One of the most commonly known standards for plastics is the UL 94 standard. These small scale tests are intended to serve as a preliminary indication of their acceptability with respect to flammability in a particular application. You may often find the UL 94 flammability tests related to other UL standards associated with plastics like UL 746 A and B which are used for short and long term property evaluations. Or UL 746 C which provides the test procedures for evaluating plastics used in electrical equipment.
The most common tests in UL 94 are the HB (horizontal burn) and the V-0, V-1 and V-2 (vertical burn) series.
HB
This horizontal burn test applies a flame for 30 seconds and has three classifications for passing:
a) Not having a burn rate exceeding 40mm (1.6 inches) per minute over a 75mm (3.0 inch) span for materials having a thickness between 3.0mm (0.118 inches) to 13mm (0.511 inches)
b) Not having a burn rate exceeding 75mm (3.0 inch) per minute over a 75mm (3.0 inch) span for materials having a thickness less than 3.0mm (0.118 inches).
c) Ceases to burn before the 100mm reference mark.
Note that materials burn slower in the horizontal, than they do in the vertical. All grades of polycarbonate should have no problem passing this test.
V-0, V-1 or V-2
The vertical burn test applies a flame for 10 seconds and then the after-flame is measured as time t1. As soon as the after-flame ceases, the flame is applied again for 10 seconds and the second after-flame time is measured as t2 and the after-glow is measured as time t3. A cotton indicator is placed under the specimen to catch any flaming particles from the sample. The table indicates the criteria for each of the classifications.
Most polycarbonates will require a flame inhibiting additive to achieve a V rating.
HighLine Polycarbonate can offer a clear polycarbonate that will have a V-0 rating at a thickness of 3mm or greater.
We can also offer an opaque polycarbonate that will have a V-0 rating at thickness at a thickness of 1.5mm or greater.
For additional information on UL standards, please contact Liz Grimes – Technical Director Tel: 215.872.3532 Email: LGrimes@highlinepc.com