R. C. NAMETZ
Flarme-Retarding Synthetic Textile Fibers Synthetic fibers and their relation t o flame retardancy
(omitting Sunday), about ten every day pass to heaven through flames in this very island of Great Britaintheir deaths are chiefly (caused) through carelessness of parents” (2). Even these are rather contemporary notations concerning the flammability hazards of textile materials. Sabattini in 1638 recognized the flammable hazard of painted canvas scenery from theaters and recommended clay or gypsum be incorporated in the paint used. A patent (3) was issued in England in 1735 for flameproofing cotton with a mixture of alum, ferrous sulfate, and borax, while Gay Lussac, the famous French chemist, in 1821 flame-retarded linen and jute with a mixture of ammonium phosphate, ammonium chloride, and borax (4). Thus, the hazards associated with combustion of textiles, principally cellulosics, have been recognized for a very long time. However, the need for flame retarding synthetic fibers has not been fully recognized. As late as 1966, a review on Fire Resistant Textiles failed to point out the hazards associated with certain synthetics (5). Quoting from the review, “Textile fabrics made from wool, silk, and protein-like synthetic polymers are not considered sufficiently combustible, for the most part, to warrant the need for flame retardant finishes.” Perhaps the reason that the new synthetic fibers were not considered very hazardous was that these fibers are produced from thermoplastic polymers which upon ignition melt and carry away the flame. Recent modification of these fibers by blending of nonmelting fibers such as cotton, rayon, etc., have considerably altered this concept. I t has been established that most synthetic polymers burn rather well when suspended by a carbonaceous grid work formed from combustion of cellulosic or nonmelting materials (6). This has been termed the “scaffolding effect.” Kruse illustrated the burning characteristic of a wide number of single and multicomponent fabrics, both with and without flameproofing finishes, and concluded that the ability and technique necessary to render a given multicomponent blend flame retardant was based entirely on the percent composition of the blend and on this scaffolding effect.
I
he flammability hazard of textile materials has Treceived some recognition for a considerable period
of time. As evidence of this, the following editorial comment appeared over 100 years ago in the July 1861 issue of Scient@ American concerning the untimely death of the wife of America’s poet laureate by a clothing fire: “The public has been painfully startled by the death of Henry Wadsworth Longfellow’s wife which occurred in Cambridge on the tenth instant. Mrs. Longfellow was seated in her library and was in the ,act of making seals with sealing wax. A bit of paper caught fire and before the blaze could be controlled, she was painfully burned. The dresses commonly worn by women in warm weather are composed of muslin and such-like flammable materials. Although we have urged the preparation of ladies dresses with nonflammable material, we trust that the subject of safety clothing will receive more attention from ladies. Their own sense demands this.” ( I ) . T h e British writer Thomas De Quincy displayed his concern over deaths resulting from apparel fires 20 years earlier as follows : “Three thousand children per annum-that is
R. C. Nametz is Section Head, Organic Research, with the Michigan Chemical Cor@., St. Louis, Mich. T h e paper was presented as part of the Symposium on Flammability Characteristics of Polymers, Oakland University, June 16-20, 1969, @onsored by the University of Detroit. AUTHOR
VOL. 6 2
NO. 3
MARCH 1970
41
Kruse further proposed a rule that “the behavior under combustion of a blended fabric is practically identical to that of its main component when the latter represents not less than 8570 of the total. Thus, in order to render fabric of this nature flameproof, it is only necessary to treat the main component. If, however, the blend consists of more than 15% of the auxiliary component, the latter must be flameproofed also.” Kruse and coworkers used two test methods for evaluating the burning characteristics of fabrics. I n one test, 4 cm by 35 cm specimens that were suspended to hang freely were ignited a t the lower end with a 4-cm luminous Bunsen flame. Time elapsing to self-extinguishing or to complete combustion was noted. The second test method used was DIN 53906 (German vertical combustion test). I n this test, fabric specimens 8 cm wide by 20 cm long were held in a frame, and ignited in a vertical position a t the lower end with a 4-cm luminous Bunsen flame for periods of 4 to 14 sec depending on fabric weight. After ignition, measurements were made of time of burning, afterglow, and length of char. U p until recent times, cotton, cellulosic derivatives, silk, and wool dominated the textile industry market and most of the effort for development of flame retardants was devoted to cotton and its derivatives. As synthetic or man-made fibers (especially the acrylics) entered the marketplace, more and more articles and patents began to appear which were concerned with reducing the flammability of synthetic materials. Much of the impetus for conducting work on flame-retarding textile materials has been generated by enactment of federal, state, and local legislation, as well as concern by various textile organizations such as thv American Association of Textile Chemists and Colourists (AATCC). In 1953, the Federal Flamniable Fabrics Act was passed following occurrence of a number of burn accidents involving “torch sweaters” made of brushed rayon: and highly flammable cowboy chaps. The Act, based on a standard established by the AATCC banned interstate shipment of textile materials of an unusually hazardous nature.
PUBLICLAW 88 8 3 CONGRESS ~ ~ 6/30/53 “To prohibit the introduction of movement in interstate commerce of articles of wearing apparel and fabrics which are so highly flammable as to be dangerous when worn by individuals, and for other purposes.” The Act left untouched most of the flammable material that goes into everyday clothing and household furnishings. In late 1967, a new amendment to the law was passed which was designed to prevent injuries and deaths from fabric fires by bringing other personal and household fabrics under the law.
