Summary of flame retardant performance testing methods and standards

There are many products that require flame retardant performance testing, such as fireproof/refractory material products, building material products, plastic material products, coating products, etc. These products will have very high requirements for flame retardant performance, and the flame retardant performance testing method There are still many. Today we will give you a detailed introduction to the three common flame retardant tests, namely horizontal burning test method, vertical burning test method and oxygen index method, from standards to specific detection methods.

 

 

 

The horizontal combustion test method is to test the combustion performance of the sample under horizontal support under laboratory conditions. There are many standards for horizontal combustion test methods, mainly for testing wires and cables, plastics, leather, and blankets.

 

1. Horizontal combustion test testing standards

GB/T 12666.2-2008 Single wire and cable combustion test method Part 2: Horizontal combustion test

GB/T 8332-2008 Test method for combustion performance of foam plastics - Horizontal combustion method

MH/T 6047-2008 Four-layer horizontal burning test method for aviation blankets

QB/T 2729-2005 Leather Physical and Mechanical Testing Determination of Horizontal Combustion Properties

 

2. Specific test methods for horizontal burning test

(1) Test device

The test was conducted in a combustion box, with a Bunsen burner with an inner diameter of 9.5mm installed on the left inner side of the box. There is a specimen clamp for fixing the specimen on the right side. The Bunsen burner is tilted upward at 45 degrees and equipped with an advance and retreat device. The gas used for the test is natural gas, petroleum gas or coal gas, and a stopwatch and caliper are provided.

 

(2) Test method

A. Specimen preparation

Each material requires 5 test pieces. Each test piece must be flat and smooth, without bubbles, 125±5mm long, 13.0±0.3mm wide, and 3.0±0.2mm thick. Tests can also be conducted on samples with a thickness of 2-13mm. , but the results can only be compared between the same thicknesses.

 

B. experiment procedure

First, draw a marking line on the wide surface of the specimen at a distance of 25 mm and 100 mm from the ignition source. Then place the specimen horizontally with its long axis, and fix the cross-sectional axis on the specimen clamp at an angle of 45 degrees to the horizontal. Place a water pan 300mm below it. Ignite the Bunsen burner, adjust the flame length to 25mm and turn it into a blue flame, and apply the tip of the flame core to a length of about 6mm from the lower edge of the sample. And start timing, the flame application time is 30 seconds. The Bunsen burner must not be moved during this period, but during the test, if the specimen burns to the first mark in less than 30 seconds, the flame application should be stopped immediately. After stopping the flame, the following observations and records should be made.

a) Whether there is visible flame in 2S;

b) If the sample continues to burn, record the time t it takes for the flame front to go from the first marking line to the second marking line, and find its burning speed V: V=75/t (mm/min)

c) If the flame is extinguished before reaching the second mark, record the burning length S: S = (100-L) mm. Where: L - the shortest distance from the second mark to the unburned part, accurate to 1mm. Observe other phenomena, such as melting, curling, carbonization, dripping and whether the dripping material burns, etc.

 

C． Assessment of results

Each test is classified as follows: a. GB2408-80/Ⅰ: The sample is extinguished within 2 seconds after the fire source is removed b. GB2408-80/Ⅱ: The flame front is extinguished before reaching the second mark. At this time, the burning length S of the sample should be reported (if the burning length is 50mm, the report is GB2408-80/Ⅱ-50mm) c. GB2408-80/Ⅲ: When the flame front reaches or exceeds the second marking line, the burning speed V should be reported at this time (if the burning speed is 20mm/min, the report is GB2408-80/Ⅲ-20mm/min). The test results are based on 5 tests. The material is rated for the category with the largest number in the piece, and the maximum burn length or burn rate is reported.

 

 

The vertical combustion method is a method of classifying the combustion of vertically placed samples with certain specifications under the action of flame under specified conditions.

