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UL 94

Posted on May 9, 2024 by
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What is UL 94?

"UL" is an abbreviation for UL Solutions, the American product safety company, or the certification certificates issued by the company. UL Solutions is one of the three organizations that make up UL Enterprises, formerly known as Underwriters Laboratories Inc. or Underwriters Laboratories Limited Liability Company (UL LLC). UL Solutions provides certification for materials, components, equipment, tools, and end products, as well as original standards and assessment methods based on the functionality and safety of each product. There are various UL standards including Sustainability Standards (UL 106, UL 110), Life Safety Standards (UL 217, UL 268), Standards for Building Products (UL 10A, UL 20), etc.

UL 94, the Standard for Safety of Flammability of Plastic Materials for Parts in Devices and Appliances testing, is a plastics flammability standard released by Underwriters Laboratories of the United States. The standard determines the material's tendency to either extinguish or spread the flame once the specimen has been ignited.

The VW-1 (vertical wire burn) rating is sometimes erroneously associated with UL 94, but it (and some other flammability tests) is described by UL 1581 (Reference Standard for Electrical Wires, Cables, and Flexible Cords).

Classifications of UL 94

From lowest (Least flame-retardant) to highest (Most flame-retardant):

  • HB: slow burning on a horizontal specimen; burning rate < 76 mm/min for thickness < 3 mm or burning stops before 100 mm.

  • V-2: burning stops within 30 seconds on a vertical specimen; drips of flaming particles are allowed.

  • V-1: burning stops within 30 seconds on a vertical specimen; drips of particles allowed as long as they are not inflamed.

  • V-0: burning stops within 10 seconds on a vertical specimen; drips of particles allowed as long as they are not inflamed.

  • 5VB: burning stops within 60 seconds on a vertical specimen; no drips allowed; plaque specimens may develop a hole.

  • 5VA: burning stops within 60 seconds on a vertical specimen; no drips allowed; plaque specimens may not develop a hole.

These levels describe the flammability performance of different plastic materials, ranging from the lowest HB level to the highest 5VA level. The higher the level, the better the flame retardancy of the material, and the quicker the cessation of burning, with no occurrence of particle dripping or formation of holes.

The Application Areas of UL 94

  • 1. Electronics and Electrical Equipment: UL 94 is widely used for evaluating the flammability performance of plastic components used in electronic and electrical devices. These components include enclosures, sockets, switches, wire insulation, and more. UL 94 testing helps determine the burning characteristics of plastic materials to ensure the safety of devices in the event of fire or exposure to heat sources.

  • 2. Automotive Industry: UL 94 is also extensively applied in the automotive sector. Plastic materials are used for manufacturing interior components, exterior parts, engine covers, wire harnesses, and more. UL 94 testing assesses the flammability performance of these materials, ensuring the safety and reliability of vehicles in case of fire incidents.

  • 3. Household Appliances: Plastic materials in household appliances also undergo UL 94 testing. Examples include TV casing, washing machine control panels, refrigerator interior components, and others. UL 94 testing evaluates the burning behavior of these materials to ensure their safety during normal use and in the event of accidents.

  • 4. Communication Equipment: Plastic materials play a significant role in communication devices, such as phone casings, wireless router housings, fiber optic adapters/panels/cassettes, and more. UL 94 testing is employed to assess the flammability performance of these materials, ensuring that the devices do not pose a fire hazard or contribute to fire spread during operation.

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