The flame-retardant ratings of plastics range from HB all the way up to 5VA, according to the UL94 standards. These levels indicate how well a material resists catching fire and sustaining combustion. Let’s break them down:
HB (Horizontal Burning): This is the lowest rating in the UL94 system. Materials with this rating must have a burn rate of less than 40 mm per minute when tested on specimens 3 to 13 mm thick. If the specimen is thinner than 3 mm, the burn rate should be under 70 mm per minute. Additionally, the test sample must self-extinguish before reaching the 100 mm mark.
V-2: In this category, the sample undergoes two 10-second burns. After each burn, the afterglow and afterfire must stop within 60 seconds. However, during testing, the molten drips may ignite a piece of cotton placed below.
V-1: Similar to V-2, the sample undergoes two 10-second burns. The afterglow and afterfire must extinguish within 60 seconds. Unlike V-2, the drips cannot ignite the cotton.
V-0: For this highest standard, the sample also goes through two 10-second burns. The afterglow and afterfire must cease within just 30 seconds, and the drips cannot ignite cotton either.
5VB: With this rating, the sample is subjected to five 5-second burns. The afterglow and afterfire must extinguish within 60 seconds, and the drips cannot ignite cotton. However, for large samples, it’s acceptable if they burn through entirely.
5VA: This is the top tier. After five 5-second burns, the afterglow and afterfire must stop within 30 seconds. Drips cannot ignite cotton, and even for large samples, the material must not burn through completely.
For further information about these ratings and their applications, feel free to explore the official site of **Ningbo Super Electronics Co., Ltd.**
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