Flammability

Flammability for plastics thicker than 0.050 in. if the specimen does not ignite, it is classed non-burning by this test. If the specimen continues to burn, it is timed until it stops or a 4 in. mark is reached. A specimen which burns to the 4 in. mark is classed as burning by this test and the rate is equal to (180/time) in. per min. If the specimen does not continue burning to the 4 in. mark, it is classed as self-extinguishing and the length of the burned portion is reported as the extent of burning.

The specimen is clamped at one end on a ring stand so the longitudinal axis is horizontal and the transverse axis is inclined 45° to horizontal. A piece of 20-mesh Bunsen burner gauze is clamped horizontally 3/8 inch below the specimen. A Bunsen burner, placed so the flame contacts the end of the specimen, is held 30 seconds and then removed. If the specimen does not ignite, the burner is returned for another 30-second attempt. The burning is measured along the lower edge of the specimen. ASTM D-635.