PUBLIC LAW 90-189 ~ O T HCOSGRESS 12/14/67 “To amend the.pammable fabrics act and to increase protection afforded consumers against znjuriousflammable fabrics.” 42
INDUSTRIAL AND ENGINEERING C H E M I S T R Y
The amendment was designed to prevent cases such as the one reported from Seattle in which a 2-year-old girl was burned over 85% of her body with a nightgown ignited by flames from an open heater or that of an 18month-old girl in northern Ohio who received 2nd and 3rd degree burns over her body when her jacket was ignited by a n electric range burner. Just how serious a public health problem it is in the United States in number of persons burned from textile products has not been known accurately. However, a t the second annual meeting of the Information Council on Fabric Flammability last December, some startling preliminary statistics were presented by A. F. Schaplowsky, Acting Chief of Injury Control Program, H E W (7). Yearly deaths from flammable fabrics
4,000
Total burns each year (medical attention or activity restricted) 2 million Bed cases
300,000
Burn cases involving fabric ignition
175,000
Burn cases involving clothing ignition
150,000
Bedclothing ignition injuries
20.000
Estimated economic losses
>>$400 million
Under the new amendment, the Department of Health, Education, and Welfare will undertake the assembly of the facts on deaths, injuries, and economic losses resulting from the accidental burning of products, fabrics, or related materials. Physical Factors Affecting Flammability of Textiles
Textiles are made up of fibers interlocked or bonded into sheets that are relatively thin in relationship to width and length. They are normally porous and flexible. I t is this porous nature that makes them readily ignited by a flame and once ignited, allows oxygen to reach the site of combustion. Some fabrics are much more tightly woven than others. I t has been shown by Richards (see Figure 1) that as the area/ volume ratio of fabric is increased in a fabric, ease of ignition increases, and usually the linear burning rate will also increase (8). The main reason for this is that there is less weight of fiber in a given volume to heat up to ignition temperature and air has ready access to feed the flames. A good example of this is the burning characteristic of a tightly woven fabric in comparison to a napped or high piled fabric. Sayers has reported an exception to this in the case of combustion of certain synthetic fibers such as polypropylene ( 9 ) . It was found that a light weight fabric of about 3 oz/yd was self-extinguishing while a heavier one of 6 oz/yd burned. It was theorized that with the heavier fabric, the molten polypropylene didn’t detach itself carrying the flame with it as it did with the lighter fabric. This ability of thermoplastic fibers to melt in the igniting flame or to drip leads the synthetic fibers to be classified as less flammable than the nonmelting fibers such as the cellulosics. When these thermoplastic synthetic fibers are blended
bustion processes of the synthetic polymers will become much better understood. An oversimplified version of combustion of any polymeric material is as follows: Heat from a source of ignition raises the temperature of the polymer above its decomposition point yielding flammable, volatile polymer fragments which mix with air and are transported to the flame front. Then combustion occurs. Heat from combustion continues to generate flammable gases and burning continues. Table I lists the burning behavior of many textile fibers currently used (72, 90).
6
m
n z
0 0 W
m 4 I
w
r: + L
L
Z
2 4 6 8 WEIGHT OF FABRIC OUNCES/SQ YD.
-
Figure 7. Ignition time us. fabric weight
with nonmelting fibers such as the cellulosics, the molten polymer is not permitted to drip away and the combined system is flammable. For example, nylon and glass fiber blend is more flammable than nylon alone. Nylonrayon blends used for automotive upholstery fabric are much more difficult to flame retard than nylon alone. I t is the so-called scaffolding effect in operation as discussed earlier. Nylon stiffened with melamine resin is reported to form a strong char and to burn readily while a urea resin, a poorer stiffener, has a much lower burning rate because it melts on ignition and drips away with molten nylon (70). Another good example is polyacrylonitrile fiber which when heated is converted into a solid ladder-type polymer which is nonflammable but also nonmelting (77). I t is for this reason that some acrylic fibers are quite flammable-that is, formation of the “black polymer” provides opportunity for the volatile, flammable decomposition products evolved on pyrolysis to mix with air and burn. Another factor which is of considerable importance in flammability of textiles is the position or location in which textiles are employed. I t is fairly obvious that a given textile covering a floor or table is considerably less hazardous than if employed as drapery or apparel. Vertical orientation and number of exposed surfaces are significant factors in heat convection. Chemistry of Flammability of Textiles
Much information has been generated concerning the combustion process involved with cellulose. However, very little has appeared regarding the chemistry of synthetic fibers. Much has been published on thermal decomposition or pyrolysis of synthetic fibers but very little has appeared concerning the chemical processes involved-most generally they are termed “complex” and not well understood. With increased emphasis on overcoming the flammability hazard of new fibers and the development and application of modern analytical tools such as gas chromatography, rapid scan infrared, time-of-flight mass spectrometry, and differential and therniogravimetric analysis, it is anticipated that com-
Flame-Retarding Fibers Based on Acrylonitrile
“Acrylic fibers” are recognized by the Rules of the Federal Trade Commission as a manufactured fiber in which the fiber-forming substance is any long chain synthetic polymer composed of a t least 85y0 by weight of acrylonitrile chain (-CH2--CH-). Acrylic fibers
I
C=N shrink when heated, decreasing the opportunity for accidental ignition. However, once ignited they burn vigorously, especially those of high pile or loose weave construction, producing clouds of black smoke. The acrylic fibers are associated with warmth and light weight, durability, a luxurious and soft hand, light Table I .
