Q: |
What do you need for a material to pass UL94? |
A: |
A UL flammability rating is nowadays highly regarded as evidence for the suitability of a polymer or compound for a proposed application. US compounder RTP has published a guide to the tests and procedures involved in obtaining UL listings. UL94 V-0, V-1 and V-2, probably the most widely cited ratings as evidence of the behavior of a plastics material in fire conditions, require the examination of the material in the form of 5 x 12.5 mm. strips in three thickness. A total of ten samples are tested in two sets at each thickness, one set after conditioning for 48 hours at 73°F(23°C); and 50 percent RH, and the other after similar conditioning for 7 days at 158°F(70°C). In the test, a specimen is mounted with its bottom end above a Bunsen burner tube, and a blue high flame is applied to the centre of the lower 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 12 in.(30 cm.) below the specimen. |
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