Kolcheva D. V.

Donetsk national university of economics and trade named after Mikhail Tugan-Baranovsky, Ukraine

Important factors of choosing and applying flame retardants for textile materials

Fabric flammability is an important textile issue, especially for stage drapery that will be used in a public space such as a school, theatre or special event venue. In the European countries, regulations require that textile materials used in such places should be certified as flame retardant. For textile materials and other fabrics used in public places, this is known as the NFPA 701 Test, which follows standards developed by the National Fire Protection Association (NFPA). Although all fabrics will burn, some are naturally more resistant to fire than others. Those that are more flammable can have their fire resistance drastically improved by treatment with flame retardant chemicals.

The choice of the flame retardants which are used for processing of textile materials for increasing fireproof properties is based on the chemical composition of the fibers, the required standard of performance and the available textile processing methods. In general, textiles from all fiber types can be satisfactorily made flame retardant by finishing. Fiber mixtures are more difficult, especially mixtures of synthetic fibers with cellulose or polyester with polyacrylonitrile. It is often not possible to produce durable results on mixed fiber fabrics. Many conditions affect the flame retardant of a fabric: how the fabric is used; what other fabric or non-fabric components are added to the base fabric; environmental conditions such as sunlight, dust, humidity, etc; length of time in service; sewing, printing, painting or any other added processing steps. 

Flame retardants can be applied for textile treatments by finishing methods, such as: padding, spraying, dipping and coating methods with special sophisticated equipment. The products are not generally substantive and therefore cannot be applied in the same way as dyestuffs. A relatively high amount of chemical must be applied to achieve suitable effects and this is not normally possible by exhaust methods.

Flame retardants, that dissolve in water, based on ammonium salts with a simple structure, at higher drying temperatures or through over-drying show a tendency to split off ammonia. The residual acid may cause damage to sensitive fibers and dyestuffs. As a result there can be yellowing of the fiber, change of dyed shade and redaction of durable characteristics of the textile materials. Ammonium containing salts should not be dried above 100ºC. Guanidine derivatives are clearly superior in thermal stability and can be dried at temperatures up to 160ºC.

Pigment flame retardants are stable at higher temperatures. Here the drying and curing conditions must be base on the conditions required by the binder and fibers involved.

Durable flame retardant finishes, enable fabrics to be washed and there can be dry-cleaning resistant effects by fixation to the fiber. Such finishes require the normal finishing conditions to be matched to the conditions necessary to obtain the required durability. Durable flame retardant effect in finishing textile materials may be achieved in the following ways:

· forming an insoluble polymer, from monomers, inside the structure of the textile substrate;

· forming a stable linkage between a substrate and a flame retardant;

· dissolving a flame retardant inside a substrate;

· coating the fibers or one surface of the textile materials with a flame retardant and a suitable binders.

Such variants can lead to fiber damage, compromised dyestuff fastness and influence the degree of durability achieved.

Flame retardant nature of textile materials is influenced by the fabric weight and whether the fabric is of woven, knitted or non-woven construction. Lightweight, open construction fabrics are normally more difficult to flame retard compared to heavy, dense structured fabrics. This is usually a question of oxygen supply to the burning process.

For the best flame retardant performance, the preparation of a fabric plays an important role. Residues of sizes and other auxiliaries such as coning oil, the residues of dyehouse chemicals, softeners etc. can have a negative influence on the light fastness, fabric handle and durability of a finish. In every case, a good absorbency in the substrate will assist in a good distribution of the flame retardant. Poor absorbency can lead to the finish concentrating at the surface of the textile and worse flame retardant effects, fabric handle and a tendency to show 'chalking' or other surface disruption.

The flame retardant properties of a textile material and its ability to fulfil the requirements of a performance standard are dependant on an understanding of the required flame retardant deposit level. Without the application of sufficient flame retardant, the textile will not show the required levels of performance in terms of rate or spreading burning, or after flaming. It is recommended that each fabric should be assessed for required add-on level of flame retardant in prior tests according to the required test performance. The manufacturers recommended minimum add-on level is only a starting point. Over application of flame retardant can lead to an adverse effect on handle without, improving the flame retardant effects.

The possible effects on other textile characteristics such as Light and Rub Fastness and Tear Strength must be considered. When considering the wide variation in the nature of textiles with regard to factors such as fabric processing, dyestuff selection, end-use demands, and to avoid possible future problems, it is necessary to make the fullest possible evaluation of product application in prior tests.

Every country has its own series of standards or test and these may often be similar but always different. The process of harmonizing these standards will eventually simplify this situation. In General, for textile materials that are used in public buildings, trains, boats, planes, automotive flame retardant performance requirements have usually, already been established.

Flame Retardant Finishing is often a requirement in addition to other finish requirements and combined finishes different effects, which come from the use of other finishes. In addition to simple questions of the compatibility of different components in an application bath, the effects on the required performance must also be checked, especially as they may involve a negative influence on flame retardant properties.

Nowadays increasing fireproof properties of textile materials processed by flame retardants is an important stage of ensuring safety in places of mass gathering of people. Principles of choosing flame retardant for textile materials in terms of a chemical composition of fibers, suitable methods of applying flame retardants of textile materials, durable effect and properties of flame retardants are shown. Textile materials finished by flame retardants must meet safety demands and show necessary results in flammability tests.