UL 94 Standard & Flame-Retardant Prototyping Materials

Flammability testing UL 94

RpProto offers all materials meeting UL94V0 standards for rapid prototyping and production for CNC machining (ABS and PC), vacuum casting (Hei-cast 8260) and injection molding. UL94 materials allow machined or thermoplastic molded plastic parts to pass real-world testing as they can be used in environments containing flammable products.

UL 94 rating is the most commonly used standard for flammability of plastic materials. Used to evaluate the ability of a material to extinguish once ignited. The standard classifies plastics in six different classes, from least flame retardant to most flame retardant, according to their burning behavior in different directions and part thicknesses.

There are many evaluation methods depending on the burning speed, burning time, anti-drip ability and whether the dripping beads burn. Each measured material can have many values ​​depending on its color and thickness. When choosing a material for a product, its UL rating must meet the wall thickness requirements of plastic parts. A UL rating must be specified along with a thickness value.

Introduction of UL 94

Flame retardant ratings of plastic materials increase from HB, V-2 and V-1 to V-0:

HB : The lowest flammability rating of the UL 94. It is necessary that for samples with a thickness of 3 to 13 mm, the burning speed is less than 40mm per minute; and the burning speed is less than 70 mm per minute for samples thinner than 3 mm thick, or the flame is extinguished before the 100 mm.

V-2 : After two tests of burning the sample for 10 seconds, the flame is extinguished within 30 seconds and cotton can be ignited at a depth of 30 cm below.

V-1 : After two tests of burning the sample for 10 seconds, the flame was extinguished in 30 seconds and couldn’t light the cotton located at a depth of 30 cm below.

V-0 : After two 10-second burning tests at the specimen, the flame goes out after 10 seconds.

Flammability Test for UL 94 HB
Flammability Test for UL 94 HB

The flame retardant grade of plastic is gradually increased from HB, V-2, V-1, V-0, 5VB to 5VA:

RatingsOrientation of Test SampleDescriptionAllowed
Burning Time
Allowable Particle
Drop Flaming
Allowable  Particle Drop
UL 94 HBHorizontalSlow BurningBurning ends before 100mm and at a rate of less than 76mm per minute for samples no thicker than 3mm.
UL 94 V-2VerticleBurning Stops30 SecondsYesYes
UL 94 V-1VerticleBurning Stops30 SecondsNoYes
UL 94 V-0VerticleBurning Stops10 SecondsNo Yes
UL 94 5VBVerticleBurning Stops60 Seconds No No
UL 94 5VAVerticleBurning Stops60 Seconds No No

Flammability effect

Dyes/Additives: For ideal outcomes, choose an additive-free base resin because most additives do not have a UL certification, If you need a certain additive, you’ll probably need to work with a customisable mixer to make a flame retardant blend of the base resin, such as color matching.

Part Thickness: The UL rating is measured at different thicknesses, which can dramatically change the UL rating of your part. If you are looking for UL 94 V-0 material for a thin-walled or thick-walled part in following table. So pay attention to the thickness of the wall and the choice of material.

Thickness Test 
Flammability Rating UL 94
0.0295 V-2 
0.0591 V-0 

UL 94 V-2, UL 94 V-1, UL 94 V-0

As judged by the vertical burning test, the upper end of the strip test piece is placed vertically, and a gas lamp flame is applied to the lower end thereof for 10 seconds. If the flame goes out after releasing the gas hob flame, immediately relight the gas hob flame for another 10 seconds before extinguishing the flame. According to the total time of flaming combustion and the presence or absence of ignition caused by dripping (particles falling from the test piece), the judgments are 94V-2, 94V-1, 94V-0 in descending order of flammability.

Specimen shall be 5 inches (127 mm) long, 0.5 inches (12.7 mm) wide, and five thicknesses from smallest to largest 0.5 inches (12.7 mm). Each thickness increment shall not exceed 0.125 in. (3.18 mm). 

Flammability Testing for UL 94 V0
Flammability Testing for UL 94 V0

UL 94 V-0 Rated Plastic Materials

RpProto offers machined or vacuum cast plastic parts that meet UL 94 V-0 testing, enabling the creation of plastic prototypes that can be used for functional and visual testing.

These classifications relate to materials commonly used in the manufacture of home appliance housings, structural components, and insulators (UL 94 5VA, 5VB, V-0, V-1, V-2, HB).

UL 94 V-0 materials are especially popular in electronic equipment, such as electrical cable jacketing.

UL 94 V-0 PART
UL 94 V-0 PART
 UL 94 V-0 Materials for Injection Mold
ABSPolylac PA-765
ABS/PC Bayblend FR110, Bayblend FR 3010, Cycoloy C2950 and Cycoloy C6600
LCPVectra E130i (30% glass fiber)
PARTP 203 FR (20% glass nylon)
PBTValox 420SEO (30% glass fiber)

Lexan 940 and Lexan 3412R (20% glass fiber)


Victrix 450G


Maxxam FR PP 301


Ryton R-4 (40% glass fiber)


Radel R-5000 NT


Santoprene 251

For any further questions regarding whether a material or part conforms to UL classification, please contact us at [email protected]

Get quote for UL 94 V-0 plastic parts now.

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