UL94 fire rating classification standard
Flammability UL94 rating is the most widely used flammability performance standard for plastic materials. It is used to evaluate the ability of a material to extinguish after it has been ignited. There are various evaluation methods depending on the burning speed, the burning time, the drip resistance, and whether the beads are burned. Each material to be tested can obtain many values depending on the color or thickness. When a material of a product is selected, its UL rating should meet the thickness requirements of the wall portion of the plastic part. The UL rating should be reported along with the thickness value. It is not enough to report only the UL rating without thickness.
The flame retardant grade of plastic is gradually increased from HB, V-2, V-1 to V-0:
HB: The lowest flame retardant rating in the UL94 standard. For samples from 3 to 13 mm thick, the burning speed is less than 40 mm per minute; for samples less than 3 mm thick, the burning speed is less than 70 mm per minute; or it is extinguished before the 100 mm mark.
V-2: After two 10 second burn tests on the sample, the flame is extinguished within 30 seconds. It can ignite the cotton wool under 30cm.
V-1: After two 10 second burn tests on the sample, the flame was extinguished within 30 seconds. Do not ignite the cotton wool under 30cm.
V-0: After two 10 second burn tests on the sample, the flame is extinguished within 10 seconds. There can be no burning things falling.
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