Flammability UL94 Rating

The flammability UL94 rating is the most widely applied standard for the flammability performance of plastic materials. It is used to evaluate the ability of materials to extinguish after being ignited. There are various evaluation methods based on the burning rate, burning time, dripping resistance, and whether the dripping beads burn. Each tested material can obtain multiple values according to its color or thickness. When selecting the material for a certain product, its UL rating should meet the thickness requirements of the wall part of the plastic part. The UL rating should be reported together with the thickness value. It is not sufficient to only report the UL rating without the thickness. 

The flame retardant ratings of plastics increase progressively from HB, V-2, V-1 to V-0: 

HB: The lowest flame retardant rating in the UL94 standard. For samples with a thickness of 3 to 13 millimeters, the burning rate is required to be less than 40 millimeters per minute; for samples with a thickness of less than 3 millimeters, the burning rate is required to be less than 70 millimeters per minute; or the sample should extinguish before reaching the 100-millimeter mark. 

V-2: After two 10-second combustion tests on the sample, the flame extinguishes within 60 seconds. Combustible substances can drop. 

V-1: After two 10-second combustion tests on the sample, the flame extinguishes within 60 seconds. No combustible substances can drop. 

V-0: After two 10-second combustion tests on the sample, the flame extinguishes within 30 seconds. No combustible substances can drop.