Contract Textile International

Flame Retardance of Home Textiles

Volume 2 / May-August 2010

GÜLAY ÖZCAN
Istanbul Technical University. Department of Textile Engineering, Gumussuyu-Taksim-IST, Turkey

Abstract

Safety concern has become a driving force in developing products for the home textiles. Today in the textile business, concern for personal safety, health, and the environment now overshadow the consumer's fear of dirt and stains. This awareness has led to new standards and legislation directed to reducing the risk of fires, particularly with respect to upholstery and upholstered articles. Today 65% of all domestic fires are caused by the direct or indirect ignition of textiles. In order to obtain flame retardance for these products different FR techniques are applied to plastics or textiles to slow down the burning process, reduce heat, and prevent emission of toxic gasses are increasing in number and improving in quality.

 Introduction

At the head of the protectiveness features expected from home textile products is protection against high heat and burning. Burning is an exothermic reaction, it propagates fast by feeding itself with the high heat and suffocating and poison gasses it generates. High heat produced during burning brings adjoining material to the ignition temperature and initiates their burning, thereby fueling the fire.
Among textile materials the one that is inflamed first and burns most easily is clothing fabrics; then come furniture filling and bedding material, upholstery fabrics, sheers and drapes, and other decorative fabrics. The main sources of heat in fires related with home textiles are cigarettes and matches. Generally, the main sources of heat in bedding fires are sparks and cigarette burns, in sheer and drape fires open flames and electricity leakages, and in carpet and kilim fires; electricity leakage-short circuits or open flame contact.
The most important way of burning in home textile materials is smoldering. This carries utmost importance for especially bed, pillow, and furniture filling material; it results in sudden ignition and the growth of fire instantly. The majority of fatal home fires are caused by this and effect comprises 25% of all textile fires. Fires caused by the ignition of upholstery fabric comprise 20% of total textile fires, and 66% of fatal fires. Fires cased by the ignition of sheers and drapes comprise 5% of all textile fires and 3% of these; end in fatalities while 4% end with injuries.
A combination of a fabric cover and a polyurethane filling, as for example in furniture, can result in the propagation of a smoulder in the polyurethane as well as through the cover material. Inward progress of the smouldering pyrolysis zone was generally dependent upon energy supplied from the surface. The smoulder wave in the foam is slow (-10.' mdsec) and that peak smoulder wave temperature was of the order of 350°C to 450°C. These temperature values would have been exceeded (600°C) in the smouldering cellulosic material that covered the foam and it is likely that the foam in isolation generated insufficient heat to allow a smoulder to propagate. The illustration of the foam/fabric interaction in the smouldering process is shown in the figure 1.

 
Figure 1. Foam/fabric interaction in the smouldering process. After a diagram by McCarter

The type of furniture that can be ignated by a cigarette; the conditions (such as position on a chair etc.,) under which this ignition will occur; and the time it takes, (if the smoulder develops) for the transition to flaming to occur from the time the cigarette was discarded. Table 1 shows that smouldering and burning behaviuor of six commercially upholstered chairs. It is clear that chairs are  smouldered and burst into flames when air is blown into the test chamber to purge the accumulated combustion products.

Table 1. Smoulder/burn behaviour of six upholstered chairs.

Mechanism of Fire Retardance

Flame retardants can act physically or chemically and sometimes both by physically and chemically interfering at particular stages of burning.
There are five different mechanisms in this field:

 1.Endothermic Degradation : Certain materials can break down endothermically when they are subjected to high temperatures. Magnesium and aluminium hydroxides are such examples. Various hydrates also act similarly. The reaction takes off heat from the surroundings, thus cooling the material.

2.Dilution of Fuel: Substances, which evolve inert gases on decomposition, dilute the fuel in the solid and gaseous phases. Inert fillers, eg. talc or calcium carbonate, act as diluents, lowering the combustible portion of the material, thus lowering the amount of heat per volume of material that it can produce while burning. Thus the concentrations of combustible gases fall under the ignition limit.

