IGNITION RESISTANT LATEX COMPOUNDS IN CARPET BACKING APPLICATIONS

Presented by:

Keith Woodason Senior Development Specialist The Dow Chemical Company

2864 North Dug Gap Road SW, Dalton GA 30720 Phone: 706-277-8145 ● Fax: 706-277-8100 ● Email: kjwoodason@dow.com

Keith Woodason is a Sr. Development Specialist working in the Emulsion Polymers business of The Dow Chemical Company. He has held a variety of Manufacturing & Engineering positions in both the SARAN™ Barrier Resins and Superabsorbent Products businesses within Dow. He is a certified Six Sigma Black Belt currently working in Technical Service & Development serving customers in the carpet industry. Keith graduated with a B.Sc. degree in Chemical Engineering from Rose-Hulman Institute of Technology in 1989.

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Ignition Resistant Latex Compounds In Carpet Backing Applications

Keith Woodason The Dow Chemical Company

Abstract Federal standards govern the flammability of carpet produced in the United States in addition to many local building and fire codes. Carpet manufacturers often find it necessary to improve the ignition resistance of their products with the addition of certain types of flame retardant additives and/or synergists to the carpet backing compound. An overview of combustion theory and resistance mechanisms is provided along with a review of the current state of flame retardant technology used in the carpet industry. The development of a high solids, inherently ignition resistant terpolymer latex for both commercial and residential carpet backing applications is also highlighted. Introduction Flammability characteristics of building materials and furnishings significantly impact the speed at which a fire spreads. As the rate of fire spread is reduced, the likelihood of saving lives and minimizing property damage is increased.1 The flammability of carpet produced for both the residential and commercial carpet market segments is a critical performance factor that may significantly influence human health and safety. A majority of the raw materials used in the manufacture of today’s carpeting are synthetic polymers. Many of these materials require the use of flame retardants to meet certain flammability requirements. Flame retardants function by removing one of the three components of the fire triangle; heat, fuel, or oxygen. Testing of various polymers in household components has shown that heat generation in fires is typically lower in fire retarded products than their non-fire retarded counterparts. This observation is most likely due to a reduction in the total mass of material consumed in the fire, a lower temperature of combustion, and significantly lower peak heat release rates. The use of flame retardants in carpet backing systems typically adds to the manufacturing cost of the carpet and may reduce the resultant carpet physical properties as well. It is important to optimize the flammability performance, the cost of manufacture, and other criteria such as appearance retention, tuftbind, and resistance to delamination. Combustion Theory Combustion of polymers is a two-phase process which involves the pyrolysis of a solids followed by the flame propagation of a vapor. The polymer solid provides the fuel and in turn, the combustion of the flammable pyrolysis gases supplies heat back to the polymer. The third necessary ingredient for combustion is oxygen supplied by the surrounding air. At least six steps have been identified in this process. 2 A simplified diagram of this process is shown in Figure 1.

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combustiblegases heat

Polymer

free radical enabled reactions ●OHsolid polymer ●HCO H O22O2heat smaller

molecules

Figure 1. Combustion Process

The heating of the polymer solid is purely a physical process. Pyrolysis and combustion involve complex chemical reactions 3 Solid polymers do not burn directly, they must first be broken down into smaller molecules that will react with oxygen in the air. If the polymer does not pyrolyze, it will often smolder and self-extinguish. After the solid polymer temperature reaches a critical level, thermolytic cleavage of the chemical bonds occurs subsequently releasing flammable and volatile pyrolysis gases. These gases mix and exothermically react with oxygen in the ambient air to form carbon dioxide, water, and incomplete reaction products. This process, known as combustion, involves intensive free radical chain reactions and subsequent release of large amounts of energy in the form of heat.4 The free radical propagation of the process is outlined in a simplified form in Figure 2.

+

+CO ●OH CO ●H2

●H + +O2 ●OH O

Figure 2. Free Radical Propagation of Vapor Phase Reaction The hydrocarbon fuel from the polymer is the source of the hydrogen and carbon while oxygen is available from the ambient air. Carbon monoxide is the product of incomplete combustion. Complete combustion yields carbon dioxide and water. It is unclear whether the ●OH or ●H reaction is the rate limiting step in the propagation process.5

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Fire Retardant/ Ignition Resistant Technology in the Carpet Industry In order for a flame retardant to function, it must interfere with one or more of the previously identified steps of the combustion process. Many flame retardants are considered to be multifunctional in that the specific compound demonstrates more than one interference mechanism. Building on the six steps of combustion detailed earlier, proposed interference mechanisms associated with each step are listed in Table 1.

