- 1 Introduction
- 1.1 Flame Retardants For Cellulosics
- 1.2 Historical Background Of Flame Retardant
- 1.3 Classes Of Flame Retardants
- 1.4 Basic About Burning About Any Material
- 1.5 Experiment
- 1.6 Testing Methods Of Flame Retardant Finished Fabric
- 1.7 Flame Retardant Finish Mechanism On Textile Materials
- 1.8 Methods Of Flame Retardant Finish On Cotton Fabric
- 1.9 Applications Of Flame Retardant Finished Fabric
- 1.10 Evaluation Of Flame Retardants
- 1.11 Conclusion
- 1.12 Related
Even though the use of synthetic fibres has grown during the last years, cotton is still one of the most important fibrous materials in the textile industry.
Due to the excellent textile properties such as strength, flexibility and air permeability of these naturally grown fibres a variety of different applications are possible.
Furthermore, it is to highlight that cotton is a renewable raw material. In order to expand the possible applications of a given textile additional desired properties can be introduced by textile finishing processes.
Regarding safety aspects, the flame retardant treatment is an important finishing process. This has been an active field of research for over sixty years.
This article discusses clearly the dominant species of flame retardant, the historical background of flame retardant, classes of flame retardant, experiment, mechanism of flame retardant finish and evaluation of flame retardant finish on 100% cotton fabric.
Flame retardants are the chemicals which are added to combustible materials to render them more resistant to ignition. Flame retardants are added to some products with the purpose of making it more difficult for a fire to develop.
Flame retardants are added to products of flammable materials such as textiles, foam materials and plastics i.e. carpets, mattresses etc.
The flammability of cotton products is one of the major problems posed to scientists and technologists at the present time. Resistance to burning is a useful property that can be imparted to cotton fibers and fabrics.
There is the potential for 2-3 million bales of cotton to be affected by flammability regulations and issues. The apparel portion of this is more than 1 million bales, with the remainder including categories such as home furnishing, bedding, tent cloth, carpets, aircraft and automobile interior fabrics and industrial fabrics.
Cotton and cellulosic textiles in general, while being among the most flammable of materials. Hazards from flammable fabrics were recognized for many centuries and repeated attempts have been made to cope with them.
Cotton is the most commonly used of textile fibers. It is not surprising that most efforts in the field of flame retardancy were made on modifying the flaming properties of cotton fibers.
There are currently several different types of chemical finishes that can be applied to cellulosic materials to impart flame retardant properties. Of these systems, only a few create finished fabrics that can be laundered and dry-cleaned without losing their flame retardant qualities.
These treatments are generally referred to as “durable flame retardant finishes” and, for the most part, can be summed up by referencing two types of commercial finishing chemistries: pre-condensate ammonia cure; and N-methylal functional phosphorus esters.
It is surprising that more than thirty years have been passed since these chemistries were first developed, and they still remain the dominant means for creating durable flame retardant cotton.
Flame Retardants For Cellulosics
Flame retardant finishes present on specific textiles, based on the durability of flame resistance, are defined as non-durable, semi-durable, and durable with respect to a given condition.
1. Non-Durable Flame Retardants For Cellulosics
Nondurable flame retardants for cellulosic are generally water-soluble inorganic salts that are easily removed by water, rain, or perspiration. They provide only temporary protection and therefore periodic reprocessing becomes necessary to maintain the flame retardant effect.
There are several groups of these materials. One group is based on boron derivatives, boric acid, and borax, sometimes in conjunction with ammonium salts of sulfuric and phosphoric acid, urea, and ammonium bromide.
2. Semi-Durable Flame Retardants For Cellulosic
Cotton treated with semi-durable flame retardants should withstand a limited number of washes. These materials are ammonium polyphosphate, and usually insoluble salts of amphoteric cations and anions-stannates, tungstates, aluminates, borates, and phosphates of Zn, Sn, Al and easily reducible metallic oxides-Sn, Fe, Pb, Ti, Cr, Zr, Ce, Bi, W, and A .
Direct application of insoluble salts has its limitations and best results occur by internal precipitation following application of a reagent solution. For instance, metastannic acid, H2SnO3 may be formed following hydrolysis of an applied stannic salt, such as SnCl4, or by acidification of a soluble stannate.
In a similar manner, chromium hydroxide and tungstic acid may be precipitated by similar respective methods.
3.Durable Flame Retardants For Cellulose By Sulfation-Phosphorylation
Sulfation of cellulose with ammonium sulfamate (AS) in the presence of urea or urea-based cross-linking agents imparts to cellulose an excellent flame resistance that is durable to over 50 alkalines soft- and hard-water launderings. A weight gain of ~10% corresponding to 3% bound sulfur was found necessary to obtain this effect.
