. Annealing improves layer bond modestly.

UV degradation of unstabilized PETG is fast — yellowing within 1–2 years outdoors. UV-stabilized grades extend to 5–10 years but PETG is fundamentally an indoor or short-outdoor material vs. acrylic and weatherable PC.

Solvent crazing in general — like all amorphous polymers, PETG is susceptible to stress + solvent crazing. Most lab solvents (acetone, MEK, chloroform, methylene chloride) attack PETG; some are used as solvent cements. Avoid these in unstressed-PETG service paths.

Creep under sustained load — PETG cold-flows under continuous tensile or compressive load, less than polyolefins but more than glass-filled engineering plastics. Bolt preload relaxes; gasket seals creep. Spring loading or design margin required.

Applications by industry

  • Retail and display — POP signage, retail fixture parts, jewelry cases, display covers. PETG’s combination of clarity, easy thermoforming, and impact resistance makes it the default clear display plastic.
  • Medical and pharmaceutical — medical device housings, blister packaging, IVD diagnostic device shells, pharmaceutical primary packaging, prefilled syringe trays. FDA and USP Class VI grades.
  • 3D printing — FDM filament for prototyping, hobby printing, and end-use parts. The second most-printed material globally after PLA.
  • Food service — sneeze guards (massive demand spike 2020+), salad bar covers, deli case fronts, refrigerator interior parts. FDA grades.
  • Reusable drinkware — Tritan copolyester for sport bottles, baby bottles, lab squeeze bottles. The BPA-free clear plastic that displaced PC in this market segment.
  • Industrial machinery — clear machine guards, safety shields, inspection windows. Lower cost than PC and stiffer than acrylic in large thin panels.
  • Construction and architectural — decorative interior panels, illuminated signage, partition glazing. UV-stabilized for exterior use.
  • Consumer products — clear cosmetic packaging, transparent housewares, hobby-craft sheet stock.

Sources & standards

Standards: ASTM D4507 (Polyester molding and extrusion materials)FDA 21 CFR 177.1315 (PETG food contact)FDA 21 CFR 177.1630 (PET-class food contact)ISO 10993 (some grades, biocompatibility)USP Class VI (Tritan medical grades)NSF/ANSI 51 (food equipment)

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