TIPS WITH TONY: Flame-Retardant Thermoplastics and UL Classifications

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 vertical                                             part allowing for drops of 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 with no drops of plastic allowed but may                                               burn through the part.

5VA

                                          Burning stops within 60 seconds on a vertical                                             part with no drops of plastic allowed and                                                     cannot burn through the part.

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. 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 color 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.

Thickness

Nominal Value Unit

Test Method

Flame Rating: UL  

UL 94

0.0295 in.

V-2

 
0.0591 in.

V-0

 
0.0787 in.

5VB

V-0-Rated Injection Molding Materials
Proto Labs 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.

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 customerservice@protolabs.com.

For more information on thermoplastic material properties in general, read our free white paper: Materials Matter: The Material Selection Process.

This entry was posted in Tips with Tony and tagged , , , by Tony Holtz. Bookmark the permalink.

About Tony Holtz

Tony is a technical specialist at Proto Labs with more than 10 years of experience ranging from CNC mill operator to mold designer to customer service engineer. While his formal education is in industrial machinery operations, he has extensive knowledge and experience in both traditional and advanced manufacturing processes and materials. Throughout his tenure at Proto Labs, Tony has worked with countless designers, engineers and product developers to improve the manufacturability of their parts.

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