ENGINEERING TECH TIPS | 4 APRIL 2025
Understanding UL94 Flame Ratings
Tech Tips from Our Engineers at Bamberger Amco Polymers
What are the UL94 Flammability Tests?
The UL94 flammability tests offer a preliminary indication of a plastic material’s usability in certain devices or appliances.
These tests use standard specimens and are conducted under predefined conditions. They compare the relative burning characteristics of different materials, assessing any changes that may take place during use in their intended application.
A UL94 rating is not intended to reflect the hazards of a material under actual fire conditions.
5VA Surface Burn
This test involves applying a flame to a bar of test material for five seconds, five separate times. The test material must stop burning within 60 seconds and cannot develop a burn-through hole. Passing this test earns a material the highest, most flame-retardant UL94 rating.
5VB Surface Burn
This rating test involves applying a flame to a bar of test material for five seconds, five separate times. The test material must stop burning within 60 seconds, but it is allowed to develop a burn-through hole.
V-0 Vertical Burn
To pass this test, a material must stop burning within ten seconds after a flame is applied to it twice (for ten seconds each time). In addition, no flaming material drips can occur.
V-1Vertical Burn
To pass this test, a material must stop burning within 60 seconds after a flame is applied to it twice (for ten seconds each time). No flaming material drips can occur.
V-2 Vertical Burn
To pass this test, a material must stop burning within 60 seconds after a flame is applied to it twice (for ten seconds each time). Unlike V-0 and V-1 tests, flaming material drips are allowed.
HB Horizontal Burn
In this test, material must display a horizontal burn rate of less than 3" per minute — or stop burning altogether before 5” of the material test bar catch fire. HB-rated materials are considered “self-extinguishing.”
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