Table 1. Flame Retardant Mechanisms

Combustion Step Flame Retardant Mechanism 1. Heating of solid material

Keep material cool6

2. Pyrolysis

Use materials that do not degrade, or have high thermal stability, or degrade to noncombustible gases, liquids, and solids7

3. Evaporation of the volatile decomposition products

Make nonvolatile decomposition products or render the volatile products nonvolatile in-situ8

4. Ignition of material

Maintain temperature below minimum ignition temperature of the material

5. Oxidation of the vapor

Eliminate oxygen sources by reaction or blanketing9

6. Propagation

Eliminate free radicals from the vapor phase10

The type of face fiber has a significant impact on the flammability of the finished carpet. Polypropylene is less ignition resistant than nylon. Wool is quite ignition resistant and is specified for many stringent floor covering applications such as aircraft and ships. Blended fiber systems can sometimes improve the ignition resistance of a single component yarn. Scouring, or washing of the griege goods prior to finishing, removes the spinning lubricants and blooms the yarn. Typically, scouring will result in improved FR/IR properties and face appearance of the carpet.11 Carpet construction also plays a major role in determining the final product flammability. The ratio of flame retarded coating weight to available fuel weight is a critical factor in system performance.12 The total fuel weight is comprised of yarn, primary backing, secondary backing, and the non-ignition resistant polymer portion of the latex coating weight. Typically, the face fiber comprises the majority of the total polymer content of carpet. The face fiber weight can range from 10 to over 100 oz/yd2. Latex based backing systems usually consist of a precoat compound applied to the back of the carpet and an adhesive compound applied to the secondary backing. Even though the typical total compound coating weight ranges from 20 to 45 oz/yd, the polymer component is usually

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only 3 to 15 oz/yd. Ideally, it would be better to address flammability issues with the face fiber, however, due to cost and marketing constraints, the backing system is required to overcome any deficiencies. When some polymers undergo thermal decomposition, reactive side groups are detached from the main polymer backbone and a carbonized polymer residue is left behind called char. The formation of char strongly influences both heat and mass transfer. The surface structure of intumescent systems, which form foamed char during combustion, changes drastically over time.13 This foamed char can also act as an extremely efficient insulating layer. Many polymers such as polystyrene, polypropylene, and acrylonitrile-styrene-butadiene don’t form char under fire conditions, but rather depolymerize to monomers and oligomers. Other polymers, such as ethylene vinyl acetate (EVA) and polylactic acid (PLA) are good char formers. However, there is a difficulty with charring as an interference mechanism in carpet backings. The primary fuel source is the fiber and primary backing which are next to the flame above the latex backing system and charring of the backing system will not limit heat or mass transfer to these sources. More effective mechanisms are likely to be cooling, inhibition of vapor phase propagation, and dilution or elimination of oxygen. Much of the latex used in carpet backing systems is carboxylated styrene-butadiene polymer, although EVA isused primarily as a precoat compound for PVC backed tile applications based on resistance to plasticizer migration problems common to styrenic polymers. Various acrylic latex products are also used in carpet backings albeit to a much lesser extent. Halogenated polymers used in latex based carpet backing compounds have included vinylidene chloride styrene butadiene (VSB), vinylidene chloride butadiene (VB), polyvinyl chloride, and ethylene vinyl chloride. Polyurethanes are also used extensively in the carpet industry in both two-component reactive systems as well as aqueous polyurethane dispersions. Polyurethane demonstrates good ignition resistance, however, attached cushion typically acts as an insulator and can impact flammability performance of the carpet as a whole. Focus in the carpet industry on recycling of backing systems has led to the development of polyolefin based backing systems. One may theorize that it would be more difficult to pass flammability standards with these types of backing systems. In addition to polymer type, filler type and load levels also impact carpet flammability. With the current trend being to increase recycle content in carpet, especially in the commercial carpet market segment, reclaimed coal fly ash (CFA) and ground glass are becoming more prevalent in replacing a portion of the ground calcium carbonate fillers typically used in latex based carpet backing compounds. These should be similar to calcium carbonate with respect to ignition resistance. Each polymer system has its own decomposition mechanisms under fire conditions. Some of the chemical pathways are known, while some are less defined. Greater understanding of the thermal degradation pathway may lead to the development of more effective resistance mechanisms to prevent polymer combustion.14 In theory, all four halogens (bromine, chlorine, fluorine, and iodine) demonstrate ignition resistant activity. Fluorine is not typically used, because hydrogen fluoride is not stable

