Fire-resistant Webbing Testing

Fire-resistant webbing testing mainly conducts scientific testing and analysis on limiting oxygen index determination, vertical burning testing, thermal protective performance testing, high-temperature resistance testing, smoke density testing and toxic gas analysis, objectively assessing the product quality grade and issuing a detailed test report, providing a basis for manufacturers' quality control and downstream users' product acceptance.

Testing Items

Limiting oxygen index determination: Determines the minimum oxygen concentration percentage (LOI) required for the fire-resistant webbing to maintain combustion, which is the basic indicator for evaluating its flame retardancy. The higher the LOI value, the more difficult the material is to ignite and sustain combustion in air. Usually, the LOI value of fire-resistant webbing needs to be significantly higher than the 21% oxygen concentration in air.

Vertical burning testing: Simulates the burning behaviour of the webbing in contact with a fire source in a vertical state. The main evaluation indicators include the afterflame time, afterglow time and damaged length, to judge whether the webbing can quickly self-extinguish after the fire source is removed. It is the key test for evaluating its ability to prevent flame spread.

Thermal protective performance testing: Evaluates the heat transfer capability of the webbing to the simulated skin (sensor) on the back side when in contact with high temperature or flame. By measuring the time required to cause a second-degree burn (TPP value), its thermal insulation effectiveness as a component of protective equipment is directly reflected.

High-temperature resistance testing: The webbing is placed in a specific high-temperature environment (such as 260 ℃ and 500 ℃) for the specified duration, and then the retention rate of its physical and mechanical properties (such as the breaking strength) is tested. This item concerns the structural integrity and functionality of the webbing in the high-temperature environment of a fire.

Smoke density testing: Measures the optical density of the smoke generated by the fire-resistant webbing during incomplete combustion or pyrolysis. A lower smoke density means better visibility can be provided in a fire, which is crucial for personnel evacuation and fire rescue.

Toxic gas analysis: Detects the types and contents of toxic gases released by the fire-resistant webbing under specific combustion conditions, such as carbon monoxide, hydrogen cyanide, hydrogen chloride and sulphur dioxide. This indicator is directly related to the poisoning risk of personnel in a fire, and is an important consideration of modern fire safety.

Testing Scope

Firefighter personal protective equipment: Mainly used to test the load-bearing straps, adjustment straps and suspension straps used on firefighting suits, rescue helmets, fire gloves and other equipment. It is necessary to ensure that they maintain strength and function in extreme fire scene environments, without melt dripping or shrinkage, effectively protecting the safety of firefighters.

Industrial high-temperature protection field: Applied to the connecting and fixing webbings of high-temperature protective clothing, heat insulation blankets and protective equipment in industries such as metallurgy, electric power and welding. The testing focus is on their long-term heat resistance, thermal radiation resistance and the reaction when in contact with high-temperature molten metal slag.

Transportation safety: Covering the seat belts, cargo fixing straps and escape slide webbings of vehicles such as aircraft, high-speed trains and ships. In addition to the fire resistance and flame retardancy, comprehensive properties such as high strength, abrasion resistance and weather resistance also need to be tested in combination.

Military and special equipment: Including the webbing components of special clothing such as military combat uniforms, tank crew uniforms and flight suits, as well as the fixing straps of military tents and equipment. The testing standards are usually more stringent, requiring stable fire resistance performance in a variety of complex and harsh environments.

Public places and building fire protection: Involving the curtain hoisting straps and safety isolation straps in places such as cinemas, theatres and stadiums, as well as the hose binding straps and fire shutter control straps in building fire protection systems, which need to meet the corresponding building fire protection code requirements.

Home textiles and children's products: Such as the tie-backs of high-end flame-retardant curtains, the fixing straps of bedding, and the decorative straps and adjustment straps that comply with the children's sleepwear safety standards. Testing focuses on preventing ignition by small fire sources (such as candles and lighters) and controlling the flame spread speed.

Testing Methods

Oxygen index method: In accordance with standards such as GB/T 5454, ISO 4589-2 and ASTM D2863, the specimen is vertically fixed in a burning tube, with the upward flowing oxygen-nitrogen mixed gas used as the combustion-supporting gas. By gradually adjusting the oxygen concentration, the minimum oxygen concentration value that can support the specimen to sustain combustion for at least 3 minutes or reach a damaged length of 50 mm is found.

Vertical burning test: In accordance with standards such as GB/T 5455, ISO 6941 and ASTM D6413, a standard methane flame is used to ignite the lower end of the vertically hung specimen for 12 seconds. After the fire source is removed, the afterflame time and afterglow time are precisely recorded, and the carbonized damaged length of the specimen is measured, thereby evaluating the flame retardant effect.

