How To Test Flame Retardant Properties in Fabrics?

Statistics show that one of the major reasons for fatalities in the event of a fire is the accidental ignition of textiles. Therefore, there is a need for proper flammability standards that can be verified through the conduction of flame retardant fabric testing. It has become a critical safety implication to decrease the likelihood of fatalities and injuries in case of a fire. Fabric testing for flame retardant properties can also help the fabric manufacturer improve the flammability performance and make clothing safer.

However, all flame retardant tests for fabric are not the same, and it is important to identify the specific environment and application where the fabrics will be used. This may help determine which flame retardant test the fabrics must pass. This article provides a brief insight into the most commonly used test methods that are considered a benchmark to assess the flame retardant properties of a fabric.

Flame Retardant Fabric Classification

Fabric is categorized variably according to its fire retardant properties. For instance, a fabric certified to be flame retardant is topically treated with a chemical after its weaving process. Natural fibers like cotton are categorized as flame retardant when topically treated with fire retardant chemicals. However, topical treatments can wear out over time, particularly if regularly cleaned. 

Another category is permanently flame retardant fabrics. These are the fabrics that are woven from non-combustible fibers, and their fire retardant characteristic will last for the fabric’s life. Even if the fabric is cleaned, its fire retardant properties will not dissipate. 

Flame-Retardant Test for Fabric

Fabric flame retardant test methods vary in terms of purpose, equipment, and principles, and it is hard to compare the results of the various methods. However, in any case, the tests are intended to measure the fabric’s flammability when it is exposed to a certain flame source. The flame retardant certification is provided after the conduction of the tests to endorse that the fabric has passed certain criteria and is safe for use in different environments. 

Flame retardant testing can be confusing for customers, particularly if they do not have the know-how of flame retardant criteria. To make it easier, here are a few tests conducted specifically for protective garments usually worn in the industrial setting. 

Flame Retardant Clothing standards

The flame retardant standard for clothing, known as NFPA 2112, is used to assess protection against hazards of industrial flash fires like oil and gas or petrochemical industries. Similarly, the NFPA 70E standard is used for assessing protection against the thermal hazards of electric arcs from welding processes. While the NFPA requires third-party endorsements, the NFPA 70E is a self-declaration test. 

Continue reading to learn what kinds of tests are run to ensure the flame retardant properties of fabrics.

Vertical Combustion Test Method for protective clothing

The vertical flame test is done to specify the garment’s protection level against heat and ignition. It is based on the fabric’s burning rate and determines the standard it must meet to provide protection when it is presented with fire in a vertical flame test. The textile product that meets the standard requirement is considered to be flame retardant. 

For this test, every individual layer of the group is tested separately. If the fabric tag specifies that the fabric must be washed, then the fabric needs to be tested before and after at least a hundred washing and drying cycles. The standard time for flame exposure for this test is twelve seconds.

Once the fabric is exposed to flame and cooled down, an appropriate amount of weight is hung to provide an adequate amount of tearing force. The material and the reflective tape usually used in fire retardant garments must have a charred length of around four inches, and the post-burning duration must not be more than two seconds. Moreover, the fabric must not drip or melt.

To conduct the test, a fabric sample of a certain size is vertically placed in a combustion test chamber and is ignited for twelve seconds via a pre-specified ignition source. Once the source is removed, the fabric’s protraction and burning time are measured. Once the smoldering stops, the fabric’s charred or damaged length is measured per the stated method. The vertical combustion method is usually used to ascertain the flame retardant characteristics of garments, decorative fabric, tent fabric, etc. 

Fabric Flame Retardant Testing Via Special Equipment

Another method through which manufacturers can test the flame retardant properties of textiles involves the use of special equipment. A flame retardant box is used that is suitable for testing the flame retardant characteristics of garments, tents, or decorative fabric. This method is usually employed in scientific research departments, the rubber industry, or textile inspection units.

The flame retardant box is designed to conform to a set of standards outlined for the vertical combustion performance test for textiles and also the standards for fire-blocking materials.

The box used an electrical heating wire ignition and automatically records the fabric’s burning continuation time after exposure to ignition and its flame retardant time.

The timing for the ignitor is set anywhere between 0 and 100 seconds, but the standard is twelve seconds. Moreover, the height of the flame can be adjusted while the temperature gauging device can also be configured.

The Test Method for Protective Clothing Used in Welding and Similar Processes

Tests are also conducted to ensure the flame retardant properties of fabrics used for protective clothing worn for welding or another similar process. These tests are conducted according to standards that specify the basic minimum security requirement the fabric must meet that is used for protective clothing and relevant processes with comparable risks. 

The protective clothing subjected to these test methods is usually worn for welding and similar processes. It is intended to protect the wearer against molten metal splashes and radiating heat from the electric arc used in processes like welding. It is suitable for instances where the contact time with flame is short. The protective clothing passing this test also lowers the risk of electrical shock due to short-circuiting, whereby the short contact occurs with the electrical conductors having a voltage of up to around 100V.

There are a variety of testing methods with variable compliance values that ensure protection against flames and heat, and small molten splashes. Specific tests also measure the clothing’s electrical resistance and the fabric’s tensile and bursting properties.

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