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enough to reach the flame front. Iodine is active, but hydrogen iodide is too stable to be released in most test conditions. On a molar basis, bromine is over twice as effective as chlorine due to its higher atomic weight and higher bond energy for most hydrogen-bromine compounds compared to the hydrogen-chlorine analogs.15 However, due to atomic weight differences, roughly twice as much bromine as chlorine is needed on a weight basis to be equivalent on a molar basis. The four proposed flame retardant mechanisms by which halogens affect the combustion process are listed below:16

1. Free radical or Chemical Mechanism – the halogen influences free radical propagation in the vapor phase. A chemical mechanism is proposed in Figure 3 which builds on the propagation mechanism listed in Figure 2 affecting step 6 of the combustion process listed in Table 1. It is important to note that the ●R free radical is unable to sustain the heat release rate needed to maintain flame spread.

2. Coating Mechanism – The noncombustible HX gas, where X is the halogen, covers the combustible products of the condensed phase preventing oxidation, or by crosslinking causes nonvolatile decomposition products to form affecting steps 2 and 3 of Table 1.

3. Blanketing – The HX gas dilutes or eliminates the oxygen from the vapor reaction ending further flame advance affecting step 5 of Table 1.

4. Cooling – All halogen reactions taking place are endothermic and remove energy from the system. Also, the specific heats of combustion of the polymer may be affected by monomer choice. For example, the specific heat of polyvinylidene chloride is -3870 BTU/lb, whereas the specific heat of polystyrene is -17878 BTU/lb. Therefore, replacing styrene with vinylidene chloride will contribute roughly 4.6 times less energy during combustion affecting steps 1 and 4 of Table 1.

Figure 3. Halogen Inhibition of Vapor Phase Propagation

Propagation: CO + ●OH CO + ●H 2

Inhibition: HX + ●OH H2O + ●X

Propagation: ●H + O2 ●OH + O Inhibition: ●H + HX H2 + ●X ●X + RH HX + ●R

Brominated Flame Retardants (BFR) are used in polymers to minimize the loss of lives and property, and as such have a direct and obvious benefit. However, concerns have been raised over their persistence, bioaccumulation, and potential for both animal and

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human toxicity.17 Polybrominated diphenyl ethers (PDBE) are of primary concern. Voluntary bans of PBDEs are already in effect in much of Europe and Japan. The European Union has legislatively banned the use of pentabrominated and octabrominated diphenyl ethers in electronic and electrical equipment beginning in 2006. The State of California has also banned these compounds beginning in 2008. The primary toxic effect of brominated fire retardants (BFR) has been proposed to be the disruption of thyroid homeostasis.18 However, the existing toxicology database is inadequate to completely understand the risk of the production and use of BFRs.19 Antimony is used a synergist with halogens to enhance FR performance, but offers little improvement on its own. General product literature suggests a molar ratio of 3:1 (halogen:antimony) for optimum improvement of polymer ignition resistance.20 Usual forms of antimony used in the industry are antimony trioxide and antimony pentoxide. The proposed chemical synergy mechanism with chlorine suggests the antimony trioxide reacts with HCl gas to form SbOCl and water. Further reactions generate noncombustible SbCl3 gas. The SbCl3 gas interferes with the vapor phase propagation by generating HCl gas. Higher levels of antimony trioxide in carpet backing formulations can increase smoke generation in fire conditions. Typical strategies to reduce smoke generation in this case include increasing the amount of alumina trihydrate (ATH), increasing magnesium hydroxide, reducing calcium carbonate, reducing antimony trioxide levels, and adding zinc borate.21 Many current methods of flame retarding polymers involve an additive approach. This can have drawbacks chief among which is when the additive leaves the polymer matrix after compounding causing a decrease in flame retardant properties over time.22 General environmental concerns over halogens have caused much greater emphasis on the development of non-halogenated fire retardants such as nitrogen containing compounds, phosphorus based compounds, metal oxides and hydroxides, clays and organoclays as well as others.23 Potential release to the environment issues may be overcome by incorporating the FR species into the backbone of the polymer. Most non-halogenated formulations require large amounts of metal hydroxides to achieve the desired FR/IR performance.24 In the carpet industry, the preferred flame retardant is ground alumina trihydrate (ATH) which is used to replace a portion or all of the calcium carbonate filler in the backing system. ATH exhibits three combustion process interference mechanisms by decomposing at roughly 200ºC to aluminum oxide, which forms a nonflammable protective layer on the material surface, and water. Evaporation of the water is endothermic which absorbs heat and the water vapor dilutes the flammable gases. ATH is a very efficient flame retardant in the carpet industry. Alumina trihydrate is the largest volume flame retardant in the United States. In 2003, total carpet backing applications for mineral based flame retardants was estimated at $18.3 million.25 ATH pricing has driven some manufacturers to look for alternatives to ATH. Magnesium hydroxide is used to a lesser extent for the same purpose, but is less effective at the similar loadings. Ground bauxite has also been evaluated but backing

