The UL 94 Vertical (UL 94V) Flammability Test was developed by Underwriters Laboratories to evaluate the physical characteristics and safety of different plastics when they’re exposed to flame. During the course of a UL 94V test, the material under evaluation is tested in two different states: first, in its unaltered “as manufactured” state, and then in its “aged” state, a condition that is achieved by exposing the plastic sample to a temperature of 158°F for a full 7 days.
The Steps of the UL94V Burn Test
- Before the test begins, plastic samples are placed vertically in the burn chamber. Each sample is 127mm x 12.7mm in dimension, with the same thickness as the final product that will be formed from the plastic.
- Once the sample has been mounted, a carefully controlled flame is placed under the specimen for 10 seconds and then removed. When the flame is no longer in contact with the specimen, any residual flaming combustion of the plastic sample is observed and recorded.
- When the plastic sample finally self-extinguishes, the controlled flame is immediately reapplied for another 10 seconds, and then removed. Again, the specimen’s flaming combustion (in the absence of flame exposure) is recorded.
- Lastly, a piece of dry surgical cotton is placed 12 inches below the combusting sample. If any drips fall onto the cotton and cause it to ignite, this detail is also recorded.
When all of the flame test data has been gathered, it’s used to group the tested material into one of three specific material classes: 94V-0, 94V-1, or 94V-2. Below you’ll find the requirements for each classification.
- Following either or both of the controlled flame applications, samples may not sustain burning combustion for longer than 10 seconds.
- Total flaming combustion time for 5 samples (counting both controlled-flame applications) may not exceed 50 seconds.
- None of the samples may be burned up to the mounting clamp by either flaming or glowing combustion.
- None of the samples may drip flaming particles that result in the ignition of the surgical cotton below them.
- Following the removal of the second controlled flame, samples may not exhibit glowing combustion for more than 30 seconds.
- Following either controlled flame application, none of the samples may sustain flaming combustion for longer than 30 seconds.
- The total flaming combustion time for 5 samples (each exposed twice to a controlled flame) may not exceed 250 seconds.
- Flaming or glowing combustion may not result in any of the samples being burned up to their holding clamps.
- While samples may drip flaming particles that burn briefly, these particles may not cause the actual ignition of the underlying dry surgical cotton.
- Samples may not exhibit glowing combustion for more than 60 seconds after the removal of the second controlled flame.
- Following either the first or second controlled-flame application, none of the samples may support flaming combustion for longer than 30 seconds.
- The total flaming combustion time for 5 samples (each being twice-exposed to a controlled flame) may not exceed 250 seconds.
- Flaming or glowing combustion may not cause any of the samples to burn up to their holding clamps.
- Samples are allowed to drip briefly-burning flaming particles, which may cause the dry surgical cotton they land on to ignite.
- Upon the removal of the second controlled flame, none of the samples may exhibit glowing combustion for a period of time greater than 60 seconds.
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