Use of Flame Retardants in Furniture and Textiles

Upholstered furniture is made of three parts (cover fabrics, upholstery and interliner) and some of these products smoulder and lead to the start of a fire. Synthetic fibres may burn fiercely and any already burning residue, may drip, carrying flames to other surfaces. Foams, which are not treated by fire retardants, ignite easily and will burn if the material is in contact with a flame.
There are several textile fibres available, which do not burn because of their intrinsic fire reaction properties.

Acting as a barrier between flame and foam or by limiting oxygen supply to fire, flame retardants can ensure an appropriate fire safety level for several natural and synthetic fibres.
Application can be made at the time of manufacture through the impregnation of end products by pulverization or backcoating.

Flame retardants are also be incorporated into the cover fabrics, upholstery or/and interliner, and in this case linked to the matrix, forming a new chemical product.

Unfortunately in many parts of Europe, there are not the stringent fire safety regulations in place as for the UK and Ireland, where the upholstered furniture safety regulation was introduced in 1980; followed by the ‘Furniture and Furnishings (Fire) (Safety) Regulations’ 1988. These have clearly resulted in the saving of many lives.

The regulations are applied to upholstered seating sold commercially and stipulate that the specification BS5852 must be met – which includes both ignitability testing for the upholstery and covering materials, and polyurethane foams in slab or cushion form.

There is currently much pressure from stakeholders to ensure that these regulations are passed throughout Europe. (see footage below)

Are you sitting comfortably ? (video)

Foams for upholstery and mattresses

Foams used as stuffing require good fire performance.
Stuffing is mainly containing polyurethane (polyesther or polyether) or latex foams which are ‘open-cell’ in their formation with interconnecting pores (for comfort and flexibility), but the bubbles of air allow ‘burn through’ and increase flammability. (see Flame Retardants- How do they Work?)

Flexible polyurethane foams are usually made flame retardant with additive compounds which act to increase the foam ignition temperature and reduce the rate of flame spread.

Various flame retardant compounds from the chlorinated phosphate ester family, (the presence of both chlorine and phosphorus in these products is advantageous for flame retardancy, working in both the solid and gaseous phase) are used in combination with nitrogen-based compounds such as melamine salts.

The main phosphate esters are:

• Tris(monochloropropyl) phosphate (TMCP or TCPP),
• Tris (dichloropropyl) Phosphate (TDCPP)
• Bis(chloromethyl) trimethylenebis(bis(chloromethyl) phosphate (BTMCP or V6).

During the burning of the material containing a phosphorous based flame retardant, phosphorus is converted into phosphoric acid which extracts water from the pyrolising substrate causing it to char. This results in a protective layer that shields the combustible material from the gas phase. Without the fuel the combustion is stopped.

With halogenated phosphorous flame retardants, chlorine or bromine traps free radicals in the gas phase that promote the degradation and the flame spread.

Melamine offers an excellent resistence to ignition from an external source.
On contact with heat it decomposes, acting as a heat sink and in doing so, it releases nitrogen which dilutes both oxygen and combustible gases. It also contributes to char formation, thus acting in both the gaseous and solid phases.

The flame retarded polyurethane foams, also called “fire modified” foams, are often characterized as CMHR (combustion-modified high resilience) where they contain a combination of melamine and with TCPP-LO (Tris(1-chloro-2-propyl) phosphate) achieving various classifications within British Standard specifications.

To reduce the quantity of flame retardant used and improve the foam properties, a combination of bromine with TCPP can be used to meet the British Standard test.

Tribromoneopentyl alcohol (TBNPA) is a reactive brominated flame retardant, combining high bromine content with very high stability. It is often used in combination with TCPP for polyurethanes where its high solubility in the system makes it especially useful. However, the higher costs mean that it is a solution used less frequently.

Fire proofing fabrics

- Fireproofing of cotton
  The principal agents used for cottons are brominated flame retardants and phosphorate compounds coupled in synergy with nitrogen derivatives. These are often used as backcoating for cotton, polyesther, acrylics, leather and artificial leather. Most of the time, these flame retardants are not durable over time.

- Fireproofing of wool
  According to the type of application, wool is used in combination with another fibre such as polyamide ; polyester ; or polyacrylic. The major compound is the wool, associated with another fibre in proportions varying from 15 to 20 % by weight. Several levels of fireproofing are found for the mixes described

- For the fire proofing of synthetic fibres, Halogen compounds can be used such as polyethylene terephthalate and acrylic resins. It should be noticed that chlorinated synthetic fibres, coming from halogenated monomers, have an intrinsic fireproof characteristic and do not need any chemical modification.

