UL94 is a plastic flammability standard issued by Underwriters Laboratories. This standard is based on different thicknesses
Plastic burning conditions to classify plastics. The classification from the lowest (minimum flame retardancy) to the highest
(maximum flame retardancy) is:
- HB: Slowly burns on horizontally placed samples, burning at less than 75 mm/min for materials less than 3 mm thick
- V2: Stop burning within 30 seconds of the sample placed vertically, allowing the particles to be dripped
- V1: Stop burning within 30 seconds of the sample placed vertically, allowing the dropping of non-burning particles
- V0: Stop burning within 10 seconds of the sample placed vertically, allowing to drop non-burning particles
- 5VB: Stop burning within 60 seconds of the sample placed vertically, not allowed to drip, allowing holes to appear on the sample
- 5VA: Stop burning within 60 seconds of the sample placed vertically, no dripping is allowed, and holes are not allowed on the sample.
The test is performed, and the intensity of the flame is about five times that of other materials. There are other classifications for low density
foams. (HF-1, HF-2, HBF) and film (VTM-0, VTM-1, VTM-2).