UL 94 Classification and Flame-Retardant Thermoplastics
UL 94 is a plastics flammability standard released by the Underwriters Laboratories (USA). The standard classifies plastics according to how they burn in various orientations and part thicknesses from the lowest flame-retardant to most flame-retardant in six different classifications.
|UL 94 Rating
|Definition of Rating
|Slow burning on a horizontal part
|Burning stops within 30 seconds on a part allowing for drops of vertical flammable plastic.
|Burning stops within 30 seconds on a vertical part allowing for drops of plastic that are not inflames.
|Burning stops within 10 seconds on a vertical part allowing for drops of plastic that are not inflames.
|Burning stops within 60 seconds on a vertical specimen; no drips allowed; plaque specimens may develop a hole.
|Burning stops within 60 seconds on a vertical specimen; no drips allowed; plaque specimens may not develop a hole.
Effects of Flammability
Colourant/Additives: For best results, stick with a base resin with no additives as most additives may not carry a UL rating. If a specific additive is required, you would likely need to work with a compounder that could custom create a flame-retardant blend of the base resin, like colour matching, for example.
Part Thickness: UL ratings are measured at various thicknesses and this can drastically change your part’s UL rating. If you were looking for a UL 94 V-0 material for a part with thin or thick walls, as shown in the chart below, your part may fail — so pay close attention to wall thickness and material selection.
|Nominal Value Unit
|Flame Rating: UL
V-0-Rated Injection Moulding Materials
Protolabs offers select materials that have a UL 94 V-0 rating for injection moulding and can always run custom materials with approval. These would likely need to be customer-supplied resins as the demand may not be large enough to be added as a stocked resin.
|Stocked materials with UL 94 V-0 or greater
|Technyl A 20 V25 25% Glass Fibre, Latamid 66 H2 G/25-V0KB1 25% Glass Fibre
|CCP 4115 104F 15% Glass Fibre
Lexan 3412R 20% GF, Lexan 3414R 40% GF
Fortron 1140L4 40% Glass Fibre
Material testing must be completed by UL in order to provide the proper “yellow card” as there are many other classifications available. If you have further questions on materials or whether parts meet UL classifications, please contact our customer service engineering team at +44 (0) 1952 683047 or [email protected]
For more information on thermoplastic material properties in general, read our free white paper: Materials Matter: The Material Selection Process.