A Complete Guide to Flame Retardant Fabrics and Flame Retardant Testing

 

Flame retardant testing for textiles is essential for user safety and international compliance. Flame resistance testing involves exposing a fabric to flame to determine its extinguishing behavior, resistance to fire, and char length in case of fabric damage. Different ISO and ASTM standards evaluate textiles’ flame resistance. Here, we will discuss Flame Retardant Fabrics and Flame Retardant Testing.

What is Flame Retardant Fabric?

Flame retardant (FR) fabrics are made of inherently non-flammable or permanently flame-retardant fibers.

Fabrics that do not have inherently FR properties are treated with FR finishes, which slow down the impact of fire and develop the cloth’s self-extinguishing property.

Regular non-FR fabrics are treated with a special coating to protect them against fire.

Flame-resistant clothing, formerly known as flame retardant clothing, is a specialized piece of personal protective clothing required in many workplaces. Flame-resisting clothing, or FR clothing, is used in occupations involving inherent risks of fire explosion or contact with energized electrical equipment.

 

Industries and occupations that use FR clothing as a final method to control these hazards include electricians, electric utility repair and maintenance, refineries, pharmaceutical and chemical work, paper and pulp manufacturing, and food processing.

If you or your employees require FR clothing to carry out work safely, here are some key things worth knowing.

Self-Extinguishing

Flame-resistant clothing is self-extinguishing. Unlike conventional fabrics, flame-resistant material is, by definition, self-extinguishing. It will not fuel a fire; rather, it will starve a fire by preventing the entrance of oxygen through the material.

The material will naturally extinguish the fire if exposed to a brief intermittent flame while wearing this clothing. This ability significantly lowers the wearer’s risk of burn injury and can often provide valuable time to escape the unsafe environment.

Inherently Flame Resistant

Some materials are naturally flame resistant, and some manufacturers make products that are naturally flame resistant and do not need to be chemically treated to be classified under the FR standard.

Natural fibers like wool and silk typically do not melt and are difficult to ignite, making them good candidates for FR gear. The tighter and heavier the wool, the more fire-resistant it is.

Some synthetic fibers, like polyester and nylon, are also more difficult to ignite; however, once they catch fire, they tend to melt. Like wool, the tighter the weave, the more flame-resistant the fabric will be.

One advantage of inherently flame-resistant fabrics is that they are engineered to be flame-resistant for eternity. Since their FR properties are incorporated at the molecular level, they offer fire protection that doesn’t wash out or wear out.

Chemical FR Treatments

Other fabrics can still be made flame-resistant. Natural fabrics like linen and cotton can ignite easily and result in a rapid spread of flame, but they can be treated with chemicals that will extinguish the flame.

Alternative manufacturers treat clothing with a compound at the final production stage. This compound extinguishes fire by depriving it of the oxygen required to keep burning.

One downside to these treated fabrics is that their FRP properties will degrade over time and offer less and less protection as UV exposure, abrasions, and washing erode their performance.

Another concern is that chemical FR treatments applied to fabrics like cotton can have negative environmental effects. For example, the effluents produced in the process could find their way into and contaminate the natural environment.

Brominated Flame Retardants (BFRS)

Flame-resistant material can be toxic. A common question about flame-resistant clothing is whether it is toxic. The answer isn’t always straightforward, but chemical FR treatments applied to fabrics such as cotton regularly present serious environmental concerns.

Currently, the largest marketed FR group is brominated flame retardants (BFRS).

It is the largest distributed product worldwide due to its combination of high effectiveness and low cost. Approximately 75 BFRS are presently recognized.

However, some of these have been removed from the marketplace since the 1970s following incidental poisoning due to ingestion, which demonstrates the toxicity of those specific classes.

FR Clothing Considerations

Several FR clothing considerations come into play when purchasing or using FR clothing.

After assessing the risks and becoming familiar with the job tasks the user will be performing, start by considering which style and weight of FR garment is more suitable and practical for the worker.

What arc thermal performance value is required? This value outlines the performance of Fr material when it is exposed to electrical discharge.

Does the FRP product meet safety standards and regulatory requirements? What is the life expectancy of the garment, and how soon will it have to be replaced?

This information will help you make an educated choice regarding FR clothing, but it’s not the end of your search.

Investing the time and money required to do the research and select the right products will ensure durability, comfort, and, most importantly, confidence that you’re getting the protection needed.

How to Test Flame Retardant Fabrics?

How are FR fabrics tested? Safety standards require flame-resistant fabrics to be tested to verify that they will consistently and effectively perform their primary job of either self-extinguishing or not igniting.

Depending on the hazards the fabric is intended to protect against and the applicable safety standards. A variety of different tests may be necessary.

Different methods are used to measure the performance of FR clothing. The most basic test is the ASTM D 64 13 flammability test, also known as the vertical flame test. Let’s see the common standard for FR testing of fabrics.

ASTM D 6413 Vertical Flame Method

The most fundamental test in determining whether a garment is flame resistant is called the vertical flame test. In this test, a strip of fabric is placed in a holder and exposed to an open flame for 12 seconds.

