EVALUATION OF FLAMERETARDANT FINISHESFARBRIC AND GARMENT FINISHING4/26/2012BFT SEM IVABHISHEK KUMAR (M/BFT/10/03)ALISHA KAPOOR (M/BFT/10/04)ANKIT GHOSH (M/FT/10/05)
INTRODUCTION TO FLAME RETARDANCEFlame retardants are materials that have the quality of inhibiting or resisting thespread of fire. Textile is highly ignitable and contribute to rapid fire spread.However, the ignitable property of a textile can be considerably reduced by anyone of the three methods- by using inorganic materials such as Asbestos, Glassetc; by chemically treating the textile with Flame Retardant chemicals; and bymodifying the polymer.Categories of Flame RetardantsThere are many categories in which flame retardants can be divided. The majorcategories among them include: • Tetrakis (hydroxymethyl) phosphonium salts that are made by passing phosphine gas through a solution of formaldehyde and a mineral acid like hydrochloric acid. This category is mostly used as flame retardants for textiles. • Minerals like asbestos, compounds such as aluminum hydroxide, magnesium hydroxide, antimony trioxide different hydrates, red phosphorus, and boron compounds, mostly borates. Etc. • Synthetic materials, usually halocarbons which include organochlorines such as polychlorinated biphenyls (PCBs), chlorendic acid derivates and chlorinated paraffins; organobromines such as polybrominated diphenyl ether (PBDEs), organophosphates in the form of halogenated phosphorus compounds and others.Types of flame retardants are: • Chlorinated flame retardants • Phosphorous-containing flame retardants (Phosphate ester such as Tri phenyl phosphate) • Nitrogen-containing flame retardants (i.e. Melamines) • Inorganic flame retardants.
Other method of classifying Flame Retardants is to divide them as Inorganic,Organo Phosphorous, Halogenated organic and Nitrogen based compounds.Halogenated organic flame retardants are further classified as having eitherChlorine or Bromine which is popularly known as Brominated FlameRetardants (BFR)How do Flame Retardants WorkFlame retardant chemicals that are applied to fabrics are intended to inhibit orsuppress the combustion process. These fire retardants interfere withcombustion at different stages of the process like during heating,decomposition, ignition or spreading of flame. For understanding how flameretardants resist fire, first it should be known how a textile is heated up, catchesfire and contributes in spreading it.As with any matter, a textile fabric exposed to a heat source experiences rise intemperature. If the temperature of the fire source is high enough and the net rateof heat transfer to the fabric is great, pyrolytic decomposition of the fibersubstrate occurs. The products of this decomposition include combustible gases,non combustible gases and carbonaceous char. The combustible gases mix withthe surrounding air and its oxygen. The mixture ignites, yielding a flame. Ithappens when the composition of textile and the temperature, both arefavourable. Part of the heat generated within the flame is transferred to thefabric to sustain the burning process and part is lost to the surroundings.Now, if the textile is flame resistant then the flame retardant can act physicallyand/or chemically by interfering at particular stages of burning. There aredifferent mechanisms of flame retardants.Mechanisms of Flame RetardantsFlame retardants can act physically or chemically and sometimes both byphysically and chemically interfering at particular stages of burning. Thedifferent mechanisms are:Endothermic Degradation : Certain compounds break down endothermicallywhen they are subjected to high temperatures. Magnesium and aluminiumhydroxides are such examples. Various hydrates also act similarly. The reaction
takes off heat from the surroundings, thus cooling the material.Dilution of Fuel: Substances, which evolve inert gases on decomposition,dilute the fuel in the solid and gaseous phases. Inert fillers, eg. talc or calciumcarbonate, act as diluents, lowering the combustible portion of the material, thuslowering the amount of heat per volume of material that it can produce whileburning. Thus the concentrations of combustible gases fall under the ignitionlimit.Thermal Shielding : A thermal insulation barrier is created between theburning and the yet-to-burn parts. Intumescent additives are sometimes appliedthat turn the polymer into a carbonized foam, resultantly separating the flamefrom the material and slowing down the heat transfer to the unburned fuel.Dilution of Gas Phase : Inert gases, mostly carbon dioxide and water, act asdiluent of the combustible gases, lowering their partial pressures and the partialpressure of oxygen, thus slowing the reaction rate. These gases are produced bythermal degradation of some materials.Gas Phase Radical Quenching : Chlorinated and brominated materialsundergo thermal degradation and release hydrogen chloride and hydrogenbromide. 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 radicalhas much lower energy than H. or OH. and thus has much lower potential topropagate the radical oxidation reactions of combustion. Antimony compoundstend to act in synergy with halogenated flame retardants. The HCl and HBrreleased during burning are highly corrosive, which has reliability implicationsfor objects subjected to the released smoke.
