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UL (Underwriters Laboratories), founded in 1894, is a global safety certification organization with over a century of history. Its standards are widely recognized, especially in the US market, and many retailers and buyers consider UL certification a prerequisite for product market access. UL certification indicates that a product has reached a certain level of safety, performance, and quality, effectively protecting consumers' lives and property.
Overview of UL 94 Flame Retardant Rating
UL 94 is a flammability testing standard for plastic materials established by Underwriters Laboratories (UL). It is a widely used global standard for evaluating the flammability of plastics. This standard evaluates a material's ability to extinguish itself after being ignited, based on factors such as burning rate, burning time, drip resistance, and whether the drips burn.
UL94 Flame Retardancy Rating Classification
UL94 is divided into 12 ratings, arranged from lowest to highest flame retardancy.
| Rating | Type | Description |
| HB | Horizontal Burning | Lowest flame retardancy rating, suitable for materials with low flame retardancy requirements |
| V-2 | Vertical Burning | Allows dripping molten material |
| V-1 | Vertical Burning | Allows dripping molten material, but self-extinguishing time is longer than V-0 |
| V-0 | Vertical Burning | Common highest rating, no dripping molten material allowed |
| 5VB | 5V Burning | Allows the test piece to be penetrated by the flame |
| 5VA | 5V Burning | Highest rating, no penetration allowed |
| VTM-0/VTM-1/VTM-2 | Film Materials | Suitable for plastic films |
| HBF/HF1/HF2 | Foamed Materials | Applicable to foamed materials |
Rating Criteria for Each Grade
HB Grade (Horizontal Combustion)
Sample thickness requirement: 1.5mm to 13mm; Combustion rate: less than or equal to 40mm/min or 75mm/min; Combustion ceases before the 100mm mark.
V-0 (Vertical Burning): After 10 seconds of flame combustion, the test piece must not ignite for more than 10 seconds; total burning time must not exceed 50 seconds; no dripping is allowed.
V-1 (Vertical Burning): Self-extinguishing time requirement is longer than V-0; dripping is allowed.
V-2 (Vertical Burning): Dripping of burning material is allowed; flame retardant requirements are lower than V-1.
5VA/5VB (5V Burning): After 5 seconds of flame combustion, the test piece must not ignite for more than 60 seconds.
5VA: The test piece must not be penetrated by the flame.
5VB: The test piece is allowed to be penetrated by the flame.
Test Methods
UL94 includes several test configurations:
Horizontal Burning Test (HB) - The most basic test
Vertical Burning Test (V-0/V-1/V-2) - The most commonly used
5V Test (5VA/5VB) - A more stringent test
Thin Film Test (VTM-0/VTM-1/VTM-2) - Applicable to thin film materials
Foamed Material Test (HBF/HF1/HF2) - Applicable to foamed materials
Application Areas
UL94 test results are commonly used in the following industries:
Electronics and Electrical Appliances
Automotive
Construction
Energy Storage
Important Notes
A higher UL94 rating indicates stronger flame retardancy, but a higher rating is not always better. The UL94 rating should be selected based on the material's application scenario and performance requirements, and testing should be conducted at different thicknesses to ensure product safety under various conditions. This standard does not apply to building and decorative materials.