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compound formulations must be adjusted to overcome rheological stability issues which may cause additional cost and/or productivity concerns. The environmental and health concerns (real or perceived) that have impacted the use of brominated flame retardants have caused many to search for alternatives. Phosphorus compounds have become one of the candidates. Phosphorus compounds react to produce a polymeric form of phosphoric acid. The acid helps the polymer to char interfering with the further heating and pyrolysis of the polymer. Although effective, it is possible that organophosphorus compounds may cause similar health or environmental concerns to surface in regards to flame retardant polymers just as they did 10-15 years ago with halogenated compounds.26 Another issue with the use of some organophosphates to promote charring in latex based backing systems is the development of a sweet odor that is imparted to the carpet.27 Any odor associated with carpet, whether pleasant or unpleasant, is generally viewed as a negative product attribute. Nitrogen containing compounds, such as melamine and its derivatives, are used in flame retardant applications but have not been used extensively in the carpet industry for this purpose. It is expected that these compounds crosslink the material providing a barrier to heating and pyrolysis. Additionally, nitrogen is released upon decomposition which dilutes the hydrocarbon fuel from the polymer. These compounds are also thought to display synergy with phosphorus based flame retardants. Boron is one of the few elements in the periodic table that demonstrates some degree of flame retardancy.28 Zinc borate has been used as a smoke suppressant in carpet backing formulations and demonstrates some synergy with antimony compounds. In both general literature as well as patent literature, polymer systems which include a nanocomposite plus flame retardant generates material which has similar or better FR performance, improved mechanical properties, and a lower cost.29 Measurements of Flammability The primary flammability tests used in the carpet industry in the United States include the Department of Commerce FF 1-70 Pill Test, ASTM E-648 radiant panel test, and the ASTM E-662 NBS Smoke Density test. 30 Three additional Federal standards, 14CFR25.853 and 14CFR25.855 for aircraft, 46CFR116.423 for shipping, and 49CFR571.302 for vehicles reference floor covering flammability performance criteria based on vertical Bunsen burner tests similar to NFPA 701 or UL-94. The International Maritime Organization (IMO) also specifies a flammability test for deck coverings in ships in Resolutions A.653(16) and A.687.17. This test is similar to the radiant panel test only the specimen is mounted in a vertical orientation. Another test, ASTM D-2863 Oxygen Index, is useful in the evaluation of the flammability of materials used in carpets. The Consumer Product Safety Commission requires that all carpet and large rugs greater than 24 ft2 to pass a small-scale ignition test, known as the “pill test.”31 The primary