The sulfated fabrics exhibited a high degree of afterglow. It was shown that this severe after-glowing could be overcome by the addition of phosphorus either by after-treatment with DAP, which is not durable or by a combined and simultaneous sulfation and phosphorylation treatment with ammonium sulfamate and phosphorus triamide.
Historical Background Of Flame Retardant
Initially, flame retardant materials were first created around 400 B.C, but the need for them didn’t increase drastically until the 17th century. In 1632, the idea of reducing the risk of fire in theatres came about in Paris.
In the 18th century, alum and ammonium were used to make fabrics flame resistant. The first serious experiment took place in 1820. A chemist named Gay-Lussac determined that two types of salt helped to make fabric flame retardant. The first was low melting and formed a glassy layer on fabrics, and the second salt broke down into a nonflammable vapor when it was heated up.
The discovery of Tetra phosphonium chloride in 1953 advanced the process of making fabrics resistant to flames. THPC could be applied to cotton, paper, plastic, paint, furniture and other building materials. The flammable fabrics Act of 1953 changed how clothes were manufactured and sold.
Classes Of Flame Retardants
- Additive Type
a). Mineral compound, aluminum hydroxide, magnesium hydroxide
- Reactive Type
a). Organic halogen compounds, organochlorines, bromines
b). Organo phosphorus compounds as tri phenyl phosphate etc.
c). Halophosphorus compounds having halogen and phosphorus.
Basic About Burning About Any Material
The limiting oxygen index (LOI) is the minimum concentration of oxygen, expressed as a percentage, that will support combustion of a polymer.It is measured by passing a mixture of oxygen and nitrogen over a burning specimen, and reducing the oxygen level until a critical level is reached.
LOI values for different plastics are determined by standardized tests, such as the ISO 4589 and ASTM D 2863.
It is an exothermic process that requires three components,
- Suiting climate.
Pyrolysis Temperature, TP
At this temperature, the fibre undergoes irreversible chemical changes.
At this point, the flammable gasses combine with oxygen in the process called combustion.
Aim: Application of flame retardant finish on 100% cotton.
The fabric is padded through the solution containing:
- THPC -15.8%
- Methylol melamine – 9.5%
- Tri ethanol amine – 3%
- Urea – 9.9%
Dried and cured at 140* C for 5 minutes and washed. This process is known as “Proban” finishing.
Process Sequence :
Testing Methods Of Flame Retardant Finished Fabric
1. The Vertical Timing Test
In this test, the rate of flame spread is determined over fabric suspended vertically.
2. The 45° Test
In this test the time t, the flame to travel 5 inches over fabric slopping at an angle of 45° is measured in seconds.The flame resistance rating, M, is then given by 2.5× t.
3. The Hoop Test
In this test, the ratio of flame spread is determined over the fabric mounted on a semicircular frame.
Flame Retardant Finish Mechanism On Textile Materials
1. Condensed phase-mechanism
The substrate, under the influence of externally applied heat, undergoes thermal decomposition (pyrolysis) with the generation of combustible fuel.
Only a part of this fuel is combusted in the flame by combining with atmospheric oxygen. The other part remains and can be combusted with the use of a catalyst by an excess of oxygen.The flame provides a part of its heat for the continued pyrolysis of the substrate, perpetuating the cycle. Another part of the heat is dissipated and lost to the environment.
Cellulose decomposes by a noncatalyzed route to tarry depolymerization products, notably levoglucosan, which then decomposes to volatile combustible fragments such as alcohols, aldehydes, ketones, and hydrocarbons.
A flame retardant that acts via a condensed-phase mechanism catalyzes the decomposition of cellulose more effectively, through the formation of water vapor and char, and reduces the formation of volatile flammable gas.
2. Vapour-Phase Mechanism
In the condensed-phase mechanism, the effect of the flame retardant is concentrated on decreasing the amount of fuel produced in the pyrolysis. In the vapor-phase mechanism, the pyrolytic processes remain essentially the same with or without FR; however, the mode of combustion in the flame is changed.
The amount of fuel consumed in the flame and consequently the amount of heat generated are decreased with an increase in the amount of flame retardant. The amount of heat returned to the polymer surface is therefore also diminished and the pyrolysis is slowed down or halted as the temperature of the surface decreases.
Since the flame-retarding effect is being exerted in the gas phase only, it follows that the flame retardant moiety has to reach the gas phase, i.e., it has to be volatile and reach the flame. Alternatively, it has to decompose and furnish the active flame retardant fraction of its molecule to the vapor phase.
The remaining char after the combustion will retain a much smaller percentage of the FR chemicals as compared with the condensed-phase flame retardant. Chemical analysis of the char is, therefore, one of the ways in which the mode of activity of the FR chemical can be determined.
