A polycarbonate UL94 rating answers a narrower question than the drawing usually assumes. An appliance manufacturer specified V-0 polycarbonate for a control enclosure, received sheet marked HB, and discovered the difference only when the certification body asked for the test report. The sheet was polycarbonate. The rating was not the one on the drawing.
The polycarbonate flame retardant rating UL94 is one of the most quoted and least understood lines on a data sheet. It is a small-scale laboratory test, and it says something specific.
What a polycarbonate UL94 rating measures
UL94 rates how a plastic specimen burns in a controlled horizontal or vertical test. HB is the horizontal test, the weakest rating. V-2, V-1 and V-0 are vertical tests, with V-0 the most demanding: the specimen must self-extinguish quickly and must not drip flaming material that ignites the cotton below.
It is not a building fire classification, not a smoke toxicity rating and not a proxy for what happens to a one metre panel in a real fire. Those questions belong to other standards.
Thickness is part of the rating, not a footnote
A UL94 result is always tied to a specimen thickness. A material rated V-0 at 3 mm may be V-2 at 1.5 mm, because thinner sections have less material to absorb heat and lose heat faster.
When a drawing says V-0, it should say V-0 at what thickness. A sheet supplied at 2 mm against a V-0 rating established at 3 mm is not compliant, even though the data sheet is genuine.
- HB: horizontal burn, slow spread, acceptable for non-critical housings.
- V-2: vertical, self-extinguishing, flaming drips permitted.
- V-1: vertical, self-extinguishing, no flaming drips, longer burn permitted than V-0.
- V-0: vertical, self-extinguishing within 10 seconds, no flaming drips.
What changes the result in real polycarbonate
Standard clear polycarbonate typically achieves V-2 at common thicknesses and can reach V-0 with flame retardant additives or specific grades. Additives affect colour, clarity and UV stability, which is why a V-0 grade is rarely as optically clear as a general purpose sheet.
Coatings are a separate matter. A hard coat for abrasion resistance does not change the UL94 rating of the substrate, and a supplier who claims it does should be asked for the test report.
What to request instead of a claim
Ask for the UL yellow card reference, the grade designation, the thicknesses covered and the test laboratory. A yellow card is a public record and can be checked independently; a data sheet line cannot.
For an enclosure that must meet a final product standard, ask the sheet supplier for the rating at the thickness you will actually mould or machine, and confirm with the certification body before production, not after.
Where the application also needs ballistic or impact performance, the flame rating is only one of several requirements; our guide to flame retardant acrylic and PC sheet under UL94 compares the two materials.
Common specification errors
The three recurring errors are quoting V-0 without a thickness, assuming a clear grade is automatically V-0, and applying a building fire class expectation to a UL94 rating. Each one surfaces at the certification stage, which is the most expensive place to fix it.
River People supplies flame retardant polycarbonate with the yellow card reference, the rated thicknesses and the colour options stated on the quotation.
Send the enclosure drawing, the wall thickness and the standard the final product must meet to oversales@rpplexiglass.com and we will confirm which polycarbonate flame retardant rating UL94 grade and thickness fits.
Frequently Asked Questions
What is the difference between V-0 and V-2 in polycarbonate?
Both are vertical burn tests. V-0 requires self-extinction within about 10 seconds with no flaming drips; V-2 allows flaming drips that may ignite cotton. V-0 is the stricter rating and usually needs a flame retardant grade.
Is clear polycarbonate V-0 rated?
Standard clear PC is often V-2 at common thicknesses. V-0 grades exist but the additives can reduce clarity and shift colour, so the grade and thickness must be confirmed on the yellow card.
Does UL94 make polycarbonate fireproof?
No. UL94 is a small-scale specimen test. It does not describe panel behaviour in a real fire, smoke toxicity or building fire class, which are covered by separate standards.