3.Thermal Shielding : A thermal insulation barrier is created between the burning and the yet-to-burn parts. Intumescent additives are sometimes applied that turn the polymer into a carbonized foam, resultantly separating the flame from the material and slowing down the heat transfer to the unburned fuel.

4.Dilution of Gas Phase : Inert gases, mostly carbon dioxide and water, act as diluent of the combustible gases, lowering their partial pressures and the partial pressure of oxygen, thus slowing the reaction rate. These gases are produced by thermal degradation of some materials.

5. Gas Phase Radical Quenching : Chlorinated and brominated materials undergo thermal degradation and release hydrogen chloride and hydrogen bromide. These react with the highly reactive H. and OH. radicals in the flame, resulting in an inactive molecule and a Cl. or Br. radical. The halogen radical has much lower energy than H. or OH. and thus has much lower potential to propagate the radical oxidation reactions of combustion. Antimony compounds tend to act in synergy with halogenated flame retardants. The HCl and HBr released during burning are highly corrosive, which has reliability implications for objects subjected to the released smoke.

6. Simultaneous Reactions: The much improved result obtained by using antimony oxide in combustion with chlorinated parrafins is an example of simultaneous gas and therma shielding phase. Thermal decomposition of the chlorinated products to give hydrogen chloride which further reacts with antimony oxide to give in situ formation of antimony chloride, results in a balnketing of flame propagation and also in chemical modification of the combustion reaction.

Recent progress in flame retardant technologies can be listed as

1. Nanometer flame retardant technology:
2. Microcapsule flame retardant technology:
3. Superfine melt technology:
4. Surface modification technology
5. Smoke abatement technology
6. Cross linkage technology
7. Macromolecule technology
These technologies have been developed to give fibers significant comfort and aesthetic characteristics along with their high protection characteristics.

Research has been ongoing for years to minimize burning incidents that cause great loss to life and property. As a result, important developments were achieved in the protective characteristics of sheers, drapes, upholstery fabrics, furniture filling material, barriers, and bedding material. Today, there are many flame retardant fabrics, fibers with flame retardant structure, composite barrier materials, and flame resist filling materials in the market.

In spite of the success of the flame retardant (FR) treatment processes in home textiles, usage of FR-fibers is increasing in popularity. Fabric structures where these fibers are used alone or mixed with natural FR-fibers allow protection of important textile quality characteristics. Currently, it is possible to produce flame retardant fabrics without changing the fabric properties, behavior, texture, and color quality. The most popular synthetic fibers used for this purpose are PVC fibers (Acethoclorin, Avisco, Avisco Vinion, Chlorin, Crinovyl, Rovyl, Thermovyl, Envilon, Leavil, Vmicelon, Movil, MP Faser, and Teviron) modacrylic fibers ( ynel, Flura, Kanecaron, Teklan, Verel, Creslan, and Velicren) and polyester fibers (such as Revira FR, Fidion FR). These fibers allow protection of significant comfort and aesthetic characteristics along with their high protection characteristics. Next to using FR fabrics, usage of FR back coatings, insulation, filling, and furniture structural materials in the composition of home furniture and textile products will of course prevent the growth and advance of fire significantly.
The barrier material to be used must protect its structure even after pyrolise, it must minimize heat transfer to the filling part of the furniture, and it must prevent oxygen transfer in order to stop the burning process. There are many materials used as barrier materials. Carbon fiber is the most popular of these. Back coating of upholstery fabrics usage of chemicals that provide polymer-based flame retardation, is quite popular, however, it is preferred less in home upholstery. Furniture and beds started passing modern flammability tests upon expedient usage of flame-blocking materials as barriers.
In the development of flame retardant materials, usage of light materials with heat insulation and flame-blockage that improve the comfort of the textile products without harming the protectiveness characteristics, are becoming popular. Composite materials are also used for this purpose.
All these solutions reached success when the public was made aware and were educated in developed countries, along with the developing thecnology and the need for protection on that developed in parallel.

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