UL 94 is a flame resistance standard established by Underwriters Laboratories (UL) to evaluate the flammability of plastic materials used in various applications. To achieve a UL 94 rating, a material must meet certain requirements and undergo specific testing procedures. Below are the general requirements for a material to achieve a UL 94 rating:
1. Specified Thickness: The material should have a specified thickness, typically ranging from 0.0625 inches (1.6 mm) to 0.25 inches (6.4 mm), depending on the rating level.
2. Sample Preparation: Samples for testing should be prepared according to the required dimensions and shapes specified by UL 94.
3. Flame Exposure: The material is subjected to a controlled flame ignition source for a specific time period. There are different test methods under UL 94, such as the Vertical Burn (VB) test, Horizontal Burn (HB) test, and others, each with its own set of criteria.
4. Flame Propagation: The material's ability to resist the spread of flames is evaluated during the testing. The flame should not continue to propagate along the specimen after the ignition source is removed.
5. Dripping and Burning: The material's tendency to drip flaming particles and its self-extinguishing properties are observed during the test. For example, materials that pass the UL 94 V-0 rating should not drip flaming particles for more than 30 seconds.
6. After-Flame and Afterglow Time: The material's ability to resist after-flame and afterglow is measured. After the ignition source is removed, the material should not continue to burn or emit glowing particles for an excessive duration.
7. Remnant Burning: Certain UL 94 ratings also assess the material's resistance to remnant burning. The material is evaluated to ensure that any combustion remnants do not continuously burn or spread flames.
It's important to note that the specific requirements and criteria for achieving a UL 94 rating may vary depending on the desired rating level (e.g., V-0, V-1, V-2). Additionally, UL 94 evaluates materials under different orientations, such as vertical, horizontal, and inclined. It is recommended to refer to the UL 94 standard and consult with testing laboratories for the most accurate and up-to-date requirements for achieving the desired UL 94 rating.