 

1. Vertical combustion test testing standards

GB 32086-2015 Technical requirements and test methods for vertical combustion characteristics of specific types of automotive interior materials

GB/T 12666.1-2008 Single wire and cable combustion test method Part 1: Vertical combustion test

GB/T 8333-2008 Test method for combustion performance of rigid foam plastics - Vertical combustion method

JB/T 4278.18-2011 Verification method for rubber and plastic wire and cable testing instruments and equipment Part 18: Vertical combustion test device for single copper core insulated thin wire and cable

JB/T 4278.5-2011 Verification methods for rubber and plastic wire and cable testing instruments and equipment Part 5: Single insulated wire and cable vertical combustion test device

JJF (Textile) 068-2016 Calibration Specifications for Vertical Combustion Tester

JJF (Textile) 068-2018 Calibration Specifications for Vertical Combustion Tester

FZ/T 98017-2018 Textile vertical combustion performance tester

 

2. Specific test methods for vertical combustion test

(1) Test device

The test was conducted in a combustion box with internal dimensions of 329 mm × 329 mm × 780 mm. There is an exhaust hole with a diameter of 150mm on the top of the combustion box. In order to prevent the influence of external air flow on the test, a top plate is added 25mm away from the top of the box. A specimen clamp support is installed on the right side of the combustion box to ensure that the test specimen can be fixed. Located in the center of the combustion box. A Bunsen burner tilted upward at 45 degrees is installed on the left side of the box. Fixed on the horizontal slide of the control box. Place a stand for absorbent cotton in the lower part of the box. Other spares include stopwatch and caliper.

(2) Test method

A. Test pieces: Each group of samples requires 5 test pieces, which are required to be flat, smooth and free of bubbles. Length 130±3mm, width 13.0±0.3mm. Thickness 3.0±0.2mm. The prepared specimens shall be conditioned under standard climatic conditions for 48 hours.

B. Test steps: The test piece is fixed vertically on the solid part clamp, and the clamped part at the upper end of the test piece is 6mm. Place absorbent cotton. Ignite the Bunsen burner 150mm away from the specimen, adjust the flame height to 20±2mm, and produce a blue flame. Place the center of the Bunsen burner 10mm from the lower end of the specimen, and aim the flame at the center of the lower end of the specimen. start the timer. When the flame is applied to the specimen for 10 seconds, the fire source is removed, and the flaming burning time of the specimen is recorded. After the flaming burning of the specimen is extinguished, apply the flame for another 10 seconds according to the above method, and record the flaming and non-flaming time of the specimen after removing the flame. Flame burning time.

C． For the evaluation of the results, the combustion performance of the test piece is defined as FV-0, FV-1, FV-2, level three as follows.

V-0: The vertical sample stops burning within 10 seconds; no droplets are allowed;

V-1: The vertical sample stops burning within 30 seconds; no droplets are allowed;

V-2: The vertical sample stops burning within 30 seconds; burning material is allowed to drip.

If one of a group of 5 samples does not meet the requirements in the table, another group of samples should be taken for testing, and the second group of 5 samples should all meet the requirements. If there is still one sample in the second group that does not meet the corresponding requirements in the table, the grade with the highest value in the two groups will be used as the grade of the material. If the test results exceed the requirements of item VF-2, the material cannot be evaluated for oxygen index using the vertical combustion method.

 

 

There are still many products suitable for flame retardant performance testing-oxygen index method, such as viscose, polyester fiber, synthetic fiber, plastics, textiles, asphalt, etc.

 

1. Flame retardant performance test-oxygen index detection standard

FZ/T 50016-2011 Test method for flame retardant properties of viscose short fibers Oxygen index method

FZ/T 50017-2011 Test method for flame retardant properties of polyester fiber Oxygen index method

FZ/T 50029-2015 Test method for flame retardant properties of synthetic fiber raw material slices Oxygen index method

GB/T 16581-1996 Test method for combustion performance of insulating liquids Oxygen index method

GB/T 2406.1-2008 Plastics Determination of combustion behavior by oxygen index method Part 1: Guidelines

GB/T 2406.2-2009 Plastics Determination of combustion behavior by oxygen index method Part 2: Room temperature test

GB/T 5454-1997 Textiles - Combustion performance test - Oxygen index method

GB/T 8924-2005 Test method for combustion performance of fiber reinforced plastics Oxygen index method

