UL is the abbreviation for the Underwriters Laboratories, this is an independent organisation in the United States to control and certificate product safety. UL provide safety related certification, validation, inspection and testing services to a range of clients including manufacturers, retailers, policy makers and regulators.
Contained within their extensive list of testing and product standards, the UL also specified the flammability test for UL94 for plastic materials. UL94 is a material burning test done on a defined specimen of raw material of the product in question. It does not, however, carry out a flame test on the final product.
UL94 differs between a horizontal burning test UL94 HB and a vertical burning test UL94 V.
For the vertical test UL94 V, there are three flame ratings defined: UL94 V0, UL94 V1 and UL94 V2.
UL94 HB – Horizontal Burning Test
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Test Criteria: | Burning rate of specimen in mm/min. |
| Classification: | According to HB |
UL94 V – Vertical Burning Test
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Test Criteria: | Afterflame time of specimen. Drip of flaming particles. |
| Classification: | According to V0, V1 or V2 |
In all these burning tests, an open flame is applied for a specified time to the specimen. As the burning behaviour also depends on the thickness of the material, it is important to classify the material not only according to HB, V0, V1 or V2 but also to mention the thickness of the specimen.
The following table is a summary of test procedures and requirements of the above four UL94 classifications:
| Horizontal Test UL94 | Vertical Test UL94 | ||||
| Classification | HB | V0 | V1 | V2 | |
| Number of specimen | 3 | 3 | 5 | 5 | 5 |
| Thickness of specimen | < 3mm | 3 to 13mm | up to max. 13mm | ||
| 1st flame application | 30 sec. | 30 sec. | 10 sec. | 10 sec. | 10 sec. |
| 2nd flame application | – | – | 10 sec. | 10 sec. | 10 sec. |
| Burning rate | max. 75 mm/min | max. 40 mm/min | – | – | – |
| Afterflame time after 1st flame application for each individual specimen | – | – | max. 10 sec. | max. 30 sec. | max. 30 sec. |
| Afterflame time after 2nd flame application for each individual specimen | – | – | max. 30 sec. | max. 60 sec. | max. 60 sec. |
| Total afterflame time for all 5 specimen after 1st and 2nd flame application | – | – | max. 50 sec. | max. 250 sec. | max. 250 sec. |
| Afterflame or afterglow of any specimen up to its end allowed | yes | yes | no | no | no |
| Cotton indicator ignited by flaming particles or drops allowed | – | – | no | no | yes |
Looking at the vertical test (V0, V1, and V2) results, it is evident from the above table that a material that complies with the UL94 V0 rating is considerably more flame resistant than products meeting the UL94 V2. When tested, materials that meet V2 ignited the cotton cloth via flaming particles or drops, meaning the product may not be suitable for areas where there is flameable material near by.
It is important to be aware that just because a material is UL94 tested and compliant, there can be a considerable difference in fire performance and safety between two materials, especially between UL94 V2 and UL94 V0.
ETS Cable Components current stock a range of UL94 rated electrical products, including:
– Single Bolt Nylon Cable Cleats – Including LUL approved version
– Two Bolt Nylon Cable Cleats – Including LUL approved version
– Red HV Cable Cleats
– Flexicon Trackside and Rail Vehicle Interior Flexible Conduit
– 3M Scotch 77 Tape
– Powersafe Connectors
For more information on our range of UL94 rated products, please contact our Sales Team.
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