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Regarding UL

UL Standards

It was formulated by the American company UL LLC (Underwriters Laboratories Limited Liability Company, hereinafter referred to as UL), which is the oldest safety standards development organization in the United States. Although it is a voluntary certification system, countries and companies that manufacture and sell raw materials and products exported to the United States also require UL approval, used worldwide.

UL-94 Standards

This standard specifies methods for evaluating the flame resistance (combustibility) of plastic materials used in parts of equipment and appliances.
※The standard specifies that polymeric materials used in the construction, finishes, wall and floor coverings, furniture and decorative items and other contents of buildings, materials with a thickness exceeding 13.0 mm, or materials with a surface area exceeding 1 m2 are not included.

UL-94 has two standards: HB and V (V-0, V-1, V-2).
These ratings are established in small scale testing using samples approximately 5 x 1/2 inch ignited with a 3/4 inch, 50 watt burner flame.
HB flame resistance (combustibility) evaluation is performed by applying a test flame to the edge of a horizontally placed sample and slowly burning the entire sample.
HB grade indicates that the material has been determined to burn at a rate less than the maximum specified.

V rating (e.g., V-2, V-1, V-0) is determined by checking that a test sample, placed vertically with the test flame striking the bottom of the sample, self-extinguishes within a specified time after the ignition source is removed and does not burn through to the top clamp or drip molten material that ignites a cotton indicator beneath the test specimen.
(5VA and 5VB classification tests involve the application of a test flame up to five times and measure the ability of an ignited material to extinguish or spread the flame.)

UL-94 Flame Retardant

Based on the results of flammability tests, materials are assigned one of 12 UL94 designated flammability classifications. These classifications, listed in descending order in three groups, are used to differentiate the flammability characteristics of materials after specimens are exposed to a test flame:

  • 5VA、 5VB、 V-0、 V-1、 V-2、 HB

    • 　This concerns materials commonly used in the manufacture of housings, structural parts and insulation for household appliances.
  • HF-1、HF-2、HBF

    • 　It concerns a low-density foam material often used in the manufacture of speaker grilles and soundproofing materials.
  • VTM-0、VTM-1、VTM-2

    • 　It is generally assigned to thin films that cannot be supported horizontally, usually flexible printed circuit boards.