March 1, 2019

UL 94 Classification and Flame-Retardant Thermoplastics

By Protolabs

What is UL 94?

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
HB Slow burning on a horizontal part
V-2 Burning stops within 30 seconds on a part allowing for drops of vertical flammable plastic.
V-1 Burning stops within 30 seconds on a vertical part allowing for drops of plastic that are not inflames.
V-0 Burning stops within 10 seconds on a vertical part allowing for drops of plastic that are not inflames.
5VB Burning stops within 60 seconds on a vertical part not allowing for drops of plastic that are not inflames. Test specimens may have a burn-through (a hole may be present). 
5VA Burning stops within 60 seconds on a vertical part not allowing for drops of plastic that are not inflames. Test specimens may not have a burn-through (no hole).

Effects of Flammability
Colorant/Additives: For best results, stick with a base resin with no additives as most additives may not carry a UL rating. 

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.

Thickness Nominal Value Unit Test Method
Flame Rating: UL   UL 94
0.0295 in. V-2  
0.0591 in. V-0  
0.0787in. 5VB  

V-0-Rated Injection Molding Materials
Protolabs offers select materials that have a UL 94 V-0 rating for injection molding 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. Additionally, our Carbon DLS 3D printing technology provides a flame retardant option: Carbon EPX. This material is flame retardant UL94 V-0 at 2mm thick.

Carbon EPX 86FR is a flame-retardant resin that offers functional toughness, high strength, and long-term stability. It works well in a variety of applications that require UL 94 V-0 or FAR 25.853(a) ratings.  

Primary Benefits 

  • Flame retardant (UL94 V-0 at 2 mm thick)
  • Chemical resistance  

 

Stocked materials with UL 94 V-0 or greater
ABS Polylac PA-765
ABS/PC  Bayblend FR110, Bayblend FR 3010, Cycoloy C2950 and Cycoloy C6600
LCP Vectra E130i (30% glass fiber)
PA RTP 203 FR (20% glass nylon)
PBT Valox 420SEO (30% glass fiber)
PC

Lexan 940 and Lexan 3412R (20% glass fiber)

PEEK

Victrix 450G

PP

Maxxam FR PP 301

PPS

Ryton R-4 (40% glass fiber)

PPSU

Radel R-5000 NT

TPE

Santoprene 251


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 877.479.3680 or [email protected].

For more information on thermoplastic material properties in general, read our free white paper: Injection Molding Material Selection Guide.

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