 

After the exposure, the fabric is monitored for afterburn, and the damaged area of the sample is measured to determine the char length.

American Society for Testing and Materials developed the test method for vertical flame, ASTM D6413. Let’s look at how this test is conducted. The strip of the fabric being tested is placed in the chamber and exposed to a flame for 12 seconds.

 

 

After 12 seconds, the flame is shut off. Two things are measured. The after-flame is how long the fabric Swatch continues to burn after the flame is shut off, and the Char length is the length of the brake in the fabric due to charring.

It’s measured like this: the Char length is about 3.5 inches.

Various standards will outline the maximum acceptable Char length, and the vertical flame is a critical test to establish whether a fabric will self-extinguish.

But it does not predict protection level on everything, like an arc rating. For example, let’s look at this test being conducted. In this test, a strip of navy blue FR fabric is hanging in the center of the chamber, ready to be tested.

The test device is turned on, and the flame begins to burn at the bottom of the strip. The timer on the left is counting down from 12 seconds. After 12 seconds of exposure, the flame stops, and the time of any after-flame is measured.

The fabric strip will then be removed from the device to measure the Char length. Now we know how the vertical flame test works.

Let’s look at where it is referenced in some key standards. The first standard we’ll discuss is ASTM F1506. It specifies the minimum performance requirements to protect against arc flash exposure.

ASTM F1506 Electric Arc Flash Side

This standard gives performance specifications for flame-resistant textile materials for wearing apparel or use by electrical workers exposed to momentary electric arc and related thermal hazards.

Fabrics are evaluated based on their performance when submitted to the specific tests listed in this standard. This includes the vertical flame test, which is conducted on unwashed fabric and then again on fabric that has been home-laundered 25 times.

It requires a maximum Char length of no more than 6 in and a maximum of 2 seconds after flame. Another key test listed in this standard is determining the Fabric’s Arc rating, which in most cases is the arc thermal performance value.

Other tests referenced in this standard include tear strength seam slippage, color fastness, and shrinkage, to name a few.

Garment specifications are also outlined in ASTM F1506 including whether a manufacturer can track the Garment to the role of fabric it came from and if it is labeled with specific information.

ASTM F1506 sets some basic guidelines for clothing when you’re looking to protect your workers from arc flash hazards. Now, we have a standard called NFPA 2112 on the flash fireside.

NFPA 2112 Flash Fireside

The NFPA 2112 is the standard performance specification for flame-resistant garments to protect industrial Personnel against Flash Fires.

Like ASM F1506, this standard specifies the minimum performance requirements for flame-resistant fabrics and components. It also outlines design requirements for garments, addressing both the fabric individually and the Garment as a whole.

Some folks may only look to see that a fabric is certified to NFPA 2112, but there are advantages to having a garment certified as well. Not many manufacturers do all the work to certify their garments to NFPA 2112.

The fabric tests in this standard also include the vertical flame test, but it’s a little different. Fabrics need to be tested now and again after 100 Industrial launderings. This is more washings than ASTM F1506, which specifies 25 home launderings.

 

The maximum charge length allowed to pass the test is 4 in, and the maximum after-flame is 2 seconds. NFPA 2112 includes additional tests, including the ASTM F1930, commonly called “The Manikin Test.”

This test estimates the potential body burn injury in a given garment when exposed to a simulated flash fire. The thermal protective performance or TPP test helps measure the Fabric’s ability to block convective and radiant heat energy.

It also lists the oven test used to measure thermal shrinkage and ensure that garment components like reflective striping, zippers, and buttons don’t melt or drip.

ASTM F 1930 Flash Fire Protection

The other key test for fabrics used for flash fire protection is ASTM F 1930, the instrumented Manikin test. In this test, a standardized cover made from the fabric is placed on a unique Manikin with multiple sensors that measure the heat transfer through the fabric.

The mannequin is surrounded by burners set to generate two calories of thermal energy and is exposed for three seconds.

The sensor data then undergoes calculations to determine the estimated area of the body that would have received second or third-degree burn injuries. The hands and feet are not measured, and the head is measured but is not covered during the test.

So it always shows second or third-degree burn injuries accounting for 7% of a calculated body burn. The fabric passes if the total body burn percentage is less than 50%.

ASTM F 1959 ARC – Flash Protection

For fabrics used for arc flash protection, the key test is ASTM F 1959, which determines the material’s arc rating. For this test, three fabric samples are placed over sensors and holders surrounding a mechanism that generates an arc flash.

Multiple arc flashes are generated at various energy levels to calculate the point at which the energy passing through the fabric has a 50% probability of developing a second-degree burn injury.

Once that point has been established, the calories of energy generated are the arc rating or arc thermal performance value, also known as the ATPV. There may be a situation where the fabric breaks open before the ATPV has been reached.

 

If that happens, the testing is complete, and the calories generated at that point are considered the arc rating. In this case, it is labeled as EBT, not ATV. EP T stands for energy break open threshold.

Relation between ASTM D6413, ASTM F1506 & NFPA 2112

So, in review, the basic entry test, ASTM D6413, or the vertical flame test are used to determine if a fabric is flame resistant.

