UL flame retardant standards

Comparison of UL94 plastic flame retardant rating and U1581L VW-1 flame retardant rating
There are 12 types in UL94: HB, V-0, V-1, V-2, 5VA, 5VB, VTM-0, VTM-1, VT
M-2, HBF, HF-1, HF-2.
Flammability UL94 rating is a widely used flammability performance standard for plastic materials. It is used to evaluate the ability of a material to extinguish after being ignited. There are many evaluation methods based on burning speed, burning time, anti-drip ability and whether the dripping beads burn. Many values can be obtained for each material being tested based on color or thickness. When selecting a material for a product, its UL rating should meet the thickness requirements for the wall portion of the plastic part. The UL rating should be reported along with the thickness value, only the UL
Grade without thickness is not
Enough.
Plastic flame retardant grades include HB, V-2, V-1, V-0, 5VB
Increasing step by step towards 5VA:
HB: Flame retardant rating of UL94 standard midsole. Requires that for samples 3 to 13 mm thick, the burning speed is less than 40
millimeters per minute; samples less than 3 mm thick,

The burning speed is less than 70 mm per minute; or it goes out before the 100 mm mark.

V-2: After two 10-second combustion tests on the sample, the afterflame & afterburning went out within 60 seconds. Dropping particles can ignite cotton.

V-1: After two 10-second combustion tests on the sample, the afterflame & afterburning went out within 60 seconds. Dropping particles must not ignite cotton.

V-0: After two 10-second combustion tests on the sample, the afterflame & afterburning are extinguished within 30 seconds. Dropping particles must not ignite cotton.

5VB: After five 5-second combustion tests on the sample, the afterflame & afterburn were at 60
It goes out within seconds. Dropping particles must not ignite cotton. Burn-through is allowed for bulk samples.

5VA: After five 5-second burning tests on the sample, the afterflame & afterburn is at 30
It goes out within seconds. Dropping particles must not ignite cotton. Burning of bulk samples is not allowed
Wear.
Wire burning methods in UL1581:
1. VW-1: Vertical burning test (UL wire burning grade)
2. FT1: vertical burning test;
3. FT2: Horizontal burning test;
4. FT4: vertical combustion test;
5. FT6: Horizontal burning and smoke test. (FT
The combustion rating of the class is the CSA standard wire burning rating)
Among the above levels: VW-1 and FT1 are the same level. FT2 is easy to pass and the level is low. (FT6>FT4>FT1>FT2);

VW-1 is stricter than FT1. Both are vertical combustion. Judgment criteria: 1.
The burning mark (kraft paper) cannot be charred more than 25%; 2.
5 15 second burns continued
The ignition time cannot exceed 60 seconds; 3. Burning drippings cannot ignite cotton; VW-1 requirements meet 1, 2, and 3;
FT1 only requires 1,2
For the wire industry:
UL 94 of V-2, V-1, V-0,
5VA and 5VB assess the materials used in the wires. During the test, standard samples must be prepared using additional test materials and will not be marked on the wires.

VW-1 VW-2 FT-1
FT-2 assesses the wire itself. After passing the test, the corresponding grade can be marked on the wire.

The flame retardancy of wires and the flame retardancy of UL94 are two completely different things. For example, an insulating material can pass the V-0 of UL94.
But it may not be able to pass VW-1;

In addition, UL94 is a flame retardant for insulating materials, while the flame retardant requirements for wires are generally UL758 62
1581 on; different objects;
So V-0 V-1
The flame retardancy in UL94 is not the flame retardancy of the wire at all; there is no “V-0” printed on the AWM wire!

VW-1/FT1 and UL94
There is a big difference in equipment for V0 combustion test:
1. The height and temperature of the flame are different
2. The methane flow rate used in the test is also different
3. The back pressure of methane is also different
4. The volume of the combustion box is also different: VW-1 requires more than 4 cubic meters, while V0
It only requires more than 0.5 cubes
5. The number of burnings is also different
6. In the combustion results: V0 requires recording the residual burning time, but VW-1 does not!

However, the test conditions and test methods of 5V class combustion and VW-1 combustion in UL94 are similar, relatively close!

Remind everyone: Whether it is VW-1 or UL94 combustion test equipment, you must refer to ASTM5025 and
ASTM5027,
UL1581 and UL94 are only test methods, and the requirements for test equipment must comply with ASTM standards!

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