Textile industry: Novel flame retardant systems point to the future

Cutting the Economic and Human Cost of Fire. By Dr Ian Holme (source: World Textile Information Network (WTiN))

It has been reported that the 7-8 million fires each year in the industrialised nations claim the lives of some 70,000 – 80,000 people, with another 500,000 – 800,000 suffering injury.1 Most people die in fires in homes, buildings and transportation, and the fire victims die as a result of toxic gases (50%), burns (25%), toxic gases and burns (20%), as well as from cases that are unclear (5%).

Fires cost around 1% of the gross national product of the industrialised nations, with around two-thirds of this amount being spent on fire-preventative measures and the remaining one-third on the losses from the fire.

Flame retardants save lives and protect property from damage, but increasingly the flame-retardant manufacturers are under pressure to phase out well-established products and introduce novel flame retardants with enhanced ecotoxicological properties for all types of materials, including textiles.

The incorporation of flame retardants into textile materials is particularly important in upholstered furniture, but the markets for flame retardants are increasing. The main end-use applications for flame retardants currently include:

home textiles: curtains, blinds, upholstery fabrics, carpets and mattress ticking

technical textiles: seat coverings and carpets for cars, rail vehicles and aircraft

functional textiles: industrial protective clothing, eg. firemen, welders, metalworkers and workers in the petroleum industry

military textiles: uniforms, backpacks and tents

In upholstered furniture the use of flame retardants can potentially give rise to different risks, such as:

• exposure to flame retardants during manufacture of the product (worker acute and chronic toxicity)

• exposure to flame retardants under normal living conditions. This risk mainly results from the accumulation of release flame retardants in indoor air via inhalation and/or skin contact and migration of substances (chronic toxicity)

• the environmental risk during recycling or incineration of the products (mainly ecotoxicity)

• the risk of increasing the emissions of toxic gases from accidental fires due to cigarettes or matches on upholstered furniture (acute toxicity)

The flame retardants for textiles operate by a variety of different chemical mechanisms. Thus, inorganic and organic phosphorusbased flame retardants dehydrate the fibres, leading to the production of a black carbonaceous char. Nitrogen-based flame retardants are often used in combination with phosphorusbased flame retardants, which can lead to crosslinking that supports the carbonisation process. Halogen-based flame retardants generally interfere with the free-radical reactions in the gaseous phase, slowing down the reactions that lead to heat generation. Intumescent systems utilise an acid catalyst, a carbon-rich source and a spumific (blowing agent) to form a protective heat-insulative and carbon-rich foam layer, which is expanded by the blowing agent to provide a thick, carbon-rich barrier to heat, oxygen and flame.

Flame-retardant coatings for textile fabrics often rely upon the use of antimony trioxide and a halogen-based flame retardant such as DecaBDE (decabromodiphenyl ether). DecaBDE has been extensively studied over a long number of years and the Risk Assessment Report compiled over a period of 10 years by the European Union concluded that DecaBDE does not pose a risk to the environment or human health. Nevertheless, the US Environmental Protection Agency (EPA) has supported and encouraged the voluntary phase-out of the manufacture and importation of commercial versions of DecaBDE and has received commitments from the principal manufacturers and importers to initiate reductions in the manufacture, import and sales of DecaBDE in the USA. This started in 2010, with all sales to cease by December 31, 2013.

In addition, the UK REACH Competent Authority is considering the listing of DecaBDE as a substance of very high concern (SVHC). This is based upon fears expressed by the UK Health & Safety Executive and Environment Agency that DecaBDE might degrade to lower polybrominated diphenyl ether (PBDE) congeners, meeting the PBT (Persistent, Bioaccumulative and Toxic) criteria.

However the BSEF (Bromine, Science & Environmental Forum) has asserted that degradation was minimal and posed no serious risk to the environment. The industry needed an SVHC classification that was based solely on science and not on emotional arguments or reputation, otherwise this would remove a chemical substance of high value to society without due scientific process.

Against this background of debate, new flame-retardant chemicals are emerging, with product developments focused upon:

• polymeric solutions: large molecules

• reactive products that can become bound to the final polymer

• non-toxic, non bioaccumulative molecules

• mineral products

• life-cycle performance and carbon footprint.

In addition, the flame retardants must also be non-PBT (persistent, bioaccumulative, toxic) and non-CMR (carcinogen, mutagen, reprotoxic), be durable (non-leaching) and insoluble and non-hydrolysable. Preferably, the flame retardant should be used at a decreased total loading and enable a lower antimony trioxide (ATO) loading to be used.

