Quick3D Flame retardancy (UL 94)
UL 94 ratings show whether a plastic stops burning once the flame is removed. Learn what V-0, V-1, V-2 and HB mean and how to read them.
What it means in practice
UL 94 is the most widely used flammability rating for plastics. It does not mean a material cannot burn. It describes how a small sample behaves after a test flame is removed: does it go out on its own, how quickly, and does it drip burning material?
Key takeaways
- UL 94 rates how a small sample behaves once a test flame is removed.
- V-0, V-1 and V-2 differ in burn time and burning drips; HB is the lowest rating.
- A rating always applies at a stated thickness; thinner walls usually burn more easily.
- A material rating does not certify your product; test the final part.
It matters most for:
- Enclosures for power supplies, chargers and control electronics.
- Cable clips, connectors and parts near wiring.
- Interior parts for vehicles, trains and aircraft, which follow their own sector standards as well.
- Parts near heaters, lamps or motors.
How it’s measured
For the vertical test, a bar is held upright and a small flame is applied to its lower end for 10 seconds, then removed. Once it stops burning, the flame is applied again. Testers time the afterflame and note whether burning drips ignite a pad of cotton below. Five bars make up a set.
- V-0: each bar stops burning within 10 seconds, and no burning drips ignite the cotton.
- V-1: each bar stops within 30 seconds, with no igniting drips.
- V-2: as V-1, but burning drips may ignite the cotton.
- HB: a horizontal test. The bar burns slowly enough to pass. It is the lowest rating.
- 5VA and 5VB: tougher tests with a larger flame, used for some enclosures.
Watch out
The rating has no units. It is always tied to a stated thickness.
How to read and compare it
- Thickness is part of the rating. “V-0 at 1.5 mm” does not mean V-0 at 0.8 mm. Thinner walls usually burn more easily. Check the thinnest wall in your design.
- Base resin vs printed part. Some ratings refer to the raw polymer, not a printed bar. Infill, gaps and layer lines can change how a printed part burns.
- Listed vs tested. A material listed with UL has been tested and is followed up by UL. A sheet that says “tested to UL 94” may mean an in-house test. Both are useful; they are not the same.
- Colour and additives. A rating may apply only to certain colours or grades.
- Trade-offs. Flame-retardant additives can lower toughness or change print behaviour.
- Your part, your approval. A material rating does not certify your product. If your part must meet a fire standard, it needs to be tested or approved in its final form.
Listed with UL
Tested, then followed up by UL.
“Tested to UL 94”
May be an in-house test. Useful, but not the same.
In our catalog
UL 94 ratings are text, so there is no numeric range. Materials rated V-0, V-1 or V-2 carry our flame-retardant badge:
- All flame-retardant materials: 37
- Filaments: 31
- Resins: 4
- High-performance materials: 23
Heat resistance of these materials: 58–237 °C (中位数 139.5 °C，共 32 种材料) (heat deflection temperature, mixed test loads).
Tip
Open each material to see its exact rating, the thickness tested, and whether the value is for the base resin.
Related properties
- Heat deflection temperature — holding shape near heat.
- Dielectric strength — insulation for electrical housings.
- Surface resistivity and ESD — static control for electronics.
- Glass transition temperature — where the material starts to soften.
For design advice, see flame-retardant parts.