The UL94 "Tests for Flammability of Plastic Materials for Parts in Devices and Applications" (Tests for Flammability of Plastic Materials for Parts in Devices and applications) of Underwriters Laboratories ( UL) describes a method for assessing and classifying the flammability of plastic materials. It was 22.2 adopted the same content in the standards IEC / DIN EN 60695-11-10 and -20 and the Canadian CSA C.
For the classification of specimens of the dimensions are 125 x 13 x S ( mm) ³ produced. The thickness S must correspond to the smallest wall thickness in the intended application and meet must not exceed 13 mm. Frequently in one or more of the halftone steps 0.40mm, 0.75 mm, 1.5 mm and 3.0 mm was tested.
The samples are then tested at the expense of the respective material suppliers by Underwriters Laboratories or in an accredited laboratory. The achieved classification is entered in public so-called Yellow Cards. On these, users can check whether a particular material of the required fire rating equivalent.
The tests are carried out with an open flame ( Bunsen burner ). The ignition source has according to the desired classification on a power of 50 watts ( 20 mm high flame) or 500 watts. It acts in the HB- test for 30 seconds or until the start flag, in the V test twice for 10 s and with the 5V test five times 5 s. On and subsequently removed again specimen Here, the burning time and the V- tests and the flakes of burning parts with the help of a cotton pad, which is located below the specimen evaluated.
The classification is made for the thickness tested in the levels of HB ( horizontal burning test ) and V- 0, V - 1, V- 2, 5 VA and 5VB ( vertical burning test ). These are - according to the height of the request - in detail for:
- HB: slow burning a horizontally clamped sample ( self-extinguishing or thickness <3 mm; rate < 75 mm / min ( HB75 ) in thickness 3 ... 13 mm; rate < 40 mm / min ( HB40 ) ).
- V -2: extinction of a vertically clamped test within 30 seconds.
- V -1: as V- 2, but no flaming drops of molten plastic allowed.
- V-0: such as V- 1, but the flame is extinguished in 10 seconds.
Plastics that meet at least Class V -2 can additionally be tested with the 500 -watt flame ( 125 mm flame height):
- 5VB: extinction of a vertically clamped specimen after five flame applications for each five seconds; no dripping permitted.
- 5va: how 5VB, additional test on a horizontally clamped plate; neither dripping nor the formation of burn holes with a diameter> 1 mm are allowed.
Have similar classifications for foams ( HF-1, HF -2, HBF) and thin films ( VTM -0, VTM -1, VTM -2).