Layout of the Yellow Card
Approval of Engineering Plastics
UL approval is generally essential before equipment can be sold in the United States. Approval tests on equipment are lengthy and expensive. The operation can however be greatly simplified if UL-approved materials, i.e. appearing on the yellow cards, are used. Engineering plastics manufacturers are therefore having an increasing number of materials approved, to make things easier for users.
Approvals covers three aspects:
- flame class, governed by the UL 94 standard,
- temperature indices, governed by the UL 746 B standard,
- basic properties, determined under the UL 746 A standard.
The results are given for each material, in each colour, and for a specific thickness, which is the actual thickness of the specimen tested. This means that comparisons between materials are valid only if the thickness is the same.