Question #1:What is UL94 all about?
A UL flammability rating is nowadays highly regarded as evidence for the suitability of a polymer or compound for a proposed application. UL94 V-0, V-1 and V-2 are probably the most widely cited ratings as evidence of the behavior of a plastics material in fire conditions. Each of these tests require the examination of the material in the form of 5 x 12.5 mm. strips in each of three different thicknesses. A total of ten samples are tested in two sets at each thickness, each set previously conditioned under different environments. In the test, a specimen is mounted with its bottom end above a Bunsen burner, and burned at the bottom edge for 10 seconds. If burning ceases within 30 seconds, the flame is reapplied for a further 10 seconds. If the specimen drips particles, these are allowed to fall onto a layer of untreated surgical cotton placed below the specimen. Various criteria discriminate between V-0, V-1,or V-2, e.g., do the dripping particles ignite the cotton as they drip on it?
You can visit the UL website at UL WEBSITE. Or, keep on reading further (Questions #2 and beyond), for specific details of each requirement.
Criteria HB V-2 V-1 V-0
Number of bar specimens as received
3 5 5 5
Number of ignitions
1 2 2 2
Maximum flaming time per specimen per flame application, sec 30 30 10
Maximum total flaming time, 5 specimens, 2 ignitions, sec 250 250 50
Specimen drips, ignites cotton
Yes No No
Maximum afterglow time, per specimen, sec
60 60 30
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