Flame resistant fibres

In 1962 Courtaulds announced a flame-resisting fibre BHS said to be a 50 50 vinylidene chloride-acrylonitrile copolymer. This product has subsequently been renamed Teklan . 

Yet another heat- and flame-resistant fibre is the Bayer product AFT-20(X). This is classed as a polyquinazolinedione and contains the structural element in Figure 18.34. 

Van den Heuvel CJM and Klop EA, High-Performance Fibers - A Bird s eye View of their Structure, Properties and Applications", paper presented at the "9th Twaron Symposium", Konigswinter, Germany, 24/25 April, 2002. Van Krevelen DW, "New Developments in the Field of Flame-Resistant Fibres", Angew Makromol Chem 22 (1972) 133-158. 

This group is perhaps the most well known and exploited of all the inherently heat and flame resistant fibres developed since 1960 and all members of this group are typified by having thermal resistances in excess of 300 °C for short-term exposures and high levels of inherent flame resistance (see Tables 8.1 and 8.4). Because of their aromatic polymeric structures, they possess quite low H/C ratios <1 (see section 8.2) and so release few potentially flammable volatiles, reflected in their high LOI values of 29 vol% or greater (see Tables 8.1 and 8.4). 

This group is perhaps the best known and exploited of all the inherently heat and flame resistant fibres developed since 1960, and all members of this group are typified by having thermal resistances in excess of 300°C for short-term exposures and high levels of inherent flame resistance (see Table 4.2). 

Although the majority of flame-resistant fibres are produced from fully aromatic and/or heterocyclic polymers, an alternative approach, based on utilization of crosslinked polymers, is also feasible. Phenol-formaldehyde fibres were produced by a process involving spinning of a fusible novolac resin followed by crosslinking of the precursor fibre. A recently developed nonflammable fibre with a low smoke-evolution is based on a copolymer of acrylic acid and acrylamide the carboxylic groups are crosslinked by zinc ions. ... 

Most flame-retardant finished textiles are excluded from the Oko-Tex Standard 100 label. In all cases, the durability of the finish is often a problem. It is the responsibility of the fabric finisher to address these issues if commercial flame-retardant fabrics are to be produced. An alternative for the fabric designer without most of the named problems is the use of flame-resistant modified fibres, but... 

The modacrylic fibres have similar properties to those of acrylics and are flame resistant..Mostly this fibre is based on a 60/40 or 50/50 copolymer of acrylonitrile with vinylidine chloride (CH = CCy together with small proportion of ternary monomer to improve ionic dyeability or hydrophilicity. The better known modacrylic fibres have a ribbon-shaped or pea-nut shaped cross-section. One problem encountered with modacrylic fibre is loss of lustre at the boil [83, 84]. This fibre is used for apparel, home furnishing, wigs etc. 

Some three decades ago, scientists from the Du Pont company developed polycondensation methods which allowed the preparation of high molecular weight wholly aromatic polyamides. The first commercially produced wholly aromatic polyamide fibre was poly(m-phenyleneisophthalamide) (Nomex, Du Pont, 1967) [la, c]. Some years later, development of the preparation and processing of poly(p-phenyleneterephthalamide) (PPTA) led to the commercialization of the para product Kevlar (Du Pont) in the early seventies [lb, c]. While Nomex shows excellent thermal stability and flame-retardance, and indeed is referred to as a heat and flame resistant aramid fibre, Kevlar fibre also has similar properties, but in addition it has exceptional tensile strength and modulus, and is referred to as an ultra-high strength, high modulus aramid fibre. 

Flame retardant finish for technical wool fabrics. Within the technical textile sector, wool textiles requiring high levels of heat and flame resistance are limited in the main to the contract and transport furnishing fabric and protective clothing markets. The non-thermoplastic and char-forming characteristics of wool, coupled with an inherently quite high level of low flanunabiUty, make it an ideal fibre when handle, comfort, and aesthetics are also required. 

All fibres described in this chapter are used iu textiles which must achieve acceptable levels of heat and/or flame resistance as determined by national and international standards which are usually deliued iu regulations and/or legislation. It is beyond the scope of this chapter to describe the many and varied textile heat, flame, and fire testing methods but receut treatments of this complex subjecT have been published and mention is made of seme in Chapters 9, 10, and 11. Generally, heat and flame resistance tests for technical textiles are required for the following application areas where national and/or international regulations exist... 

Burrow T. Flame resistant man-made ceUnlosic fibres. In Selcen Kilinc F, editor. Handbook of fire resistant textiles. Cambridge Woodhead Publishing 2013. p. 221 44. 

Fibre choices for thermal protective clothing include inherently flame resistant (FR) fibres such as the meta- and para-aramids, polyamide-imide, polybenzimidazole, modacrylic and chemically modified fibres such as viscose and modal, polyester, and nylon, as well as FR treated or finished cotton and wooP"" (see also Chapter 8). The... 

Mentioned above is the requirement for some defined level of fire resistance for fibres and assemblies used in most transport sectors to be determined more often than not by national or international regulations that govern their performance requirements. As mentioned above, cars are included because those textile components in internal passenger compartments only such as seating, carpet, seat belts, and internal side and roof lining fabrics require a defined level of flame resistance. 

Part 5 is relevant to floor coverings since these are required to have a surface with low flame spread characteristics and are tested in accordance with Resolution A.653(16). This defines a method of determining surface heat spread in a vertical orientation under a heat flux of 49.5 kWm" at the initial part of the sample length reducing to 1.5kWm- after 740 mm. Thus carpet fabrics must have higher flame resistance than normally expected for such a horizontally orientated textile. Consequently, flame retarded wool (e.g. Zirpro -treated wool see Chapter 8) will feature as an important fibre in appropriate woven or tufted stractures which combine both the necessary aesthetic and technical requirements. 

Fabrics should be tested after a defined wash or durability test which, in the case of Part 7, for fabrics treated with a flame retardant, is a single specified wash cycle. Only so-called durable flame retardant finishes as described in Chapter 8 will pass such a wash cycle since semi-durable treatments are usually only resistant to dry cleaning or simple water soak tests specified in BS 5651 1989, for example. Fabrics containing inherently flame retardant fibres such as Hi-modified polyester (e.g. Trevira CS ), polyacrylics (e.g. modacryUcs such as Kanekaron ), and polypropylene do not require a prewash treatment prior to testing. 

---