Dear Joslyn:
I am designing an electrical cover for a customer. I need a material that won’t catch fire or burn a hole in my customer’s pocket. What do you suggest?
– Mr. Burns
Dear Mr. Burns:
All thermoform plastics are assigned a flammability standard by the Underwriters Laboratories (aka UL). These standards are based on how each thermoform plastic material burns in different orientations and thicknesses. In the UL flame rating chart below, we’ve listed the classifications, material options and a general idea of cost. We hope this helps you find the right flame-resistant plastic material!
| UL 94 Rating | Definition | Types of Material | Estimated Cost |
| HB |
Flame applied once to material in a horizontal position. Burn rate is< 40mm/min for materials 3-13mm thick or < 75mm/min for materials < 3mm thick. Flame is extinguished before the first mark. |
ABS HDPE HIPS LDPE PET TPO |
$ |
| V-1 | Material tested in a vertical position and is able to self-extinguish within 30 seconds. Test indicates if particles not on fire dripped onto cotton batting below. | ABS/PVC Blends | $$ |
| V-0 | Material tested in a vertical position and is able to self-extinguish within 10 seconds. Test indicates if particles not on fire dripped onto cotton batting below. | Acrylic Kydex |
$$ |
| 5VB | Material tested in a vertical position. Surface burn (up to five times). Material is able to self-extinguish within 60 seconds and does not drip flaming particles. Burn through (holes) permitted. |
Acrylic/PVC Blends |
$$$ |
| 5VA | Material tested in a vertical position. Surface burn (up to five times). Material is able to self-extinguish within 60 seconds and does not drip flaming particles. Burn through (holes) not permitted. *Highest UL flame rating |
ABS/PVC Blends Kydex T & V103 |
$$$ |
– Joslyn Manufacturing
Each thermoform plastic resin has characteristics that align better with certain applications more so than others. This UL flame rating chart will help you choose the material that will meet your needs.
Have a question for Dear Joslyn? Send your inquiry to bhardy@joslyn-mfg.com or use the hashtag #DearJoslyn.
