Why did the same compound get V-0 and FH-2?

Answer: FH-2 maps to V-1, a step lower by definition. Conditioning covers the rest: 48 h instead of 24 h lifted afterflame from 8.4 s to 12.6 s, past the 10 s line.

Is V-0 exactly the same as FH-3?

Answer: The criteria match: 10 s single, 50 s across ten applications, 30 s afterflame plus glow, no cotton ignition. Only code and field order differ.

Why fix the specimen at 125 mm × 13 mm × 3 mm?

Answer: Both use that geometry and 3 mm matches common case walls. A 0.2 mm wall change moves afterflame by 2 s, so bars are cut along and across the flow.

Eight seconds each but 62 s in total, is that the top grade?

Answer: No. The single-value line passes, the 50 s total does not, and 62 s overshoots by 12 s, the rule most readers of case ul94 gb skip.

Does a passing material test cover the whole case?

Answer: No. Both standards judge bars, so latches, gaskets and liners need their own evidence, and acceptance files list material and case separately.

Case Ul94 Gb: UL94 vs GB/T 2408

Quick answer: Case ul94 gb results do not transfer: the same 3 mm PP compound reads V-0 on UL94 fields and only FH-2 on GB/T 2408 fields, a one-grade gap.

Two standards, one compound
How a 125 mm × 13 mm × 3 mm bar burns
Reading the seconds
FH-1 to FH-3 against V-2 to V-0
Fields for the report and the drawing
FAQ

1. Two standards, one compound

One batch of 3 mm polypropylene compound went to two labs, five bars each. Lab A reported V-0 under UL94: longest single afterflame 8.4 s, ten applications totalling 37.6 s. Lab B reported FH-2 under GB/T 2408: longest single afterflame 12.6 s, total 48.2 s. Same lot, one grade apart.

Three fields explain it: codes run in opposite directions, afterglow is booked differently, and the drip criterion sits on another grade.

Item	UL94	GB/T 2408	Changes the verdict
Grade codes	V-0, V-1, V-2, zero strictest	FH-3, FH-2, FH-1, three strictest	Yes, reversed
Specimen	125 mm × 13 mm × 3 mm	125 mm × 13 mm × 3 mm	No
Flame	20 mm blue, 10 s, twice	20 mm blue, 10 s, twice	No
Five bars, ten applications	≤50 s	≤50 s	No
Afterglow	Merged into the 30 s field	Its own seconds	Yes
Dripping ignites cotton	Allowed only at V-2	Allowed only at FH-1	Yes

Geometry and flame are one test across both standards. The 12.6 s was no sloppy work either, since GB/T 2408 bars condition 48 h at 23 ℃ against a common 24 h, and a day of drying lifts afterflame by about 4 s.

2. How a 125 mm × 13 mm × 3 mm bar burns

Both standards share one geometry: 125 mm long, 13 mm wide, 3 mm thick. That 3 mm matches most case walls, so the report line must agree with the drawing, and 0.2 mm of wall moves afterflame by 2 s.

Case ul94 gb test case standing open on a concrete bench, grey egg-crate foam in the lid, black foam dividers holding barcode-labelled cartons

Bars are cut from the side wall, one along the melt flow and one across it, and the cross-flow bar usually burns 1.5 s to 2.5 s longer.

The routine is fixed: burner at 45°, blue flame 20 mm, core on the lower 10 mm, applied 10 s, then t1 timed; the moment it stops, a second 10 s application gives t2 and the glow t3.

Cotton wool sits 300 mm below the bar, and a drip that sets it alight fails; both standards place that criterion identically. A copper block check comes first, flame set to 20 mm ± 1 mm, because a flame 3 mm long cuts afterflame by more than 1 s.

3. Reading the seconds

The top grade holds two lines at once: no single afterflame above 10 s, no more than 50 s across ten applications.

An 8.4 s result leaves 1.6 s of headroom, and one bar dragging to 11 s voids the grade. Both standards allow a retest, but the new data belongs beside the first round.

Grade	Single afterflame	Ten applications	Afterflame plus glow	Cotton ignition	Codes
Top	≤10 s	≤50 s	≤30 s	Not allowed	V-0 and FH-3
Middle	≤30 s	≤250 s	≤60 s	Not allowed	V-1 and FH-2
Low	≤30 s	≤250 s	≤60 s	Allowed	V-2 and FH-1

Middle and low differ in one column: whether a drip may ignite the cotton, that is, whether molten polymer falling off a burning case lights what it lands on.

Afterglow is the column people skip: the bar keeps glowing dull red after the flame dies and that time counts inside 30 s, with carbon black in a dark shell stretching glow 6 s to 9 s past a light colour.

4. FH-1 to FH-3 against V-2 to V-0

The mapping is one sentence: FH-3 equals V-0, FH-2 equals V-1, FH-1 equals V-2. Criteria match line by line; only the numbering reverses, one scale tightening as the digit falls, the other as it rises.

Case ul94 gb assembly workshop where two workers in short sleeves inspect black cases on orange stools, stacks of black shells and wrapped pallets

That reversal is the expensive misunderstanding. A tender asks for nothing below FH-2, a supplier answers with a V-0 report, and both sides believe it passes; FH-2 stops at V-1, so V-0 clears the bar by a grade.

Above the codes sits the method: GB/T 2408 and IEC 60695-11-10 share burner, bar and flame routine, while IEC prints the grades as V-0, V-1, V-2.

Write both codes into the technical agreement, for instance vertical burn not below FH-3 of GB/T 2408, equivalent to UL94 V-0. Reports also separate material from finished case, because latches, gaskets and liners burn on their own terms.

5. Fields for the report and the drawing

An acceptable report yields six fields: specimen thickness, worst single afterflame, ten-application total, afterglow seconds, cotton ignition and grade.

Field	UL94 wording	GB/T 2408 wording	What the case project takes
Specimen	3.0 mm, worst thickness attached	3.0 mm	Thinnest wall of the case
Single afterflame	Max of five bars	Max of five bars	Maximum, never the mean
Total afterflame	Sum of ten	Sum of ten	≤50 s
Afterglow	Inside the 30 s field	Separate seconds	Separate value ≤30 s
Drip	Yes or no, ignition noted	Yes or no	Write not ignited
Grade	V-0	FH-3	Both codes side by side

Watch the worst thickness line: a nominal 3 mm shell measures 2.82 mm in places and burns faster there, so shipping 2.8 mm goods against a 3.2 mm V-0 report usually retests into V-1. Mean afterflame is the easiest number to dress up, since four bars at 6 s and one at 22 s average 9.2 s yet the maximum drops a grade.

Conclusion

Run case ul94 gb acceptance field by field, not verdict by verdict. Start with the codes: FH-3 against V-0, FH-2 against V-1, FH-1 against V-2, reversed in direction, so both belong in the technical agreement. Then the seconds: worst single afterflame from five bars, 50 s across ten applications, 30 s once afterglow stands alone, and the drip marked as not igniting the cotton. Then the thickness, where 3.0 mm has to match the thinnest wall on the drawing, since 0.2 mm can cost a grade. Codes convert, seconds do not, and a verdict without fields counts as a fail.

This article discusses container-side specifications and design implications only, and does not cover any handling, loading or use of the contents.