Thermal protective performance (TPP) test method: In accordance with standards such as GB/T 17599, ISO 17492 and the annexes of NFPA 1971, a heat source with a specific heat flux (usually 84 kW/m²) is used to carry out radiation and convection heating on the specimen. The heat accumulation curve is recorded by the copper calorimeter on the back side, and the time required to cause a second-degree burn is calculated.

Thermogravimetric analysis and differential scanning calorimetry: TGA and DSC instruments are used to measure the mass change and heat flow change of the webbing material under programmed temperature control. By analysing its thermal decomposition temperature, decomposition rate, residual char content and endothermic/exothermic peaks, its flame retardant mechanism and thermal stability are studied from the material science perspective.

Cone calorimeter test method: In accordance with the ISO 5660-1 standard, the specimen is ignited under a set radiant heat flux (such as 25 kW/m² or 50 kW/m²), and key fire performance parameters such as the heat release rate, total heat release, effective heat of combustion, mass loss rate and smoke production rate are synchronously measured, providing a more comprehensive evaluation.

Toxic gas test method: Usually in accordance with NES 713 or through gas analysis techniques such as a tube furnace or cone calorimeter combined with Fourier transform infrared spectroscopy (FTIR), the gas is collected under specific combustion conditions, and the generation amounts of various toxic and harmful gases such as carbon monoxide and hydrogen cyanide are qualitatively and quantitatively analysed.

Testing Standards

Domestic Standards:

1. GB/T 5454-1997, Textiles — Burning behaviour — Oxygen index method

2. GB/T 5455-2014, Textiles — Burning behaviour — Determination of damaged length, afterglow time and afterflame time

3. GB 18401-2010, National general safety technical code for textile products

4. GB/T 3920-2024, Textiles — Tests for colour fastness — Colour fastness to rubbing

International Standards:

1. ISO 4589-2, Plastics — Determination of burning behaviour by oxygen index — Part 2: Ambient-temperature test

2. ISO 6941, Textile fabrics — Burning behaviour — Measurement of flame spread properties of vertically oriented specimens

3. ISO 13934-1, Textiles — Tensile properties of fabrics — Part 1: Determination of maximum force and elongation at maximum force using the strip method

4. ISO 105, Textiles — Tests for colour fastness

Note: The applicable standard can be selected according to the product use and customer trade requirements; standards agreed in the contract take precedence over general standards.

Testing Instruments and Equipment

Oxygen index tester: The core components include a heat-resistant glass burning tube, a specimen holder, a precision gas mixing and flow control system, an igniter and a timing device. High-precision models are equipped with automatic oxygen concentration search and result calculation functions, ensuring the accuracy and repeatability of the test results.

Vertical burning test chamber: The main body of the equipment is a stainless steel combustion chamber, with a built-in standard Bunsen burner, specimen holder, automatic ignition and timing system, and an exhaust device. The front of the chamber is provided with a high-temperature-resistant glass observation window, facilitating safe operation and recording of the combustion process.

Thermal protective performance (TPP) tester: Composed of a radiant heat source (usually a quartz lamp tube array), a convection burner, a specimen holder, a copper calorimeter sensor, a data acquisition system and a calibration device. It can precisely simulate the mixed heat transfer mode, and is the equipment for evaluating the thermal insulation capability of protective materials.

Cone calorimeter: A large comprehensive fire testing instrument, mainly including a radiation cone heat source, an electronic igniter, a specimen loading platform, an exhaust gas collection hood, a laser smoke density measurement system, a paramagnetic oxygen analyser and a gas filtration device. It calculates the heat release rate through the oxygen consumption principle, and is the "gold standard" equipment for studying the combustion behaviour of materials.

Thermogravimetric-infrared combined system: The thermogravimetric analyser (TGA) is connected to the Fourier transform infrared spectrometer (FTIR) through a high-temperature transfer line. The TGA monitors the mass change of the material during thermal decomposition in real time, and the FTIR synchronously analyses the composition of the gaseous products released by decomposition. It is a powerful tool for studying the flame retardant mechanism and pyrolysis behaviour.

Smoke density test chamber: Designed in accordance with standards such as GB/T 8323 and ASTM E662. The chamber body is a closed dark box, with a standard heat radiation source or open-flame burner, a vertical light path system (including a light source, lens, light trap and photoelectric detector) inside. The specific optical density is calculated by measuring the transmittance attenuation of the light beam through the smoke.