Furthermore, the flammability in the vapor-phase mechanism should be basically independent of the structure of the polymeric substrate. It should also not introduce any changes in the pyrolytic process, which ideally should proceed as if there would have been no FR chemical incorporated in it.
The composition of the volatiles in the flame should therefore also not be influenced by the presence of the vapor-phase-active FR agent. The vapor-phase activity of the flame retardant is attributed to its interference in the combustion reactions in the flame.
Methods Of Flame Retardant Finish On Cotton Fabric
(i) Padding Baking Process
The process flow of the method is Padding preliminary drying baking after treatment. Its padding liquor is a flame retardant solution, commonly be formed of flame retardant, crosslinking agent, catalyze, wetting agent and softener, either formulate become water solution or lattices proceed tidy.
(ii) Steep Parch Dry Farad
The process flow is Steep dryness after treatment. It holds fabric lay in flame retardant liquor suffer steep hour to it, take out and drying, at times flame retardant finish approve to dyeing with bath proceed.
(iii) Extrusion Coating Farad
It is number flame retardant interfusion resin within proceed process. warranty the different of mechanical equipment into knife coating farad, molding extrusion coating farad and recycle extrusion coating farad.
(iv) Spray Method
Put out of service conventional equipment art fictitious thick curtain, large-scale rug and more merchandise, the flame retardant finish of the approve last of all in a single operation did hand spraying farad. Toward bulkiness surface has got the figure, tufting, pile cottony fabric, used padding farad dispose of surface fuzz figure came in for traumata to, commonly adopt series spray method.
(v) Organic Solvent Farad
The used organic matter should flame retardant dissolve, then proceed flame retardant finish, it is able to gotten put hour shorten to rights. In course, both it has to be noted that solvent virulence and combustibility.
Applications Of Flame Retardant Finished Fabric
Evaluation Of Flame Retardants
Evaluation of flame retarding performance and stiffness of the fabric.The vertical flammability of the fabric was measured according to ASTM standard method D6413.
The limiting oxygen index(LOI) of the fabric was measured according to ASTM standard method D2863.The fabric stiffness was measured according to ASTM standard method D6828 using a “Handle-o-meter” tester manufactured by Thwing-Albert, Philadelphia.
- This review demonstrated that the application of THPC, methylal melamine and tri ethanol amine on a cotton substrate was\ an effective process for achieving the flame retardant performance of the fabric by click chemistry.
- The flame retardant performance of the treated fabric was assessed by the vertical flame test, the visual timing test and the hoop test was found to be significantly better.
- The LOI of the finished fabric was increased compared to the original cotton, LOI of the treated cotton fabric after washing was improved.
- Moreover, the treated fabric possessed excellent mechanical properties, and the whiteness of the untreated and the treated fabrics were similar.
- Alcan Chemicals. (2000). Flame retardants: some new developments[J]. Plastics Additives Compounding, 2000.
- Cui J, Jiang H L, Wu M Y, et al. (2003). The actuality and trend of development of the flame retardant[J]. Shandong light industry institute transaction, 2003.
- Liu L W, Guo F, Chen J F. (2004). The nanometer alumina cream flame retardant surface modification and the application of it used in polypropylene[J]. China plastic, 2004,18(2): 74-77.
- Drake, G. L., Jr., Chance. L. H. and Reeves, W.A., Fire Retardant Chem., 1, 110 (Feb.. 1974).
- A study of fire Retardancy of cotton sheeting, Am, Dyest, Rep., 57(10) 373 (may 6, 1968).
- Horrocks AR, Flame retardant finishing of textiles, Review of Progress in Coloration and Related Topics 1986, 6 (1) 62- 101.
- Kishore K, Mohandas K, Action of phosphorus compounds on fire- retardancy of cellulosic materials: a review, Fire and Materials 1982, 6 (2), 54- 58.
- Faheem Uddin, Concerns of brominated flame retardant, Industrial Fabric Bulletin 2003, 3, 55- 56.
- Jennifer Tata, Jenny Alorgi, Alberto Frache, Optimization of the procedure to burn textile fabrics by cone calorimeter: Part II. Results on nanoparticle- finished cotton, Fire and Materials, Volume 36, (2012) 527- 536.
- Roberts DL, Hall ME, Horrocks AR, Environmental aspects of flame retardant textiles- an overview, Review of Progress in Coloration and Related Topics 1992, 22 (1), 48- 57.
- Yang D X. (1989). Flame retardant finish. Printing and dyeing, 1989, 15(6 ): 47-54. Sun H Z, Longhai Cong. (2004). The application and develop of textile flame retardant finish technology[J]. Qiqiha’er university transaction. 2004, (3): 32-35.