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purpose of this test is to determine the resistance of a carpet or rug to spreading the flame from an ignition source such as a lighted cigarette or glowing ember. A methenamine timed burn tablet is ignited in the center of a 9” by 9” sample of carpet within a draft protected environment. The sample is held flat with a 9 inch square metal plate with an eight inch diameter hole in the center. For a carpet to pass, the flame must not spread to within one inch of the flattening plate on seven of eight total specimens.32 Products that have been treated with flame retardants that enable the carpet or rug to pass the test must be labeled with the letter “T” and tested after a series of washings and dryings.33 An exemption from washing is in effect for carpets rugs with alumina trihydrate in the backing. The carpet manufacturer maintains the burden of compliance to this standard. Another fire scenario associated with floor coverings is a fully developed fire that radiates heat down onto the face in conjunction with an advancing flame front.34 The radiant panel test measures the critical radiant flux (CRF) at flame-out of horizontally mounted carpet exposed to a flaming ignition source in a graded radiant heat energy environment.35 An average CRF value of three specimens per sample is reported. Class I performance is defined as having CRF values greater than or equal to 0.45 W/cm2. Typical applications that require Class I flammability performance include healthcare facilities, and new construction correctional facilities. Class II performance, where the CRF is between 0.22 and 0.45 W/cm2, is typically required for day care centers, hospitality, existing correctional facilities and apartment buildings. Carpeting and rug applications on ships typically require a CRF value of at least 0.80 W/cm2.36 The radiant panel test has been adopted by several building codes and accepted by both the American Association of Testing and Materials (ASTM E-648) and the National Fire Protection Association (NFPA-253).37 The radiant panel test is applicable only to corridors. Carpeting installed in rooms or other locations should be governed by the pill test, FF 1-70. The flammability test detailed in the 49CFR571.302 is used by the automotive industry to measure flame spread. Testing can be conducted in either horizontal or vertical mode depending on the use of the fabric being tested. Per the standard, acceptable flame spread is four inches per minute or less.38 Compliance with this standard is required for automotive floor coverings as well as other materials used in the occupant compartments of motor vehicles. The most prevalent test method for smoke generation is the NBS Smoke Density Chamber test referenced as ASTM E-662 and NFPA-258.39 In this test, smoke density is measured by inference based on a reduction in light transmittance. The smoke density can be measured in either flaming or non-flaming mode. Some governmental agencies reference smoke density performance in specifications despite disclaimers stating its intended use for research purposes only.40 Oxygen Index (OI) is defined as the minimum oxygen concentration required to support candle-like combustion of plastics.41 The test method described in ASTM D2863 is used to determine the ignition resistance of a plastic material. For carpet backing compound flammability evaluation, a compound film is cast, dried, and tested in accordance with the

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standard. This method has the benefit of testing the backing compound without the carpet. In general, a higher oxygen index indicates better ignition resistance properties. Some non-regulatory tests such as the cone calorimeter42, Thermal Gravimetric Analysis (TGA), and Differential Scanning Calorimetry (DSC), yield more scientific information but don’t always address physical phenomena that sometimes occur during combustion such as dripping.43 No one flammability test covers all polymer flammability phenomena. Ignition Resistant Latex Development Halogenated latices have been used for many years in the carpet industry, primarily for improved ignition resistance. When first developed, these tended to have lower solids levels and result in reduced carpet physical properties when compared to carboxylated styrene butadiene latex products. Over time, recipe adjustments were made in an effort to improve the performance of the halogenated latices. As recently as early 2004, halogenated latex was limited to high filler load residential carpet applications or commercial carpet lines operated at low line speeds. A new halogentated terpolymer latex was developed that addressed these application deficiencies. The terpolymer latex has chlorine reacted into the backbone of the polymer that provides a “built in” level of ignition resistance. This inherent ignition resistance enables the formulator to displace some or all of the alumina trihydrate with less costly calcium carbonate filler which may result in substantial compound cost savings. The addition of ATH to a formulation based on halogenated latex further improves ignition resistance of the compound. The presence of chlorine in the polymer backbone also allows the use of an antimony synergist without the addition of expensive bromine containing additives or concerns associated with additives such as loss or leaching over time The oxygen index of compound films made with various substitution levels of ATH for calcium carbonate using both standard SB latex and halogenated latex can be used to compare ignition resistant formulations. Figure 4 illustrates the impact of ATH level and latex type on oxygen index in typical 600 Load precoat compound films. The use of an antimony synergist further improves the ignition resistance of the compound.

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600 Load Precoat CompoundIgnition Resistance Comparison

20253035404550

0 200 400 600

ATH Load

Oxy

gen

Inde

x (%

)

SB Latex

Halogentated Latex

Halogenated Latexwith Antimony

Figure 4. Filled Film Compound Oxygen Index

Several critical recipe parameters were adjusted to increase the latex solids level, improve the wet property retention, and soften the hand of the final latex product. Solids on the new latex were increased from 51% to 57%. The higher percent solids in the latex allows the final solids of the compound to increase thereby minimizing blistering in lower filler load compounds used specifically in unitary style commercial carpets. Blistering is an aesthetic defect on the back of the carpet caused by case hardening of the compound surface and continued drying of the residual moisture within the compound. When the water removal rate exceeds the maximum diffusivity of water though the case-hardened layer, a blister is formed. Increased compound solids minimize the amount of blistering and can allow the use of higher air temperature in drying and subsequently higher throughput. The wet strength of the latex and the polymer tensile and elongation properties were improved to optimize the balance between carpet strength and flexibility. Further compound formulation development continues in residential carpet applications to balance carpet flame retardancy, coating cost, and physical properties. In several carpet applications requiring increased ignition resistance, the high-solids halogenated latex product has demonstrated proven performance at low total system cost. Summary Federal standards govern the flammability of carpet produced in the United States in addition to many local building and fire codes. Carpet manufacturers often find it necessary to improve the ignition resistance of their products with the addition of certain types of flame retardant additives and/or synergists to the carpet backing compound. Combustion of polymers involves heating, pyrolysis, evaporation, ignition, oxidation, and free radical propagation. Most effective ignition resistance mechanisms for carpet include cooling, oxygen reduction, and free radical elimination. The most common flame retardants in used latex carpet backings are ATH and halogens. Antimony trioxide is a popular synergist used in conjunction with halogen. The development of a high solids,

