Flammability classification and glow wire testing

Glow wire testing

The glow wire test according to IEC 60695 is used to test the flammability of plastic components. In this test, parts overloaded by a glow wire or glowing components are simulated. The specimen is held for 30 seconds against the glow wire. While this is done, it is checked whether the specimen starts to burn, how long it burns or whether burning material drops onto a sheet of tissue paper. The tissue paper must not be inflamed. The test temperature is between +650 °C and +960 °C.

Flammability classification

Flammability classification according to UL 94 is highly important. The flame of a Bunsen burner is used as source of fire, which is briefly brought in contact with the specimen twice. During the test, the burning time is measured, and any burning parts dropping on a cotton pad placed below the specimen are evaluated. The test results in classifications V (vertical) and HB (horizontal).

HB – in the horizontal flammability test, the material inflames slowly. While doing so, the burning rate must not exceed 3 inches/min for specimen thickness of 3 mm, and 1.5 inches/min for specimen thickness of more than 3 mm. In addition, the specimen is self-extinguishing.

V2 – in the vertical flammability test, the specimen must self-extinguish after an average duration of 25 seconds. Drips of flaming particles from the specimen on the cotton pads placed below may inflame these. Afterglow of the specimen must not exceed 60 seconds.

V1 – in the vertical flammability test, the specimen must self-extinguish after an average duration of 25 seconds (max. 30 seconds). Drips of flaming particles from the specimen on the cotton pads placed below must not inflame these. Afterglow of the specimen must not exceed 30 seconds.

V0 – in the vertical flammability test, the specimen must self-extinguish after an average duration of less than 5 seconds (max. 10 seconds). Drips of flaming particles from the specimen on the cotton pads placed below must not inflame these. Afterglow of the specimen must not exceed 30 seconds.