Flame retardant rating of heat shrinkable tubes

Overview

VW-1 is the fire resistance rating of the wire. UL,VW-1 test standard, the test stipulated that the sample should be kept vertical, with the test blowtorch (flame height 125mm, thermal power 500W) burning for 15 seconds, then stop for 15 seconds, repeated 5 times. Eligibility criteria are:

1. Residual flame shall not exceed 60 seconds;

2. The sample can not burn more than 25%;

3. The surgical cotton pad at the bottom shall not be ignited by falling objects.

Classification

There are 12 types of UL94: HB, V-0, V-1, V-2, 5VA, 5VB, VTM-0, VTM-1, VTM-2, HBF, HF-1, hF-2.

Flammability UL94 is the most widely used standard for flammability of plastic materials. It is used to evaluate the ability of materials to extinguish after ignition. There are a variety of ways to judge whether a drop burns, according to the rate of combustion, the duration of combustion, the ability to resist droplets, and whether the droplets burn. A number of values can be obtained for each material being tested, depending on its color or thickness. When a material is selected for a product, its UL rating shall meet the thickness requirements of the wall part of the plastic part. UL grade should be reported with thickness value, it is not sufficient to report UL grade without thickness.

The flame retardant grade of plastics increases step by step from HB, V-2, V-1,V-0,5VB to 5VA:

HB: The lowest flame retardant rating in the UL94 standard. Requires a combustion rate of less than 40 mm per minute for samples 3 to 13 mm thick; For samples less than 3 mm thick, the combustion rate is less than 70 mm per minute; Or go out at the 100mm sign.

V-2: Residual flame & residual burn out in 60 seconds after two 10-second burn tests on the sample. The falling particles can ignite cotton.

V-1: Residual flame & residual burn out in 60 seconds after two 10-second burn tests on the sample. Falling particles cannot ignite cotton.

V-0: Residual flame & residual flame extinguished within 30 seconds after two 10-second burn tests on the sample. Falling particles cannot ignite cotton.

5VB: Residual flame & residual flame will be extinguished within 60 seconds after five 5-second combustion tests are performed on the sample. Falling particles cannot ignite cotton. Burn through is allowed for block samples.

5VA: Residual flame & residual flame will be extinguished within 30 seconds after five 5-second combustion tests are performed on the sample. Falling particles cannot ignite cotton. It is not allowed to burn through bulk samples.

UL1581 wire burning mode:

1. VW-1: vertical combustion test (UL wire combustion grade)

2. FT1: Vertical combustion test;

3. FT2: horizontal combustion test;

4. FT4: Vertical combustion test;

5. FT6: Horizontal combustion and smoke test. (THE FT class is the CSA standard wire combustion class).

Among the above levels:. Vw-1 and FT1 have the same level. FT2 is the easiest to pass and has the lowest rating (FT6> FT4> FT1> FT2).

VW-1 is strictly stricter than FT1, both of which are vertical burning. The criteria are as follows :

1. The burning mark (kraft paper) cannot be carbonized by more than 25%; 

2. Five 15-second burns shall not exceed 60 seconds; 

3. Burning droplets can not ignite cotton; 

Vw-1 requires 1, 2, 3; FT1 requires only 1,2.

For the wire industry:

V-2, V-1, V-0, 5VA and 5VB of UL 94 are tested for the materials used in the wire. Standard samples shall be prepared by using additional test materials and will not be marked on the wire. 

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

The flame retardance of wires is completely different from the flame retardance of UL94, for example an insulating material can pass through THE V-0 of UL94 but not necessarily through THE VW-1;

In addition, UL94 is the flame retardant of insulating materials, and the flame retardant requirements of wires are generally in UL758 62 1581; Different objects;

So V-0 V-1 UL94 inside the flame retardant is not the flame retardant wire; Vw-1 /FT1 is not printed on AWM wire and V0 combustion test in UL94 is very different in equipment:

1. The height and temperature of the flame are different;

2. The methane flow rates used in the tests are also different;

3. Methane also has a different back pressure;

4. The volume of the combustion chamber is also different: VW-1 requires more than 4 cubic meters, while V0 only requires more than 0.5 cubic meters;

5. the number of combustion is different;

6. In the combustion results: V0 requires the recording of residual burning time, but VW-1 does not.