Burning Characteristics of Textile Fibers Ignition temp “C (9)
Fiber
Flammability
400
Cotton Rayon Acetate Nylon 6 Nylon 66 Triacetate Acrylic Modacrylic Polyester Polypropylene Wool
PVC and polyvinylidene chloride
Burns readily with char formation, afterglows 420 (73) Burns very rapidly with char formation, no afterglow Burns, melts ahead of flame 530 Supports combustion with difficulty, melts 532 Does not readily support combustion, melts 540 Burns readily, melts ahead of flame 560 Burns readily with melting and sputtering .. . Melts, burns very slowly 450 (13) Burns readily with melting and soot 570 Burns slowly 600 Supports combustion with difficulty, melts ahead of flame , . Does not support combustion
.
All fibers yield gaseous products between 500-800°C that burn except P V C and polyvinylidene chloride. H20 ethanol, COZ,CO, hydrocarbons, and cyclopentanone Polypropylene -.+ pentane, pentene, hexene, butane, propylene, and ethylene Acrylics 6 alcohols, hydrocarbons, ketones, H C N -I- “black polymer” PVC & polyvinylidene -.+ HCI, hydrocarbons chloride Nylon
-P
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43
fluffy construction, retention of shape, resistance to sunlight, weather, oils, and chemicals. They are easily dyed with a wide range of colors and, therefore, find broad markets. One of the major end uses of acrylic fiber is carpeting, where luxurious texture and easy care are very important. Sweaters, slacks, dresses, drapery, and upholstery are also major outlets for textile fabrics based on acrylic fiber. Of all the synthetic fibers in the marketplace today, acrylic fibers have received the greatest attention in trying to develop improved resistance. T h e approaches which have been used to gain flame resistance can be classified as follows: 1; Copolymer or blend of polymers 11. Finish 111. Additives IV. Chemical modification
I.
Copolymer or Blend of Polymers I n this technique monomers bearing a flame-retardant element or elements are copolymerized with acrylonitrile, or a polymer prepared from a flame-retardant monomer is blended with polyacrylonitrile. Fibers now on the market containing less than 85yo,but not less than 35y0 acrylonitrile, are called “modacrylic” fibers. Modacrylic fibers usually have much greater flame resistance than acrylic fibers, principally due to the content of vinyl chloride or vinylidene chloride in the polymer structure. These monomers have been studied extensively to modify acrylic fibers. T h e copolymerization of vinyl chloride with acrylonitrile in the extent of about 20% or greater imparts greatly improved flame retardancy. However, it has been found that the resulting fibers have such low “sticking temperatures” and high shrinkage a t elevated temperatures that they were unsuitable for most textile applications. For example, when acrylonitrile is copolymerized with 20-407, vinyl chloride, the flame resistance is greatly enhanced, but the sticking temperature is below 150 “ C and shrinks considerably in boiling water compared to 200 “ C for polyacrylonitrile fiber with no modifier and shrinkage of about 57, in water. Blends of polyacrylonitrile and polyvinyl chloride or polyvinylidene chloride do not produce good fibers. T h e blends are incompatible and present many difficulties in spinning--e.g., immiscible droplets can form in the spinning dope causing fiber segmentation. Coover and Dickey (74) found a technique for copolymerizing vinyl chloride or vinylidene chloride which is claimed to circumvent the above difficulties. By their method, vinyl chloride or vinylidene chloride is first emulsionpolymerized, and acrylonitrile is then added to the socalled “live polymer” a t once with more catalyst and the polymerization continued. Thus, a polymer such as the following is secured when A and B represents repeating units of (-CH-CH-) and (-CH-CH-), respec-
I
c1
I
Csn.
tively, AAAAAABBBBRBBB, etc. 44
I N D U S T R I A L A N D ENGINEERING
CHEMISTRY
The resulting polymers were found to be readily soluble in the known solvents used for spinning polyacrylonitrile and the spun fibers retained most of the properties of the polyacrylonitrile. In addition, they possessed much improved flame resistance. Wooten and Shields (75) developed a continuous method for graft polymerizing vinyl or vinylidene chloride and acrylonitrile onto a n X-alkylmethacrylamide polymer, The graft polymers could be prepared from either a n isolated dead preformed polymer or a “live” polymer. T h e resultant graft polymers were characterized by a higher softening point, increased compatibility with other homopolymers or copolymers in solution in the spinning solvents, greatly improved dyeability, moisture absorption, elongation, and tensile characteristics. A method designed to provide fiber-forming acrylonitrile polymers which would yield fabrics, rugs, etc. that, when ignited, would not produce molten tarry globules as a cornbustion product, but a firm ash, was obtained by Hobson (76). This method consists of mixing about 8040% of: (1) a polymer blend of a copolymer of acrylonitrile and another monomer such as vinyl acetate, with a copolymer of acrylonitrile and vinyl pyridine with (2) a chlorine containing polymer such as polyvinyl chloride, polyvinylidene chloride or a copolymer of greater than 807, vinyl chloride or vinylidene chloride and another monomer. L7inyl comonomers lower resistance to heat. For this reason their content is limited in a fiber. Vinylidene chloride is different--i.e., the copolymers with acr) lonitrile have better heat resistance (at least up to 30% vinylidene chloride). T h e glass transition temperature of pure polyacrylonitrile or with small amounts of vinyl acetate is raised from 87 “ C to 110 “ C with 7y0vinylidene chloride and to 135 “ C with 307’ vinylidene chloride. The high glass transition temperature means good resistance to deforming stress a t high temperatures. However, the dye receptivity of such fibers is found to be poor, therefore, their use is very limited. T h e use of two other monomers with vinylidene chloride was proposed (77). Types of monomers proposed in order to yield flame-retardant fibers with good dye receptivity and high softening temperature were those having bulky side groups with steric hindrance. These groups influence the lateral order of the macromolecules in the fiber, reducing the compactness thereof, and thus making the groups having affinity for dyestuffs more easily accessible to the latter under normal dyeing conditions, For example : \in)-1 acetate, ethyl acrylate, iV-ethyl acrylamide, etc. ( 3 4 % ) . T h e other type of monomer proposed in order to aid dye receptivity was that having acid functional groups, such as itaconic acid, fumaric acid, maleic acid, etc. (0.5-2.070). Other patents describe the use of vinylidene chloride with monomers such as styrene or methylrnethacrylate (78) or with acrylainide and vinyl acetate (79). Good dyeability and low dry-heat shrinkage are claimed. As a result of the superior flame-resistance properties of bromine over chlorine, vinyl bromide has been used in copolymers with acrylonitrile (20-22).
