Flame-retardant Fiber Research Articles

The flammability of Lyocell

This paper describes the work on the reaction between the solvent spun cellulose fibre, Lyocell, and N-hydroxymethyl phosphono proprionamide (Pyrovatex CP). The reaction between this latter compound and cotton is a well known method of producing a flame retardant fibre. However, it has been shown that, when used on Lyocell, only half the amount of this flame retardant will produce an equivalent degree of flame resistance. Further, by the appropriate choice of co-monomer, a flame retardant fibre can be produced which does not show the expected loss associated with the flame retardant.

Environmental consequences of using flame-retardant textiles—a simple life cycle analytical model

This paper extends earlier work which explored the possibility of undertaking a life cycle analysis of flame-retardant cotton and polyester textiles and consequently enabled semi-quantitative estimations of their relative environmental impacts to be made. This model is extended to undertake full environmental audits of a range of flame-retardant textiles and requires full consideration of each stage from fibre/raw material production to eventual disposal. The need for comprehensive data at all stages, however, demonstrates that comparisons between competing products are neither simple nor, at present, possible. Thus an environmental rank value is given to each stage in the manufacturing process and product life of each flame retardant fibre and derived textile. Summation of rank values enables an overall environmental index to be defined which may be used to compare the environmental impact of each generic type of currently available flame retardant, single fibre-containing textile. The results show that each of the eleven generic fibres analysed yield environmental index values within a range 32–51% where 100% denotes the worst environmental position possible. This relatively low range of values suggests that current production and processes which attempt to maximize economic viability also tend to reduce environmental impact. © 1997 John Wiley & Sons Ltd.

Environmental consequences of using flame‐retardant textiles—a simple life cycle analytical model

This paper extends earlier work which explored the possibility of undertaking a life cycle analysis of flame-retardant cotton and polyester textiles and consequently enabled semi-quantitative estimations of their relative environmental impacts to be made. This model is extended to undertake full environmental audits of a range of flame-retardant textiles and requires full consideration of each stage from fibre/raw material production to eventual disposal. The need for comprehensive data at all stages, however, demonstrates that comparisons between competing products are neither simple nor, at present, possible. Thus an environmental rank value is given to each stage in the manufacturing process and product life of each flame retardant fibre and derived textile. Summation of rank values enables an overall environmental index to be defined which may be used to compare the environmental impact of each generic type of currently available flame retardant, single fibre-containing textile. The results show that each of the eleven generic fibres analysed yield environmental index values within a range 32–51% where 100% denotes the worst environmental position possible. This relatively low range of values suggests that current production and processes which attempt to maximize economic viability also tend to reduce environmental impact. © 1997 John Wiley & Sons Ltd.

Novel Intumescent Applications to Textiles

Recently the use of intumescents that interact with flame retardant fibres during the application of heat to form a novel char structure showing unusually high flame and heat resistance has been reported [1]. The interactive pyrolytic mecha nisms of both components creates a char-bonded structure that is unusually resistant to oxidation. This paper extends the previous work to include flame retardant cotton; it studies the evidence of this interaction by thermo-analytical and scanning electron microscopic studies. The char formation characteristics and oxidative resistance ofthe composites have been studied by mass loss calorimetry at heat flux rates in the range 25-75 kW.m-2.

Evidence of interaction in flame-retardant fibre-intumescent combinations by thermal analytical techniques

Abstract Flame retardants when applied to cellulosic fibres, change their decomposition in such a way that significant conversion to carbonaceous char occurs. Intumescents, when dispersed on these flame-retardant (FR) fibres, enhance this property. They not only produce an expanded and thermally protective char barrier, but also interact with FR fibres to form a so-called char-bonded structure which has been shown to possess unusually high resistance to air oxidation at temperatures in excess of 500°C. The effectiveness of the char-bonded structure as a flame and heat barrier is considered to be dependent on the efficiency of the interaction of fibre and intumescent char-forming chemistries. Previous studies have demonstrated the interaction between various flame-retarded viscose fibres and phosphate-based intumescents; current research extends the work to include flame-retardant cottons. In this paper, these interactive properties are studied by using the thermal analytical techniques, TMA, TGA and DSC, which enable the various pyrolysis transitions and associated volatilisation and intumescent char-formations to be studied. In this way a greater understanding of the mechanism of complex char-formation and its subsequent oxidation may be investigated.