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inherently ignition resistant terpolymer latex for both commercial and residential carpet backing applications has given manufacturers a cost effective option for improving carpet ignition resistance.

References 1 “Flammability and Carpet Safety.” The Carpet and Rug Institute November 1988. <http://www.carpet-rug.org/technical_bulletins/9811_Flammability_and_Carpet_Safety.pdf> 2 Mischutin, V. “A New FR System for Synthetic/Cellulosic Blends.” Journal of the American Association of Textile Chemists and Colorists Vol 7, No. 3. March 1975. 3 Ginzburg, V.V., Moore, J.D., and Zhang, M., “Dow Internal Report” 2003 4 Ginzburg 5 Reinke, C.F., ““Dow Internal Report” 1970 6 Petrella, R.V., “Dow Internal Report” 1986 7 Reinke 8 Pumpelly, C.T., “Flame Retardant Polymers; The American Scene,” Trans. J. Plastics Inst. Jan 1967 9 Mischutin 10 Reinke 11 Kernstock, J.M. “Dow Internal Report” 1996 12 Kernstock 13 Ginzburg 14 Morgan, A.B., Worku, A.Z. “Dow Internal Report” 2003 15 Spears, D.A., “Dow Internal Report” 1993 16 Spears 17 Birnbaum, L.S. and Staskal, D.F. “Brominated Flame Retardants; Cause For Concern?” Environmental Health Perspectives Vol. 112, No. 1. (2004). 18 Birnbaum, 19 Birnbaum, 20 Kernstock 21 Kernstock 22 Morgan 23 Ginzburg 24 Morgan 25 Farrell, M., “Dow Internal Report” 2005 26 Morgan 27 Kernstock 28 Morgan 29 Morgan 30 Kernstock 31 “Carpet and Rugs Flammability Tests.” The Carpet and Rug Institute March 1999. <http://www.carpet-rug.org/technical_bulletins/9903_Carpet_&_Rugs_Flammability_Tests.pdf> 32 16CFR1630 “Standard for the Surface Flammability of Carpets and Rugs” 33 “Carpet and Rugs Flammability Tests.” The Carpet and Rug Institute March 1999. <http://www.carpet-rug.org/technical_bulletins/9903_Carpet_&_Rugs_Flammability_Tests.pdf> 34 “Flammability and Carpet Safety.” The Carpet and Rug Institute November 1988. <http://www.carpet-rug.org/technical_bulletins/9811_Flammability_and_Carpet_Safety.pdf> 35 Radiant Panel: ASTM E648-04 “Standard Test Method for Critical Radiant Flux of Floor Covering Systems Using a Radiant Heat Source” 36 46CFR116.423 “Furniture and Furnishings” 37 “Flammability and Carpet Safety.” The Carpet and Rug Institute November 1988. <http://www.carpet-rug.org/technical_bulletins/9811_Flammability_and_Carpet_Safety.pdf> 38 49CFR571.302 “Flammability of Interior Materials”

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39 Smoke Density: ASTM E662-03e1 “Standard Test Method for Specific Optical Density of Smoke Generated by Solids Materials” 40 “Smoke Generation,” The Carpet and Rug Institute November 1998. <http://www.carpet-rug.org/technical_bulletins/9811_Smoke_Generation.pdf> 41 Oxygen Index: ASTM D2863-00 “Standard Test Method for Measuring the Minimum Oxygen Concentration to Support Candle-Like Combustion of Plastics (Oxygen Index)” 42 Cone Calorimeter: ASTM E1354-04a “Standard Test Method for Heat and Visible Smoke Release Rates for Materials and Products Using an Oxygen Consumption Calorimeter” 43 Morgan