I t was discovered that fibers containing 4% bromine and 2Oj, antimony oxide were self-extinguishing and easily dyed (20). I t could be surmised that fibers would probably have high softening temperatures and, because of the bulky bromine group, compactness of the macromolecules would be reduced leading to better dye receptivity. Another logical monomer for imparting flame resistance to acrylonitrile polymers is a-chloroacrylonitrile (23, 24). I t is claimed that as much as a 40% improvement is attained over polyacrylonitrile in dye receptivity when this monomer is copolymerized with acrylonitrile. A novel type of monomer based on hexahalocyclopentadiene has been studied by Marvel and Kovacs (25). Hexachloro- or hexabromocyclopentadiene was condensed with acrylic acid to form 1,4,5,6,7,7-hexaacid. X = halobicyclo- [2,2,1]-5-heptene-2-carboxylic Br, C1
X
+
CH2=CH-C0,H
+
x@cozH X
X
x x
X = Br, C1
The acid was then used to transesterify vinyl acetate to form its vinyl ester.
9
X
II "@"" X + CH&-OCH-CH,
--P
X
4.
Monoallyldialkyl phosphates (29) R = 2-chloroethyl or 2-bromoethyl R' = allyl or methallyl R'P(O)(OR)2
(R'O)(RO)zP=O
5. Dialkyl-2-cyanopropene-3-phosphonates(30, 37) OR CH2=C-CH2-P
I
/I \
0 OR
CN 6.
Dialkyl-2-halopropene-3-phosphonates (32) OR CH,=C--CH2-P
I X
II.
/
/
R
ll\
X
= 1-5C = Br or C1
0 OR
Finish
This method of imparting flame resistance to acrylonitrile fibers or textiles involves treatment of the fiber or fabric with flame-retardant finishes. These are enumerated below : Ammonium sulfide or polysulfide (aqueous solution) dried (33) Phytic acid HCHO urea (aqueous solution) dried then cured (34) Ammonium phosphates, urea, urea derivatives of esterified melamine resins (35) Tic14 - Sb203 reaction product (36) Urea, formaldehyde, and ammonium bromide (37) Hydroxylamine salts with methylolated melamine (38)
+
+
X&C02CH=CH, X
111.
x Copolymers with acrylonitrile were prepared. I t was found that when X was C1, copolymers were more readily formed than when X was Br. However, it was also found that nonflammable films were obtained with about 10% bromine content while with chlorine it was necessary for the films to contain 25% chlorine to become nonflammable. Phosphorus-containing monomers for copolymerization with acrylonitrile has been studied to a considerable extent with the objective to impart flame resistance. These monomers are generally allyl or vinyl esters of phosphoric or phosphonic acid. 1. Alkyl esters of allyl phosphonic acids (26) CH-CHCHzP(0) (0R)z 2.
Bis (2-chloroethyl)vinylphosphonate (27) (ClCH2CHzO) 2P(O) CH=CH2
3.