Complex char formation in flame-retarded fibre-intumescent combinations—II. Thermal analytical studies

It is well known that flame retardant fibres, when heated, decompose differently when compared to untreated ones and this is especially so for char-promoting flame-retarding species such as Lewis-acid generators in cellulosic fibres. Certain intumescent systems when dispersed about flame retardant fibres, interact and develop a unique ‘char-bonded’ structure which has been shown to enhance flame and heat resistant properties. These interactive fibre-intumescent combinations require that both the flame retardant fibre and intumescent form chars by chemically and physically compatible mechanisms, usually by a semi-liquid intermediate phase. Examples analyzed to date are flame retarded viscose fibres (Visil, Kemira; Lenzing FR Viscose) which although comprising different flame-retarding species, generate polyacids on heating. Intumescents based on ammonium polyphosphate behave in a similar way thus enabling physicochemical interactions of both charring components to occur. Initial studies of char structure using scanning electron microscopy have already shown evidence for this kind of interaction. In this paper, the mode of thermal degradation of these systems has been studied by thermal analysis (DSC, TGA) and the nature of char determined by IR studies. The results of these investigations are used to more fully understand the mechanisms involved.

A study of thermal stability of polyester containing phenyl phosphonate unit for flame retardant fiber

Phenyl phosphonic acid (PPA) was chosen as a comonomer to manufacture flame retardant polyester fiber. The yield based on PPA is less than 55% by a conventional polyester formation process. Different factors which might affect the yield of the copolymerization were investigated. The phosphorus residues in the reactor during the process of polymerization were monitored. It is found that the phosphorus residues decrease sharply in the high vacuum stage. This indicates that factors which increase the molecular weight of the prepolymer containing phenyl phosphonate unit will promote the yield of the copolymerization. In order to get an insight into the low yield of the copolymerization, the compounds containing phenyl phosphonate unit, bis(2-naphtholyloxyethyl) phosphonate (BNEP) and bis( p-methoxycarbonyl phenyl) phosphonate (BMPP) were synthesized for model studies. The preliminary results showed that these compounds decompose significantly above 240 °C. This suggests that the low yield of the PPA polymerization process may be attributed to the thermal instability of the OP bond in the phenyl phosphonate unit at the polymerization temperature.

難燃素材の現状

難燃素材の現状

The development of Trevira CS (comfort and safety)

In recent years the chemical and physical characteristics of polyester have enabled manufacturers to produce a wide range of speciality products. Of particular importance is the fibre's good resistance to ignition. Samuel Black outlines the reasons why Hoechst AG chose polyester in its attempts to develop a flame-retardant fibre.

Fire-retardant materials

Conventional materials (natural and man-made fibres, plastics, wood, paper etc.) used in everyday life are, in different degrees, liable to ignition. This fact has impelled the development of new materials which are inherently resistant to flame and heat or to modify these materials by using flame-retardant additives/treatments to meet the stringent regulations set for fire protection. This paper gives an overview of the newly developed inherently flame-retardant fibres and engineering plastics specifically aramids, polyimides, polybenzimidazole, novoloid, polyphenylene sulphide and carbon fibres. The use of various additives and FR finishes has also been highlighted.

Effects op Flame Retardant Cotton of Laundering with Bleach

Flame retardant cotton fabrics (Pyrovatex CP-treated) were subjected to laundering or soaking in hypochlorite bleach. The quantity of bleach and the method of bleaching are discussed with respect to changes in flammability as shown by trends in char length and elemental composition. Low concentrations of hypochlorite used for a short period of time (3.5 minutes) did not affect the flammability after 20 washes. High concentrations of hypochlorite used for a longer period of time (30 minutes) resulted in loss of flame retardancy after 6 washes. No morphological changes in the flame retardant fibers caused by the laundering and soaking were observed by scanning electron microscopy.

A blend for children's sleepwear incorporating inherently flame-retardant fiber

A blend for children's sleepwear incorporating inherently flame-retardant fiber

The effect of chemical and polymer finishing treatments on the flammability of fabrics for protective clothing