Albemarle has introduced Saytex 8010, which is based upon ethylene 1,2 bis(pentabromophenyl) (EBP).4 Saytex 8010 is claimed to be the most widely applicable alternative to DecaBDE, with enhanced thermal stability, non-blooming properties, UV stability for colour applications and also recyclability. Saytex 8010 is available in powder or pellet form, is EU RoHS-compliant and meets European dioxin ordinances. It has also been shown to be safe for human health and the environment.

Another new product from Albemarle is a polymeric flame retardant, Green Armor. This is claimed to be the first in a family of sustainable solutions, Green Armor being non-bioaccumulative and non-toxic for mammals and the environment.

The Great Lakes Solutions division of Chemtura has introduced Emerald Innovation 1000 as an effective replacement for DecaBDE and decabromodiphenyl ethane. It is designed to be used as a replacement in polyolefin and styrenic-resin systems and can be easily substituted into existing production technologies, such as textile backcoating, with minimal adjustments. It maintains comparable fire-safety performance with similar load levels to other high-efficiency brominated flame retardants.

ICL-IP has introduced TexFRon as a replacement for DecaBDE and hexabromocyclododecane (HBCD). It is applied via backcoating to polyester and polyester/cotton blends. With a solids content up to 65%, it offers 10-15% better efficiency compared with DecaBDE and is durable to washing. TexFRon 9020 is also durable and applicable via backcoating and offers 30-50% better efficiency over DecaBDE. In addition, the ATO loading can be decreased by 50-70%.

TexFRon is based upon pentabromobenzyl acrylate. Thus the bromine is chemically bound into the polymer backbone, offering wash durability to 50 cycles on polyester/cotton. Both TexFRon P and TexFRon P+ are applicable by backcoating, the latter offering improved efficiency over the former. TexFRon P+ offers a reduction of 40% in bromine loading and 70% in ATO loading, giving excellent low-smouldering performance and wash durability to 20 cycles.

Clariant has introduced the newgeneration flame-retardant Pekoflam ECO/ SYN system, hailing it as a fundamental breakthrough in durable flame-retardant finishes. This innovative bicomponent system, based upon Pekoflam ECO and Pekoflam SYN, is designed for application on existing equipment and is free of any SVHC2- restricted chemicals and free of Oeko-Tex restricted materials.

ECO stands for ecological and economic and SYN for synergy. The new bicomponent flame-retardant system from Clariant has a low impact upon fabric strength, no formaldehyde emissions, and offers excellent wash fastness in domestic washing, as well as good performance in industrial applications. Processing can be conducted on common finishing lines with high-temperature curing and a suitable wash range.

Clariant has also introduced a powderbased flame retardant, Pekoflam HFC, designed for application via coating technology. This utilises organic phosphinate compounds as a substitute for halogenbased systems. This non-halogenated coating system decreases smoke emissions to provide high flame-retardant performance on upholstery and carpeting containing synthetic fibres and blends. Compared with other phosphorus-based powder flame retardants, Pekoflam HFC offers better binder compatibility and a lower impact on the rheological behaviour, which can be increased in the presence of phosphorus-based flame retardants.

Huntsman Textile Effects has introduced Pyrovatex EXP, a durable-flame retardant finish for 100% polyester, which can be applied on white and pale-shade fabrics. Applicable via exhaust methods, it is normally applied at pH 4.5-6.0, using Pyrovatex EXP PLUS accelerator and acetic acid at 90°C for 15 minutes, followed by a wash-off treatment. Pad application is normally followed by drying at 100-120°C. While a curing step is not necessary to obtain durability, curing at 150°C is necessary on automotive fabrics in order to pass the fogging requirements. For dark shades a top finish is recommended, to improve the rub fastness and thermomigration performance. Pyrovatex EXP has a little/ negligible influence on light fastness and a negligible influence on handle.

Avocet Dye & Chemical Company (Brighouse, UK) has introduced Cetaflam DB EXL, which is a halogen-free, antimony-free and solvent-free durable flame retardant that is REACH-compliant and suitable for use with fluorescent brightening agents and fluorescent dyestuffs. Compared with a conventional pad application, Avocet claims that Cetaflam DB EXL – which is applied via an exhaust procedure – saves up to 40% on processing time, energy and resources, enabling the production of sustainable textiles. Designed for use on polyester fabrics, Cetaflam DB EXL is suitable for application to automotive, domestic and contract upholstery, masstransit fabrics, workwear and tents. Cetaflam DB EXL does not require curing, so that there is no risk of shade change or loss of colour fastness and this low-environment-impact system generates no toxic effluent.

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