CY- and
P-Dialkylphosphono acrylic acid esters (28)
0
11
CHt=C-COR
I
P (OR0 2
0
I/ I
R~O-P-CHH=CH-CC-OR
0R'
I1
0
Additives
I n the additive approach to flame-retarding acrylic fibers, the additive is dissolved, suspended, or dispersed in the spinning solution with the polymer. Usually either of two solutions are used for spinning, dimethyl formamide, and aqueous zinc chloride (50-60%) or sodium thiocyanate solution. The solution, suspension, or dispersion, is then extruded through very small orifices into a bath containing a reduced concentration of the solvent or salt in water. This coagulates the polymer which is then picked up, washed, stretched, dried. Most of the additives that have been considered as flame retardants for polyacrylonitrile fibers are esters of phosphorus that usually contain halogen in the alkyl side chain. Tris(dibromopropy1)phosphate shows exceptional compatibility with polyacrylonitrile and is a very effective retardant (39). Certain nonhalogenated phosphates have been claimed to provide good flame resistance and quite unexpectedly were found to be retained in the polymer during wet spinning (40). This is unexpected since a phosphate such as tricresyl phosphate is normally extracted from the polymer in substantial amounts during wet spinning. Trialkyl phosphates, particularly found useful, contained 6-1 6 carbons in the alkyl group, are added in 5-3Oy0 to the polymer to obtain flame resistance. Brominated telomers formed from halomethanes and VOL. 6 2
NO. 3
MARCH 1970
45
unsaturated phosphates represent interesting compositions to reduce flammability of polyacrylonitrile fibers (47). An equation for their preparation is given below : (CH2=CHCH2O)aP--;O
20
15
peroxide + CCI4 ------+ catalyst
c1
0
I
I1
8 c
Brz
C H 2 - C H - C H 2 0 - ~ - ( ~ ~ ~ 2 ~ ~--+ = ~ ~ 2 ) 2 0" I O N -
5m
cc13
0
0
c1
Br
I
I
C13CCH-CH-CH20P(OCH2CH-CH2Br)
5 2
/I
0
0 Another interesting phosphate structure utilized for flameproofing is 2-cyanoethyltetramethyldiamidophosphate (42). This may be prepared by condensing 2cyanoethanol with tetramethyldiamidochlorophosphate in the presence of a tertiary amine. CH3)2N
\
P-C1
/il
+ HOCHSCHSCN * R3N
CHS)*iY 0
Bromine containing phosphonates in combination with insoluble calcium salts of phosphoric acids are claimed to provide synergistic effect on flame retarding fiber-forming acrylonitrile polymer (43). Varying percentages of bis(1,Z-dibromopropy1)- and 1,Z-dibromopropanephosphate and tricalcium phosphate were incorporated into polyacrylonitrile by dispersing them into aqueous polyacrylonitrile spinning solution (zinc chloride solution). Films about 0.01 inch thick, 3 inches long, and 7/8 inch wide were cast, washed free of zinc chloride, stretch oriented and dried. The films were clamped in horizontal position and ignited a t one end with a paper match. The time in seconds required for the film to burn 1 in. past an initial 1/4-in. reference mark was recorded. Figure 2 shows that a polymer film containing 157, of the phosphonate burned 1 in. in 17 seconds while a film containing 1570 of calcium phosphate burned 1 in. in 9 seconds. However, certain combinations of tricalcium phosphate and the organic phosphonate employed a t the 15% level were found to be self-extinguishing and did not burn 1 in. past the reference mark. Halogenated fatty acid esters, especially those with a long chain-containing bromine, have been found useful as flame retardants for polyacrylonitrile fibers (44). 46
INDUSTRIAL A N D ENGINEERING CHEMISTRY
0 5 IO 15 20 BIS (BROMOALKYL) BROMOALKYLPHOSPHONATE, O'/ 0 3.5 ZO 10.5 14.0 BROMINE,%
Figure 2. Flame retardant acrylic jibers, synergism of additioes
Similarly, the amides of the corresponding acids were investigated and found to provide flame resistance (45). Low-molecular-weight polymers formed by salt-condensing epihalohydrins have received attention (46, 47). Molecular weights of the polyepihalohydrins below 1200 were found desirable to secure good compatibility. I t was further found that a synergistic effect could be obtained using these polymeric additives with insoluble calcium phosphates or antimony oxide. T h e flameproofing mixtures were found not to be extracted from the polyacrylonitrile polymer during wet spinning, and flame resistance was retained on repeated laundering of fabrics prepared from the fibers. Finally, polybromochlorocyclohexanes in combination with insoluble calcium phosphates are claimed to give a synergistic flame-retardant combination in polyacrylonitrile fibers (48). This combination is applied as a finely divided dispersion in the solution of polyacrylonitrile in highly concentrated salt solution (5060% aqueous ZnCls). A summary of the additives investigated are : Tris(dibromopropy1)phosphate (39) Trialkyl phosphates of 6-l6C in alkyl (40) Telomers of bromo- and chloromethanes and unsaturated phosphates that are brominated (47) 2-Cyanoethyltetramethyldiamidophosphate(42) Bromine containing phosphonates an insoluble calcium phosphate (43) Esters of polyhalo fatty acids (44) Brominated ;17,iV-dialkylamides of unsaturated fatty acids (45) an insoluble calcium phosphate Polyepihalohydrin or antimony oxide (46,47) Polybroinochlorocyclohexanes (48) Halogen containing polymeric phosphonates (49) Salts of metals (>bivalent) (50)
+
+
1V. Chemical Modification Only one reference was found to this approach. Rogin a n d coworkers copolymerized acrolein with acrylonitrile to introduce aldehyde groups in the macromolecule (57). Flame resistance was then imparted by reaction of the aldehydic groups with dimethylphosphite :
(-CH2-CH-),(-CH2-CH-).
