Fireproof Canvas Testing

Fire-resistant canvas inspection mainly conducts scientific testing and analysis on flame retardant performance testing, limiting oxygen index testing, thermal stability and high-temperature resistance testing, mechanical property testing, chemical medium resistance testing, and waterproof and weather resistance testing, objectively assessing the product quality grade and issuing a detailed test report within 3-7 working days, providing a basis for manufacturers' quality control and downstream users' product acceptance.

Testing Items

Flame retardant performance testing: This is the most core testing item of the fire-resistant canvas, aiming to evaluate the resistance ability of the material when contacting the fire source. The main tests are the char length, afterflame time and afterglow time after the material meets the fire in the vertical or horizontal state. According to the relevant standards (such as GB/T 5455), through the laboratory simulated flame contact, it is measured whether its damaged length is within the specified range, to judge its flame retardant grade.

Limiting oxygen index testing: This indicator is used to quantify the minimum oxygen concentration percentage (LOI) required for the material to maintain combustion. The higher the LOI value of the fire-resistant canvas, the more difficult it is to be ignited in the air. For example, the LOI of ordinary textiles is usually 18%-21%, while the LOI of a qualified fire-resistant canvas is usually required to be greater than 28% or even higher. This is the key parameter for evaluating its intrinsic flame retardant performance.

Thermal stability and high-temperature resistance testing: Tests the changes in the physical and mechanical properties of the canvas under a continuous high-temperature environment. Through the means such as thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), its decomposition temperature and mass loss rate are analysed, and whether it shrinks, melts or decomposes at high temperatures is evaluated, ensuring its safety in the specific high-temperature application scenarios (such as welding protection and high-temperature equipment covering).

Mechanical property testing: The flame retardant coating or treatment process may affect the mechanical properties of the canvas. Therefore, its breaking strength, tearing strength, abrasion resistance and bursting strength need to be tested. These tests ensure that while the canvas has the flame retardant function, it can still meet the basic requirements of strength, durability and tear resistance in actual use.

Chemical medium resistance testing: Evaluates the retention rate of the flame retardant performance and physical properties of the fire-resistant canvas after contacting chemical substances such as oils, acids and alkalis. The specimen is immersed in the chemical reagent of the specified concentration for a certain time, then taken out, washed and dried, and its flame retardancy and strength are tested again, to prevent the failure of the fire protection function caused by the chemical corrosion.

Waterproof and weather resistance testing: For the fire-resistant canvas used outdoors, its resistance to hydrostatic pressure, surface water resistance, UV aging resistance and damp-heat aging resistance need to be tested. It is ensured that under the climatic conditions such as rain and sunlight, the flame retardant coating does not fall off or powder, and the fire protection performance remains effective for a long time.

Smoke density and toxic gas testing: The high-level fire safety requirements not only pay attention to whether it burns, but also pay attention to the smoke concentration and the amount of toxic gas released during combustion. Through the equipment such as the smoke density chamber, the maximum specific optical density and the toxic components of the smoke during the material combustion are determined, to reduce the secondary hazards in the fire.

Testing Scope

Industrial welding and cutting protection field: Used for the isolation screens, spark guards and welding blankets of the welding workshops. The testing focus is on their ability to resist the splashing of the instantaneous high-temperature molten slag, requiring no melt-through and no spread of combustion after contact with the sparks, and the effective isolation of the radiant heat, protecting the surrounding equipment and personnel safety.

Warehouse logistics and cargo covering: Used for covering the flammable goods stacked in the open air (such as cotton and wood), the materials in transport, and as the tarpaulins of temporary warehouses. The testing needs to simulate the scenarios of rain soaking, long-term sunlight exposure and accidental fire source contact, ensuring their all-weather fire protection and waterproof performance.

Construction site protection: Applied to the fire-resistant isolation nets around the construction scaffolding, temporary safety barriers and building material covering. The testing needs to consider their wind load resistance, stain resistance and flame retardant performance, preventing the construction sparks from igniting, while meeting the safety code requirements of the construction sites.

Fire fighting and emergency rescue equipment: Used for making the emergency shelters of firefighters, the temporary containment booms for hazardous chemical leaks, and the equipment covering at fire scenes. The testing standards for the canvas of this use are the strictest. In addition to the basic flame retardancy, it also needs to have an extremely low smoke toxicity and a higher thermal radiation reflection or isolation performance.

Stage curtains and public place decorations: The curtains, background cloths and decorative fabrics used in the public places such as theatres, cinemas and exhibition centres. The testing strictly follows the fire safety regulations of the public places, emphasizing the low smoke, low toxicity and self-extinguishing, and the dripping materials after combustion cannot ignite other items, preventing the accidents of mass casualties.

Military and special vehicle equipment: Used for military tents, vehicle camouflage nets and equipment covers. The testing scope is extended to the combination of the camouflage performance (such as the infrared reflection characteristics) and the fire protection performance, as well as the functional stability under the harsh environments such as extreme high and low temperatures and salt spray.

Electric power and petrochemical industry: Used for the dust-proof and fire-resistant covers of the substation equipment, the outer protection of the oil pipeline insulation layers, and the temporary isolation of the refinery equipment. The testing needs to pay special attention to their antistatic performance, preventing the static accumulation from causing sparks, while requiring an excellent resistance to the oil media.

Testing Methods

Vertical burning method: In accordance with the GB/T 5455 (identical to ISO 6940/6941) standard, the canvas specimen of the specified size is vertically hung in a dedicated burning test chamber, ignited from its lower edge with a specified flame for a certain time, and after the fire source is removed, the afterflame time, afterglow time and damaged length of the specimen are precisely determined. This is the most classic and widely adopted method for assessing the flame retardant performance of fabrics.