Flammability Standards and TestingStandards and testing are vital in ensuring that the flammability performance ofa fabric is satisfactory for a specific end-use. DESCRIPTION OF VARIOUS TESTING STANDARDSEN 532 : Limited Flame SpreadEN 532 measures the flammability of the material : the surface ignition lasts 10seconds.Requirements :Afterflame time < 2 sec.Afterglow time < 2 sec.No flaming to top or either side edge of specimen
No hole formationNo flaming or molten debrisEN 367 : Heat transfer (convectice heat) – Codeletter BEN 367 measures the rate at which materials transmit convective heat from oneside of the material to the other, by evaluating the time for temperature to rise tolevel of pain (HTI12) and 2nd degree burns (HTI24). The incident heat flux is80 kW/m² .Levels Requirements :B1 3 < HTI < 6 sec.B2 7 < HTI < 12 sec.B3 13 < HTI < 20 sec.B4 21 < HTI < 30 sec.B5 HTI > 31 sec.EN 366 Method B : Heat transfer (radiant) – Code letter CEN 366B measures the rate at which materials transmit radiant heat from oneside of the material to the other, by evaluating the time for temperature to rise tolevel of pain (t1) and 2nd degree burns (t2). The incident heat flux is 20kW/m² .Levels Requirements :C1 8 < t2 < 30 sec.C2 31 < t2 < 90 sec.
C3 91 < t2 < 150 sec.C4 t2 > 151 sec.All clothing assemblies claimed to offer protection against convective heat shallmeet at least level C1. topEN 373 : Molten metal splashes - Codeletter DEN 373 is the assessment of resistance of materials to molten metal splashes :molten aluminium and molten iron. The pouring temperature is 780°C± 20, thepouring height (mm) is 225 ± 5, and the specimen angle (deg.) is 60 ± 1.Levels RequirementsD1 100 < g < 200D2 201 < g < 350D3 g > 351All clothing assemblies claimed to offer protection against molten aluminiumshall meet at least level D1.EN 340 : Dimensional changeEN 340 gives an indication of the dimensional change due to cleaning.Requirement :Dimensional change < 3%, in length and width.
Marking :All protective clothing which is claimed to comply with EN 531 shall bemarked with the following information : Name, trademark or other identification means. Type designation, trade name or code for clear identification. Size designation (ref EN 340) Pictogram (below) incorporating the number of this standard and theperformance levels for property A and at least one other property, B to E.EN 1149 : Electrostatic propertiesEN 1149:1 specifies electrostatic requirements and test methods for electrostaticdissipative protective clothing to avoid incendiary discharges. The material isplaced on an insulating base plate and an electrode assembly is rested on thematerial. A DC potential is applied to the electrode assembly and the resistancein Ohms (W) of the fabric is measured.Requirements :The clothing shall be designed to allow a charge dissipation throughout thegarment.Surface resistivity < 5 x 1010 WEN 1149:2 is the test method for measurement of the electrical resistancethrough a material (vertical resistance). Electrodes are placed on oppositesurfaces of the material tested. A d.c. potential is applied to the electrodes andthe vertical resistance of the test material is determined.EN 1149:3 specifies two methods for measuring the dissipation of electrostaticcharge from the surface of materials for garments. The test methods areapplicable to all materials, including homogeneous materials andinhomogeneous materials with surface conducting fibres and core conducting
fibres.In one test method, the charge is achieved by rubbing the test material directlyagainst cylindrical rods. In the other test method charging of the material iscarried out by an induction effect, without direct contact.The maximum field strength and the rate of decay are recorded. An equivalentsurface resistivity can be calculated and it should be < 5 x 1010 W.BS 5852 testFire test for furniture - ignitability of upholstered composites. Tests ofresistance to ignition by sources 0 (cigarette) and 1 (match) have now beenreplaced by the corresponding parts of BS EN 1021.This test is sometimes known as the crib test. Crib test 5 is a commonly usedstandard indicating a higher fire resistance than the EN2021 test.A specially constructed test rig is designed to form a simulated chair asdescribed in EN 1021. The foam used is not specified. Eight Ignition Sourcesare defined: cigarette (0), match (1), butane flames (source 2 and 3), woodencribs (4, 5, 6 and 7). Moving up the scale the heat intensity increases.Results of these tests are used to ascertain a products suitability for use indifferent environments as described in BS 7176.The Ignition Source 5 test is more rigorous than the cigarette and match testsdue to the increased heat intensity. A flammable liquid is added to the smallpiece of lint at the bottom of the crib which is then placed on the test rig andignited within 2 minutes.For a pass to be recorded in the Ignition Source 5 test, all flaming should ceasewithin 10 minutes. Flames cannot penetrate the full thickness of the compositeand there must be no progressive smouldering more than 100mm either side ofthe ignitionNFPA 701, 1989 small scale test (Used for drapes)Test Flame Pass Criteria1989 Small Scale 1.5 inches No more than 6.5” average char length for 12 seconds No more than 7.5” individual char length No more than 2 seconds drip burn
I S O 6 9 4 0: 2 0 0 4ISO 6940:2004 specifies a method for the measurement of ease ofignition of vertically oriented textile fabrics and industrial products inthe form of single or multi-component fabrics (coated, quilted,multilayered, sandwich constructions, and similar combinations), whensubjected to a small, defined flame. This method assesses theproperties of textile fabrics in response to flame contact undercontrolled conditions.