I
C=N
+
I c=o I H
CH30
\
X
P-H
--t
(-CH2--CH-),-
/I I
CH30
II
C=N
0
(-CH2--CH-)
,-(CH2-CH-)x
I
I
c=o
H-C-OH
H
O=P(O CH3)2
I
I
When the starting polymer contained greater than 6% aldehyde groups, it was soluble in dimethylphosphite. It was found that 3.5% phosphorus produced a fiber that was noncombustible. However, because the hydroxy phosphoric acid groups are very susceptible to hydrolysis, it was necessary to modify the reaction using a n amine such as diethylamine. T h e polymer obtained had the following structure :
(- CH2-C H-)
I
C=N
(- CH2-C H-)
,-X
I c=o I
H
(-CH2-CH-),
I
HC-N(C2HJ2
I
O=P (0CH3)2 Susceptibility to hydrolysis was eliminated as evidenced that after 5 hours boiling with water the phosphorus content of a fiber remained nearly constant (9.0570 to 8.55%). T h e treatment is accompanied by a slight decrease in durability but a considerable increase in stretchability over polyacrylonitrile fibers. Flame-Retarding Nylon Fibers
Nylon is defined as a manufactured fiber in which the fiber-forming substance is any long-chain synthetic polyamide having a recurring amide group (-C-NH-)
II
0 as a n integral part of the polymer chain. Polyamides are usually made by condensing a dibasic acid such as adipic acid with a diamine such as hexamethylene diamine with removal of water or by poly-
merization of a caprolactam. T h e polyamide formed is melt-spun into fibers and oriented after cooling to give the desired properties for each intended use. Generally, the polyamide fibers are sharp melting. If a fabric of nylon fiber is ignited in a vertical position, the flame does not propagate to any appreciable extent but the polymer melts a n d drips away, carrying the flame with it. Nylons are usually said to be self-extinguishing for this reason. A different situation exists altogether when nylon fiber blended with a nonmelting type of fiber such as cotton or rayon is ignited. T h e blends readily propagate a flame. This is explained by the fact that the nonmelting type of polymers burn to form a carbonaceous grid work which holds the melted nylon in place so that combustion can occur. One of the major areas of application for nylon is in automotive and furniture upholstery. I t is anticipated that the need for better flame resistance for these applications will be a definite requirement in the not-too-distant future. Most generally, nylon or nylon-rayon blends which are used in these applications require a flexible backcoating which prevents unraveling and fraying a t the seams during sewing and use. Incorporation of a flame retardant in the backcoating of upholstery type of fabric offers one means available for imparting flame resistance. I t has been found that the usual flame retardants for many other polymer systems such as halogen compounds, inorganic, and organic phosphates do not function very efficiently in flame-retarding nylon or nylon blends. It is believed that a n entirely different mechanism is in force in the burning of nylon and, hence, a n entirely new concept in a flame retardant must be developed for nylon. T o date, no truly effective flameretardant finishes for nylon have been developed. It is anticipated that the better appproach to development of a satisfactory solution to flame-retarding nylon and nylon nonmelting fiber blends will be to find a flame retardant that can be incorporated in the molten nylon when it is spun to yield a durable treatment. T h e flame retardant developed should be effective a t relatively low concentrations so that the excellent physical properties of nylon are not degraded to too great a degree by the inclusion of the flame retardant. When 6ne examines the technical literature on flameproofing of nylon or nylon blends it becomes readily apparent that only one method, namely fabric finishing or after treatment, has been proposed for conferring flame resistance. Many of these finishes utilized thiourea, formaldehyde condensates for supplying flame resistance. T h e launderability of such finishes is not very satisfactory. A tabulation of various treatments uncovered in a review of the literature is given below : Thiourea-formaldehyde resin (52, 53) Thiourea-aldehyde condensates (54) Thiourea-alkylene urea condensates with formaldehyde (55) Thiourea of thiourea-formaldehyde or oxamide (56) Alkylated dimethylolurea-methylola ted thiourea-thiourea resinous compositions (57) VOL. 6 2
NO. 3
MARCH 1970
47
+
Urea form ccndensation product thiourea-form condensate (58) N,N-bis(hydroxymethy1) ethylene urea thiourea latent curing catalyst (59) Aldehyde urea in presence of bisulfites (pH 7-9) (60) Formaldehyde oxidizing agent 5 100 OC (67) Organic amine ammonium bromide (62) Ammonium bromide aminotriazine-HCHO condensate (63) Ammonia-phosphorus trichloride reaction product (64) Dimethyloltriazinethiones and ethers (65) Sulfides antimony oxides (66) Urea condensate phenol condensate (67) PVC and polyvinylidene chloride Sb, Sb-Bi salts (68) Pyridine based polymers (from vinyl pyridines) in acid solution, dried, then treated with base (69) Polychlorinated benzenes microcrystalline wax (70)
+
+
+
+ +
+
+
+
+
+
Flame-Retarding Polyester Fibers
Although a limited amount of work has been reported concerning flame-retarding polyesters, we can now expect to see a considerable increase in frequency of publications in the near future. I t is anticipated that most of the effort will be devoted to rendering blends of polyester with cotton and other cellulosics flame retardant because this is the area of tremendous growth for polyesters. Further, the blending with nonmelting fibers has increased the flammable hazard of polyester significantly. I n 1968, man-made fiber consumption in the United States surpassed natural fiber consumption for the first time in history and the chief reason for the dramatic shift was due to a tremendous increase in polyester consumption against a significant decline in cotton consumption (71).