GSB 08-3562-2019 Plastic (PMMA) oxygen index standard sample

NB/SH/T 0815-2010 Determination of asphalt combustion performance Oxygen index method

TB/T 2919-1998 Test method for fabric combustion oxygen index

 

2. Flame retardant performance test-oxygen index specific test method

 

1) Refer to GB2406 "Test Methods for Combustion Performance of Plastics - Oxygen Index Method", which stipulates that when clamping a plastic whose lower end can stand upright, the burning time of the sample is 3 minutes, and a marking line is drawn from the wide surface of the sample 50mm away from the ignition end. When the burning time of the sample exceeds 3 minutes or the flame front exceeds the marking line, the oxygen concentration is reduced. When the burning time of the sample is less than 3 minutes or the flame front does not reach the marking line, the oxygen concentration is increased. Repeat this process until the obtained oxygen concentrations are equal to The difference is less than 0.5%.

 

2) Test method

A. Specimen preparation

Each group of samples should have 5-10 test pieces. Each test piece is 70-150mm long, 6.5±0.5mm wide, and 3.0±0.5mm thick. The surface of the test piece is required to be flat and smooth without bubbles.

 

B. experiment procedure

Before the test is carried out, a scale line should be drawn on the test piece 50mm away from the ignition source, and then installed vertically on the test piece clamp. The distance from its upper end to the combustion tube should be greater than 10mm. The initial oxygen concentration should be estimated and adjusted. It should be kept burning at all times. The air flow velocity in the barrel is 40±10mm/s. Let the adjusted air flow flow for 30 seconds to clean the combustion tube. Then use an igniter to ignite the top of the specimen. When it is confirmed that the top of the specimen is completely ignited, remove the igniter and start timing. At this time, the flow rate and oxygen concentration must not be changed arbitrarily. During the test, if the burning time of the sample exceeds 3 minutes, or the flame front exceeds the marking line, the oxygen concentration should be reduced before testing again. , otherwise the oxygen concentration should be increased. When the difference between the increase or decrease in the oxygen concentration value is less than 0. At 5%, the oxygen index of the material should be calculated based on the reduced oxygen concentration value. Three tests were performed within this range. ,

 

C． Result calculation

The calculation formula of oxygen index (OI): OI=[O2]/[O2]+[N2]×100% where [O2]——oxygen flow rate L/min: [N2]——nitrogen flow rate L/min. three times The average of the test results is the oxygen index of the material.

The oxygen index of various organic polymers has been measured. Generally, substances with OI≥27 are flame retardant substances.

 

D． discuss

Factors affecting oxygen index

 

a. flow rate

At 30 and 120mm/s, the OI is almost independent of the gas flow, which must be fast enough to clear the burned gases from the nearest atmosphere, but not so fast as to increase the mixing velocity at the fire front.

 

b. Thickness of sample

As the sample becomes thinner, the material becomes more flammable and the oxygen index value decreases.

 

c. pressure

The OI behavior of some polymers is sensitive to reduced pressure, possibly due to accelerated degradation of the polymer through continued product removal.

 

d. Inert gas

When Ar, Ne, and CO2 gases are used, the oxygen fraction (OF) required to maintain combustion is expressed as: OF = [O2] / [inert gas]

The OF value increases linearly with the heat capacity of the gas. When Hr is used, the OI value is 50% greater than expected. This is due to the high thermal conductivity of Hr gas that takes away heat from the flame.

 

e. temperature

Temperature has a great influence on OI, and temperature has little influence on OI at room temperature. Various polymer OIs have different temperature dependences at elevated temperatures.

 

f. Relationship between value and ignition position

Bottom ignition and top ignition can obtain different oxygen index values. Bottom ignition is closer to the actual combustion situation than top ignition, and its oxygen index value is much lower.

 

The above are the three most common test methods for flame retardant performance testing. The flame retardant performance testing method still needs to be selected according to the specific product and customer needs. The three test tests mentioned above are all based on plastic resistance. The combustion test is used as a reference. Products suitable for flame retardant performance testing include automotive interior materials, electronic products, electrical products, furniture, mattresses, etc.