UL Approval
Question:
As a designer of plastic parts for stereo and other electronics applications, I am often required to specify a resin or compound that is UL rated and approved. Can you tell me what the UL approval is for?
- Crazy Eddie
Answer:
Dear Crazy Eddie, UL approval of plastic materials comes in several forms. Basically, UL approval is your guarantee that the material you are purchasing has passed stringent flammability, electrical and mechanical tests conducted by Underwriters Laboratories, Inc. The type of UL approval you need depends solely on the type of part you are designing.
For instance, The Plastics Group issues yellow cards with some resin shipments that show compliance with the UL-94 HB flammability test. These cards tell you that The Plastics Group's talc, calcium carbonate, and glass-filled materials are UL approved for "portable, attended, intermittent-duty household use appliance enclosures (e.g., hair dryers) or for decorative parts."
What else does this tell you? Again, quoting directly from the UL test descriptions, "a material classed 94 HB shall:
- Not have a burning rate exceeding 40 mm per minute over a 75 mm span for specimens having a thickness of 3.0 - 13 mm, or:
- Not have a burning rate exceeding 75 mm per minute over a 75 mm span for specimens having a thickness less than 3.0 mm, or:
- Cease to burn before the 100 mm reference mark."
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