Man-made fiber consumed, billion Ib Natural fiber consumed, billion lb
1967
1968
4.1 4.7
5.0 4.6
Polyester staple and tow production jumped almost 225 million lb in 1968 from 563 to 776 million lb., while cotton declined from 4.41 to 4.24 billion lb. Polyester is defined as a manufactured fiber-forming substance in any long chain synthetic polymer composed of at least 85Y0 by weight of an ester of a dihydric alcohol and terephthalic acid (p-HO2C-CsH4-CO2H). I t is normally produced by transesterification of dimethyl terephthalate with ethylene glycol. Generally, the fiber is melt-spun from the polymer. Polyester fibers have the outstanding characteristics of high strength, high resistance to stretching and shrinkage, dye well, and have excellent resistance to most chemicals. Fabrics can be heat set and retain that shape through repeated washings. Some of the principal uses for fabrics based on polyester are in suits, slacks, shirts, dresses, and other apparel, home furnishings. T h e staple is used as nonmatting filler for sleeping bags, mattresses, automotive 48
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
cushioning, jackets, etc. The fiber is becoming increasingly important in the carpet and tire cord industries. T h e efforts to render polyester fiber or fabrics flame retardant are summarized below : Fabric coated with PVC, polychloroprene-chlorosulfonated polyethylene, polyurethane, natural rubber (72) Fabrics coated with PVC plastisol containing S b 2 0 3 and sulfide or oxide of bivalent metal or mixture of sulfide and salt of bivalent metal (73) Blends with cellulosic fiber treated with solution of condensed phosphoric acid and a quaternary ammonium hydroxide or amine and baking (74) Nonwoven fabric bonded by polymer mixture containing vinylidene chloride in one of polymers Sbz03 (75) Fibers embedded by layers in sodium silicate (76) Fibers treated with alcohols or polyether polyols a t elevated temperature in presence of nonvolatile mineral acid (77)
+
I t is anticipated that to obtain a satisfactory longrange solution to flame retarding polyester and blends, it will be necessary to develop and include in the melt prior to spinning compatible additives bearing flameretardant elements. Of course, the inclusion of these additives will be expected to have a minimal effect on the basic properties. I n addition, whenever blends with cellulosics are made, the treatment of cotton fiber with a permanent reactive flame retardant will probably be necessary. Flame-Retarding Polyolefin Fibers
Although a significant number of examples exist in the art concerning flame-retarding polyolefin molding compositions, very little has been published to date on flame retarding fibers from these polymers. With increased emphasis on the use of polyolefin fibers in carpeting of both conventional pile and in the indoor-outdoor type, in apparel fabric and upholstery applications, it is certain that this will change and effective flame retardants will be developed and patented. Olefin fibers are classified as those fibers produced from a t least 857, by weight of ethylene, propylene, or other olefin monomer unit except amorphous polyolefins that are elastomeric in nature. T h e largest fiber sold, of course, is polypropylene. This fiber is characterized by its excellent moisture resistance and chemical inertness. I t melts a t relatively low temperatures (325-335OF) and burns readily when ignited with dripping of the melt. I n the carpeting field, SBR latex is applied to the back of the carpet to add weight and dimensional stability. I t is this latex which enhances the propagation of flame when such carpeting is ignited. The usual technique used to impart flame retardancy to carpeting is to include a high halogen containing compound or compounds such as chlorinated paraffins or PVC along with antimony oxide in the backcoating.
From a longer range viewpoint, it is anticipated that effective flame retarding compositions will be developed that can be incorporated in the molten polypropylene prior to spinning. Such additives will be required to function so that the dyeability, and desirable physical properties will not be impaired to a large extent nor the already low softening temperature of this fiber be reduced further. Several references of interest concerning flame retardancy of polypropylene fibers or filaments have appeared. Polypropylene filaments having flame resistance were obtained by uniformly dispersing within the polymer certain halogen-containing compounds along with compounds to aid in their dispersion (78). One composition contained, in addition to the polymer, a chlorinated parafin, tris(2,3-dibromopropyl)phosphate, chlorendic anhydride and stearic acid. Another described contained dilauryl thiopropionate, Ional, @octylphenyl salicylate, Aroclor, and tris(2,3-dibromopropy1)phosphate or Phosgard B52RS (a bromine-containing polymeric phosphonate). The filaments were claimed to possess excellent textile quality with n o evident breakage or fibrillation. T h e results of flameretardant tests gave the filaments a good rating and it was found that little damage resulted in properties of the filament on exposure to sunlight for 6-9 months. Chlorophosphorylation of polypropylene fiber by first treatment with ozone in carbon tetrachloride and then phosphorus trichloride yielded polypropylene with improved receptivity to dyes having O H and NH2 groups (80, 8I ) . Phosphorus-containing polypropylene was prepared having phosphorus contents u p to 7%. Polymers with P contents of 4.7y0 or above were found to be self-extinguishing. Flame-Retarding Polyvinyl Alcohol Fibers
These fibers have received very little attention in the United States in regard to flame retarding them. They are not produced commercially here but have gained some importance in Europe. These fibers soften a t low temperatures but show unusually good chemical resistance. The Federal Trade Commission considers polyvinyl alcohol fibers (Vinal) to be any fiber possessing at least 50% by weight of the repeating unit (-CHzC H : OH-) in the macromolecule and in which the total of the vinyl alcohol units and any of the contained acetal units is at least 85y0of the fiber. Poly(viny1 alcohol) fibers (PVA) have been flanieproofed by converting a portion of the hydroxyl groups to acetals using chlorine and bromine containing acetaldehydes and benzaldehydes (82). Bromine was found to be a much more efficient flame-retardant element than chlorine. I t was further found that fibers treated with bromobenzaldehyde were not only superior in flame resistance to those treated with benzaldehyde, but were better in acid resistance, heat-setting properties, and elastic recovery. Phosphorylation of PVA fibers by a number of ways has been tried. PVA fibers in which 43y0 of the OI-i groups were acetalized were reacted with phosphorus