Finishing, in its widest sense, covers all processes which fabrics undergo after weaving or knitting. It is the responsibility of the finisher to remove processing oils and fibre lubricants, to colour the fabric, to develop the final appearance and handle, and to improve, where necessary, the performance characteristics of the fabric. In the simplest routine the fabric is scoured to remove oils and other impurities and to consolidate its structure, dyed or bleached, its surface fibres are removed by singeing or cutting, and then it is pressed. Some fabrics require special mechanical finishes such as calendering, embossing, milling, raising, or shrinking in order to develop a particular fabric characteristic. In all of these cases the chemical properties of the fabric, with the exception of added dyes, are those of the const i tuent fibre. The factors governing the flammability behaviour of fibres are complex, particularly when more than one fibre is present in the fabric. Blends of two fibres are common but some fabrics may contain four and five fibre types. All textile fibres consist of long chains of polymeric materials and the burning behaviour of the fibres is determined largely by the chemical properties of these materials. The behaviour of fabrics made from one fibre type to heat and flame is well documented. However, the flammability of fabrics made from two or more fibres generally cannot be predicted from the properties of the component fibres and only limited information on specific blends is available. This is because of the large number of conventional and flameretardant (F.R.) fibres available to the textile industry. At least 86 F.R. fibres alone, divided into 18 broad chemical categories, are available from fibre producers [ 1]. The situation is complicated further by the fact that during textile manufacture other polymeric materials, as oils, lubricants or polymers, can be applied to fibres to improve processing and fabric performance. When such materials are present on the fabric the burning behaviour of the fabric must be expected to change. The chemical nature of these additives is at least as diverse as those of the textile fibres and of the processes used to render them flame-retardant. However, despite the enormous effort directed to the development of F.R. fibres and finishes little work has been directed to the properties of multifibre fabrics and even less to the important area of compatibility of flame retardancy with additive textile finishes. In this paper the use of polymers in textile finishing operations is reviewed and the effects of dyeing, bleaching and polymer treatments on flammability behaviour are discussed. Some information on finishing blended fabrics is presented.

The Effect of Tetrakis(hydrogymethyl)phosphonium Chloride (THPC) on Selected Properties of Fibers

The effect of tetrakis(hydroxymethyl)phosphonium chloride (THPC) on the physical and chemical properties of wool. cotton, rayon, nylon, and polyester was examined. THPC had the greatest effect on wool, reducing its flammability and decomposition temperature and increasing the extensibility and dyeability of the fiber. The effect of THPC on cotton and rayon differed, primarily due to the greater extent of reaction of THPC with rayon than with cotton. Both cellulosics became slightly more flame retardant, their decomposition temperatures decreased, and both became more weak and brittle. In addition, THPC-treated rayon showed improved wet wrinkle recovery and dyeabitrty with d rect dyes. THPC reacted with nylon to give a more flame retardant fiber of lower decomposition temperature and greater dyeability, but the treated nylon also exhibited inferior tensile properties. Polyester did not react significantly with THPC and showed only slight changes in properties. THPC treatment had a marked effect on the fibers, and this effect should be considered when preparing finishes containing this reagent.

Differential Thermal Analysis (DTA) and Thermogravimetric Analysis (TGA) Studies of Flame-Retardant Rayon Fibers

The thermal behavior of flame-retardant fibers in which the flame-retardant chemical trapped inside the regenerated cellulose has now been studied, by differential thermal analysis (DTA) and thermogravimetric analysis (TGA). The thermograms obtained in a dynamic air atmosphere resemble those previously reported elsewhere for cellulosic materials treated with flame retardants in the conventional manner. In all cases, it has been found that the thermal degradation of the flame-retardant fibers begins at a lower temperature than for the control. A smaller quantity of flammable volatile matter is evolved and a much larger residue remains when the pyrolysis is complete. The total area of the exothermic peaks is, therefore, much smaller for the flame-retardant fibers than for the control. When the same flame-retardant fibers are heated in a nitrogen atmosphere, it can be easily seen that the onset of decomposition occurs quite suddenly at a definite temperature and clearly involves a reaction between the flame retardant and the cellulose. Examination of the flame-retardant chemicals themselves shows that these materials undergo a chemical change at approximately the same temperature, and it is this change that precipitates the interaction with the cellulose. Heating the flame-retardant rayon fibers in a conventional Fisher-Johns melting point apparatus shows that, although scorching occurs at lower temperatures than for untreated rayon, the difference is not large enough to have any effect on the processing or care of fabrics made from these fibers.

USDA cotton-flameproofing treatment

Thermal properties of fabrics made of Nomex 462 and Lenzing Viscose FR (Flame-retardant) fibres were analysed. After vertical burning, Limiting Oxygen Index (LOI) and Thermal Gravity (TG) tests it was discovered that the blended material compared favorable with the 100% Nomex goods in thermal behaviours. Among the seven fabric groups with various ratios of the two components, Sample No. 6 with the blended ratio of 80/20 (Nomex/Lenzing Viscose FR) demonstrated excellent thermal properties, in which case the LOI value was the highest and damaged length in vertical burning test the shortest. By blending Nomex and Viscose FR filaments to produce flameproof fabric may be an economical choice because of the lower price of the later component.