Durability

To remain effective, a flame retardant must stay in the treated textile throughout the product’s life. Depending on intended uses, it must not be released into the environment or be washed out i.e. when the textile is put in the washing machine, dry-cleaned, wiped, subject to humid conditions or weathering.

This also ensures that consumers and users of products are minimally exposed to the flame retardants used in textiles, because these are not released from the textile.

Durability of textile fire safety can be achieved in several ways:

• The chemical reacts with itself and is modified inside the fibres to make it more difficult to wash out. This requires special conditions to bring about the reaction. The THPC system uses ammonia gas catalysis on special equipment. It is most suited to cellulose/cotton textiles. This type of treatment will be durable to dry cleaning.
• The flame retardant reacts with the fibre to resist washing out. The DMPPA system requires conditions of acid reaction at elevated temperatures to achieve durable results on cellulose/cotton. This type of treatment will be durable to dry cleaning.
• The flame retardant is part of the synthetic textile itself which have been reacted with substances to produce an intrinsically flame retardant polyester textile.
• The flame retardant is insoluble and is bound to the fibres with a film forming polymer or “binder”. The durability is determined by the amount and type of binder used. The more insoluble the flame retardants the better the durability.
• The Deca BDE/Antimony trioxide system is typical.  All types of fibres including synthetic fibres can be treated using a back coating.
• The flame retardant has a suitable physical form and when synthetic fibres are heated to temperatures that allow the structure of the fibre to temporarily open the flame retardant can effectively dissolve in the fibre. The organic phosphonates on polyester fibre are an example of the method. Wash durable effects are possible.

Fire safety of clothing and children’s sleepwear

Because clothing is necessarily close to the body, cannot easily be removed, and can catch fire easily from contact with everyday lighted flame (e.g. candles), textile fire safety is a serious issue: “Clothing fires must be avoided because burn injuries are often severe, disfiguring, and can cause death”^[1].

Many tests have demonstrated the fire dangers of clothing textiles, for example the Norwegian Institute for Consumer Affairs study^[2] for the European Commission in 2004 and The Austrian Consumer Council^[3] website shows, with photos, how clothes “can burst into full flames within seconds”.
Estimates based on UK figures (before UK legislation) ^[4] suggest that there are some 6,000 clothing fire accidents per year in the European Union, of which 41% are fatal or involve severe burns. Regulations in the UK since 1987 ^[5] require children’s sleepwear to either burn slowly, or carry warning labels.

Loose fitting children’s sleepwear can present a real danger of serious fire injury^{[6] [7] [8]}, with accidental ignition possible from smokers’ materials, candles, cookers, fires and heaters. Snug fitting sleepwear does not burn so readily, because of reduced air pockets between the textile and body ; but increasingly children sleep in loose garments, including T-shirts. Safety-labelling of children’s clothes and flame retarded loose fitting sleepwear are both necessary to save children’s lives and injuries from fire.

1« Facts about fabric flammability », Prepared by Jan Stone, extension textiles and clothing specialist, and Sara Kadolph, professor, textile and clothing department, Iowa State University.

2 SIFO – Norwegian Institute for Consumer Research “Fire hazards of Clothing Related to Accidents and Consumer Habits” http://www.sifo.no/page/Publikasjoner//10081/49682.html?PHPSESSID=bd0554ecfdfa75dcf41d61b5d757d846

3 Austria Consumer Council, « Flammability of nightwear », 1998, with photos, http://www.verbraucherrat.at/pronightwearlong.html

4 http://www.dti.gov.uk/homesafetynetwork/cf_raccs.htm

5 UK Nightwear (Safety) Regulations 

6 National Association of State Fire Marshals “Comments on Standard for the Flammability of Clothing Textiles” 

7 Shriners Hospitals 2000

8 Victoria Dept. of Human Services : “Evidence-Based Health Promotion: No. 4 Child Injury Prevention”, September 2001 http://health.vic.gov.au/healthpromotion/downloads/child_injury.pdf

9 Stevens G.C., Mann A.H,  Risks and Benefits in the Use of Flame Retardants in Consumer Products, PRC07b/98/DTI CSU - DTI URN98/1026- January 1999