Limiting oxygen index method: In accordance with the GB/T 5454 (identical to ISO 4589) standard, the specimen is vertically fixed at the top of a transparent combustion tube, and the tube is filled with the oxygen and nitrogen mixed in proportion. The specimen is ignited from the top, and by adjusting the oxygen concentration, the minimum oxygen concentration (LOI value) that can exactly maintain the stable combustion of the material is determined. This method has accurate results and good reproducibility.

45° inclined plane burning method: Mainly referring to the US FAR Part 25.853 standard or the automotive interior material standards. The specimen is inclined at 45 degrees, and its upper surface is ignited with a specific small flame, evaluating its burning rate and self-extinguishing. This method better simulates the burning behaviour of the material in the actual inclined state, and is commonly used for the testing of the transport vehicle interior materials.

Thermal radiation source method: Simulates the thermal radiation environment in a real fire, such as the radiant panel test in accordance with ISO 5657. The specimen is horizontally placed, subjected to the radiation of a heat source with a specified heat flux, and the time required for it to be ignited (ignition time) and the flame spread rate are determined. This method can more truly evaluate the reaction of the material in an overall fire.

Smoke density test method: In accordance with the GB/T 8627 (NBS smoke chamber method) or ISO 5659-2 standard. Under the specific burning or thermal radiation conditions, the degree of the light obscuration of the smoke generated by the material is measured, recording the maximum specific optical density and the smoke generation rate. This is the key method for evaluating the danger of the visibility reduction in a fire.

Thermogravimetric analysis method: Belonging to the instrumental analysis method. Under the programmed temperature control, the relationship between the mass of the canvas specimen and the temperature or time change is measured. Through the TGA curve, the information such as its thermal decomposition temperature and the weight loss ratio of each decomposition stage can be obtained, thereby analysing its thermal stability and the action mechanism of the flame retardant.

Cone calorimeter method: In accordance with the ISO 5660 standard, it is currently one of the most advanced fire performance test methods. Under the set external radiant heat flux, the sample is ignited, and multiple key fire parameters such as the heat release rate, mass loss rate, effective heat of combustion and smoke production rate are synchronously measured, enabling a comprehensive and scientific evaluation of the fire hazard of the material.

Testing Standards

Domestic Standards:

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

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

3. GB/T 8627, Test method for smoke density of building materials

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

5. 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 5659-2, Plastics — Smoke generation — Part 2: Determination of optical density by a single-chamber test

3. ISO 5660-1, Reaction-to-fire tests — Heat release, smoke production and mass loss rate — Part 1: Heat release rate (cone calorimeter method) and smoke production rate (dynamic measurement)

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

5. 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

Vertical burning tester: This equipment is the dedicated instrument for executing the standards such as GB/T 5455. The core components include a sealed burning test chamber, a propane or methane burner with precisely adjustable height, and an automatic ignition and timing device. The chamber is equipped with a specimen holder, marking lines and a heat-resistant glass window for observation, and can automatically record the afterflame and afterglow times. It is the essential equipment for the basic flame retardant testing in the laboratory.

Oxygen index tester: Used for the limiting oxygen index (LOI) testing. The equipment is mainly composed of a transparent pressure-resistant combustion glass tube, specimen clamp, gas mixing and flow control system, igniter and oxygen concentration monitor. The high-precision model can realize the automatic adjustment and stable control of the gas concentration, and directly display the LOI value digitally. The test results are objective and accurate.

Cone calorimeter: A large comprehensive fire testing instrument. The core principle is based on the oxygen consumption principle, and the equipment includes a radiation cone heat source, electronic igniter, precision balance, laser smoke meter, gas analysers (O₂, CO and CO₂) and a data acquisition system. It can simulate the real fire conditions and obtain multiple core parameters of the material combustion at one time. It is the key equipment for scientific research and high-end product testing.

Thermogravimetric analyser: Used for the thermal stability analysis of the material. The main body of the instrument is a high-precision micro balance, and the sample is placed in a furnace with programmed temperature control and heated in an inert or oxidizing atmosphere. The TGA can continuously and precisely record the curve of the sample mass changing with the temperature, with a sensitivity of up to the microgram level. It is an important analysis tool for studying the thermal decomposition behaviour and flame retardant efficiency of the fire-resistant canvas.

Smoke density test chamber: Used to measure the amount of smoke generated when the material burns. Taking the NBS smoke chamber as an example, it is a sealed cubic test chamber, internally provided with a sample holder, electric heating or propane burner, vertical light path system (light source and photoelectric receiver) and smoke exhaust purification device. The smoke density is calculated by measuring the light intensity attenuation after the light beam passes through the smoke.

Universal material testing machine: Used to test the mechanical properties of the fire-resistant canvas, such as the tensile, tearing and bursting strengths. The equipment drives the grips through a precise servo control system, applying a uniform tensile or bursting force to the specimen, and the force sensor and displacement sensor collect the data in real time, generating a stress-strain curve, thereby calculating the various mechanical property indicators.

Environmental aging test chamber: Including the UV aging chamber, xenon lamp aging chamber and constant temperature and humidity chamber. Used to simulate and evaluate the weather resistance of the fire-resistant canvas. By controlling the conditions such as the light intensity, temperature, humidity and spraying in the chamber, the accelerated aging tests are carried out, and the flame retardant performance and physical property changes of the aged samples are periodically tested, predicting their service life.