In their criteria, standards that reference the vertical flame test are NFPA 2112 on the flash fireside and ASTM F1506 on the electric arc flash side. Both standards outline the essential criteria for fabric and garments for protecting workers against these hazards.

NFPA 2112 requires a Char length of no more than four inches, and ASTM F1506 requires a Char length of no more than six inches. Both standards require that the after-flame last no longer than two seconds.

If a fabric fails to meet one of these requirements, it is not considered flame-resistant, and no further testing is performed.

Why Flame Retardant Fabrics are Important?

Using flame-retardant fabrics is essential to the contract curtain and soft-vanishing industry. In the UK, there is a strict regulation that all soft furnishings used in public must be flame-retardant.

The regulations are set out by Consumer Product Safety Commission (CPSC) standards and the Flammable Fabrics Act (FFA) organizations.

If the curtains and soft furnishings are not fire resistant, the supplier will face legal issues, be banned, or shut down his service in the UK.

The fabric does not burst into flames and is not transferred to other things in the room. Instead, it is much less likely to catch light in the first place. If it should burn, it will burn slowly and, in some cases, self-extinguish.

Non-Fire Retardant Fabric Swatch Test

Here, we are burning a non-fire retardant fabric swatch. As you can see, it quickly caught fire from the candle, and the flames traveled up the material, consuming it.

 

Fire Retardant Fabric Swatch Test

We then tried again with a fair atomic fabric swatch. The fabric did catch a light from the candle, but instead of burning, it melted away and shredded until the flames were extinguished.

 

How Flame Retardant Testing Affects the Durability and Safety of Fabrics?

Flame retardant testing plays an important role in ensuring the durability and safety of fabrics used in textiles, automotive, aerospace, and protective clothing. FR testing determines how a fabric resists ignition, reduces the flame spread, and self-extinguishes.

Regular fabrics are chemically treated to make FR. However, UV effects and multiple washes reduce the fabrics’ flame retardancy. Fabrics with inherently FR properties that retain their finish after multiple washes are considered more durable and safe.

Top Flame Retardant Fabrics for Fire Safety

The fabrics have two categories.

Inherently FR Fabrics

1. Aramid (Kevlar, Nomex)
2. Modacrylic
3. PBI (Polybenzimidazole)
4. PANOX (Oxidized Polyacrylonitrile)
5. Melamine
6. Basofil
7. Wool
8. Glass Fiber (Fiberglass)
9. Carbon Fiber
10. Silica Fiber

Chemically Treated Fr Fabrics

1. FR Cotton
2. FR Cotton Blends (Cotton / Nylon, Cotton / Polyester)
3. FR Rayon
4. FR Polyester
5. FR Acrylic
6. FR Viscose
7. FR Wool Blends
8. FR Nylon

Testing & Application

FR fabrics are used in various industrial sectors for the protection of workers. Firefighters use Nomex and FBI fabric to protect themselves from thermal heat. The cotton-treated fabrics are used in the gas, oil, and electric sectors to prevent heat with comfort.

Why Is Flame Retardant Testing Important for Children’s Clothing? 

Flame retardant testing is essential for children’s clothing because their bodies are more vulnerable to burn injuries. Consumer Product Safety Commission (CPSC) standards and the Flammable Fabrics Act (FFA) outline the sleepwear requirements for 9 to 14-month-old children.

The FR fabrics testing standards are ASTM D6413 and 16 CFR Part 1615/1616, which are used to determine the flame retardancy of children’s sleepwear. Inherently, FR materials are used in children’s clothing to protect babies from injuries in case of fire.

How to Pass Flame Retardant Testing for Textiles?

Passing of flame retardant testing depends upon meeting the compliance of ASTM D 6413, ASTM F1506, NFPA 2112, and NFPA 701 & ISO 11612.

Common Pitfalls

The FR fabrics fail to pass the FR standards due to improper chemical treatment application, prolonged exposure to UV radiation, several numbers of washes, excessive shrinkage, fabric degradation, and improper fiber selection.

Solutions

The FR failed testing can be avoided by the inherent flame retardant fibers in the fabric and correctly applying chemical treatment that can withstand several laundering washes. To resolve any issues, the fabric quality should be ensured by pr-testing before shipment.

The Future of Flame Retardant Testing

The future of flame retardant testing is advancing due to strict regulation, the development of eco-friendly flame retardants, and the latest methodologies for creating fabrics with comfort and flame retardancy.

Emerging Trends in Textile Safety

To reduce the toxicity risks of flame retardants regarding health and environmental issues, brominated and halogenated flame retardants are now replaced with safe phosphorus-based, silica-based, and bio-based FR coatings.

 Conclusion

Flame retardant testing for textiles is essential for user safety and international compliance. Flame resistance testing involves exposing a fabric to flame to determine its extinguishing behavior, resistance to fire, and char length in case of fabric damage.

Some techniques are used to measure the performance of FR clothing. The most basic test is the ASTM D 64 13 flammability test, also known as the vertical flame test.

Passing flame retardant testing depends on meeting the compliance requirements of ASTM D 6413, ASTM F1506, NFPA 2112, NFPA 701, and ISO 11612.

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