The UL test methods are aligned with IEC 60707, IEC 60695-11-10, IEC 60695-11-20, ISO 9772 and ISO 9773 standards used to determine fire properties.
UL Classifications Majorly Used for Plastics
(Source: W. L. Gore & Associates, Inc.)
Vertical Burning Test for Classifying Materials
UL 94 V Rating: V-0, V-1, V-2
This test measures the self-extinguishing time of the vertically oriented polymer specimen. The top of the test specimen is clamped to a stand and the burner is placed directly below the specimen. The test evaluates both the burning and afterglow times and dripping of the burning test specimen.
The material will be rated:
- V-0: if flame extinguishes within 10 seconds with no dripping
- V1: if flame extinguishes within 30 seconds with no dripping
- V2: if flame extinguishes within 10 seconds with dripping
Flammability rating UL 94 V
| Test Criteria | V-0 | V-1 | V-2 |
|---|---|---|---|
| Burning time of each individual test specimen (s) (after first and second flame applications) | ≤10 | ≤30 | ≤30 |
| Total burning time (s) (10 flame applications) | ≤50 | ≤250 | ≤250 |
| Burning and afterglow times after second flame application (s) | ≤30 | ≤60 | ≤60 |
| Dripping of burning specimens (ignition of cotton batting) | no | no | yes |
| Combustion up to holding clamp (specimens completely burned) | no | no | no |
(Source: UL LLC)
UL 94 VTM Rating: VTM-0, VTM-1 and VTM-2 – Thin Material Vertical Burning Testing
This test method is used for thin specimen or materials that are too flexible or may distort, shrink or flex during the traditional vertical testing (failure to pass the UL 94 V test is a precondition of all VTM ratings). This test is similar to the vertical burning test except that the material is wrapped around a mandrel before clamping to the stand and the flame application is reduced. In this test, the flame is applied only for 3 seconds.
Flammability rating UL 94 VTM
| Test Criteria | VTM-0 | VTM-1 | VTM-2 |
|---|---|---|---|
| Burning time of each individual test specimen (s) (after first and second flame applications) | ≤10 | ≤30 | ≤30 |
| Total burning time (s) (10 flame applications) | ≤50 | ≤250 | ≤250 |
| Burning and afterglow times after second flame application (s) | ≤30 | ≤60 | ≤60 |
| Dripping of burning specimens (ignition of cotton batting) | no | no | yes |
| Combustion up to holding clamp (specimens completely burned) | no | no | no |
(Source: UL LLC)
UL 94 5V Rating: 5V, 5VA, 5VB – Vertical Testing is done on both bar and plaque specimens
For any material to achieve a 5v classification, the test specimens must not burn with flaming and/or glowing combustion for more than 60 seconds after the fifth flame. Also, the test specimens must not drip.
Flammability rating UL 94
| Test Criteria | 5VA | 5VB |
|---|---|---|
| Burning and afterglow times of specimens after fifth flame application (s) | ≤60 | ≤60 |
| Dripping of burning specimens | no | no |
| Hole formation | no | yes |
(Source: UL LLC)
Horizontal Burning Test for Classifying Material
Specimens molded from the plastic material are oriented in either a horizontal depending on the specifications of the relevant test method, and they are subjected to a defined flame ignition source for a specified period of time.
UL 94 HB Rating
A material having a thickness between 3 and 13mm will be classified as a HB material if it does not have a burning rate exceeding 40mm per minute. For material with thickness less than 3mm the burning rate should not exceed 75mm per minute. The material will also be rated as HB if it ceases to burn before the 100mm mark independent of thickness.
| Test criteria | Burning rate in V | Flammability rating |
|---|---|---|
| Test specimen thickness 3-13mm | ≤40 mm/min | HB |
| Test specimen thickness < 3 | ≤75 mm/min | HB |
| Flame is extinguished before first mark | ≡ 0 mm/min | HB |
(Source: UL LLC)
UL 94 HBF: HBF, HF-1 and HF-2 – Horizontal Burning Foamed Material
This test grants three different types of ratings depending on burning rates and or after flame times. A material will be classified as a HBF material if it does not have a burning rate exceeding 40mm per minute over a 100 mm span or if ceases to burn before flaming or glowing reach the 125mm mark.
Flammability rating UL 94 HBF
| Test criteria (test specimens) | HF-1 | HF-2 |
|---|---|---|
| Burning time (s) | 4/5 ≤ 2 1/5 ≤ 10 | 4/5 ≤ 2 1/5 ≤ 10 |
| Burning and afterglow time of each individual specimen (s) | ≤ 30 | ≤ 30 |
| Dripping of burning specimen (ignition of cotton batting) | no | yes |
| Damaged length of individual specimen (mm) < | 60 | < 60 |
(Source: UL LLC)
Source: Omnexus Specialchem
