UL 94 is a standard for the flammability of plastics published by Underwriters Laboratories. The standard classifies plastics according to how they burn in different directions and part thicknesses .

Ⅰ. Scope of application

1. This standard applies to the flammability test of plastic parts of equipment and electrical appliances

2. The final qualification of the material depends on its use in the overall equipment and is consistent with the standards applicable to the equipment

3. This standard can be used for other non-metallic materials; but not for building materials and decorative plastic materials

4. The methods described in this standard include standard size samples and are used only to measure and demonstrate the flammability of materials used in equipment and appliances with respect to heat and flame in a controlled laboratory environment

Ⅱ. Classification

HB, V-0, V-1, V-2, 5VA, 5VB, VTM-0, VTM-1, VTM-2, HBF, HF1, HF2 , where VTM-0, VTM-1, VTM-2 are suitable for Plastic film, HBF, HF1, HF2 are suitable for foaming materials

The grade testing scheme is as follows:

1) Class HB: Horizontal Burning Test

2) V0－V2 level: Vertical Burning Test

3) 5VA/5VB: 5V class fire test 500w (125 mm) Vertical Burning Test

4) RP Class: Radiant Panel Flame Spread Test

5) VTM0-VTM2: Thin Material Vertical Burning Test

6) HF1-HF2: Horizontal Burning Foamed Material Test

Ⅲ. Detailed explanation of authentication method

UL94 HB: Horizontal Burning

This plastic burns slowly but is not self-extinguishing. This type is the lowest rating of UL and is often used when vertical V0, V1 or V2 methods are not feasible.

UL94 V0, V1, V2, 5V: vertical combustion

UL94 V0 evaluation method: After the flame is removed from the ignition, the sample can quickly self-extinguish to no burning melt dripping within 10s (that is, the burning melt drips one foot below the test sample cotton pads, the cotton cannot be ignited).

The UL94 V1 evaluation method is similar to V0, except that it requires a longer self-extinguishing time. This test allows the melt to drip onto the cotton pad, but does not ignite the cotton.

UL94 V2 is the same as V1 except that it allows burning droplets to ignite cotton down to one foot below.

UL94 5V is the most stringent test method, which involves the actual life of plastic products in flames. The experiment requires that the flame length is 5in, and the test sample is burned five times, during which no molten droplets are allowed to drip, no obvious distortion of the test sample is allowed, and no burned holes can be produced.

The above is the introduction of UL 94 certification. If you need more detailed UL 94 test standard methods, SKYLINE’s SL-S29 Horizontal-Vertical Flame Chamber can provide more details of parameters.