oxychloride in the presence of tertiary amines to yield partially phosphorylated fibers of reduced flammability (83). Various tertiary bases were studied but pyridine gave the best results as it accelerated the phosphorylation. A serious drawback to fibers treated in this manner is the rapid loss in strength and tenacity as phosphorus content necessary to gain flame resistance (3y0) is increased. Another phosphorylation technique has been described using urea and aqueous phosphoric acid a t elevated temperatures (84). No afterglow or flame resistance was a feature of resultant fibers. Orlov heated a dialkyl phosphonate with PVA in a solvent a t 120-130 " C to effect phosphorylation (85). The resultant polymers were found to be readily hydrolyzed by 1% sulfuric acid or 1% potassium hydroxide but showed some resistance to saponification under conditions used in laundering. Flame resistance was exhibited to a significant degree a t phosphorus levels of 270 or greater. T h e same worker also found flame resistance was enhanced by first dehydrating the fiber prior to phosphorylation (86). PVA fibers treated with H2P(OCH2CC13) to introduce 6 4 % phosphorus and 5-6y0 chlorine have been found to resist oxidation flame and bacterial action (87). Finally, PVA fibers, heat treated a t 224-226 "C, were etherified with dimethylolurea a t 80 "C and then treated with T H P C (tetrakishydroxymethylphosphonium chloride) to secure flame-resistant fibers containing phosphorus and nitrogen (88). Summary of techniques : Polymer acetalized with bromine containing aldehydes (82) Phosphorylation with P 0 C l 3 in presence of tertiary amine (83) Phosphorylation with urea and aqueous phosphoric acid (84) Phosphorylation with phosphonates (85, 86) HzP(OCHzCCl3) (87) Fibers treated with dimethylolurea, then T H P C (88) Tris( P-chloroethyl)phosphate or bis (P-chloroethyl)-pchloroethylphosphonate (89) Flammability lest Methods for Fabrics
Considerable effort has been devoted to the development of methods to determine the flammable hazards or flame spread of textile materials. Most of these methods were developed with cotton or other cellulosic materials in mind and generally ignore the phenomenon of dripping usually associated with 1OOyo synthetic fibers. However, because blends of the synthetic fibers with cellulosics and wool are being broadly used the usual methods for these materials will be recounted here. I n addition, considerable effort is being expended to develop more meaningful tests which will handle the manmade fibers, and a n account of these newer methods will be given. The earlier methods developed usually involved suspension of a preconditioned sample of a fabric of a VOL. 6 2
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given dimension in a vertical or horizontal position or at a 45” angle and ignition of the specimen for a set period of time with a flame of a given dimension and temperature. Usually ignition and burning are conducted in a chamber to provide a draft-free burning area, and the time necessary for the flame to extinguish or burn a given distance is measured. Char formation is measured by applying force by weights and tearing the char. T h e distance of char formation is considered a measure of flammability hazard. The following lists some of the inethods using vertical ignition and burning: 1. Method 5902 of Federal Specification CCC-T191b. “Flame Resistance of Cloth--Vertical” (97) 2. AATCC 34-1966 “Fire Resistance of Textile Fabrics” (92) 3. A S T M 626-55T (93) 4. General Motors Match Method 30-27 (Revised 1 1/13/67) (94) Figure 3 shows a schematic of the simple apparatus needed for Method 5902. The fabric speciineii, 2-1/2 in. by 14 in., is placed in a nietal specimen hold so that a 2-in. width is exposed for burning in a tertical position. Ignition in this test is for 12 seconds; the time that the burning of the specimen continues after removal of the burner is recorded as well as glow time after flame extinguishment. T o determine char length, a certain tearing weight is applied depending on the weight per square yard of the cloth prior to treatment. Five specimens from the warp and five from the fill direction of weave are tested. T h e AATCC Method 34-1966 is for all purposes identical to Method CCC-T-191 b, except for modifications in the cabinet to allow for inore draft, and the gas composition is carefully spelled out. Likewise, in the ASTM 626-55T Method, the cabinet is again modified but otherwise the method is the same as the AATCC 34-1966 and Method 5902. T h e National Fire Protection Association has also published a vertical test method which is nearly the sarne as Method 5902 of Federal Specification CCC-T-1916 or the two above A S T M Methods 1706). However, the length of the specimens used are ten inches rather than fourteen inches. The last test in the above table in which the specimen is ignited vertically, the G. M. Match Method 30-27, has recently gained prominence for evaluating flammability of upholstery fabrics for automotive applications. Again the specimens which are 1 in. by 12 in. are preconditioned and then ignited with a wood match (not specified whether large or small) for 15 seconds. T h e specimen is exposed by raising the match if it melts or curls away. A satisfactory flame retarded fabric is one which extinguishes itself within 5 seconds after the match is removed and does not burn past the 6-in. mark. We have found that backcoated nylon fabric that satisfactorily passes the test does so by virtue of the material 50
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Figure 3.
Method 5902flame fesf afparatus
fusing and dripping alvay. If a 1)lend of nylon with rayon is used. then drippiiig is prevented and the test is 1w-y difficult to pass. Duration of afterglow rime is specified but no requirement is stated concerning the burniiig of molten polymer that drips. When evaluating nonwoven materials such as polyestcr, polypropylene, and polyethylene, we have modified the test by placing a piece of absorbent cotton under the burning speciineii and indicating \vhether or not the cotton is ignited by the dripping polymer. I n reality, the match test is probably meaningless for all synthetic fabrics that drip because of poor reproducibility. In fabrics such as nylon-rayon blends, the results are iiiore meaningful because the rayon leaves a char which prevents the polymer from dripping. Likewise it is possible to inodify the test by sewing in glass fiber strands to hold tlic polymer and prevent it from dripping. Another test which is designed to evaluate the burning rate of a fabric in a horizontal position is Method 5906 of Federal Specification CCC-T-19lb (95). I t is stated to be satisfactory for fabric that has not been flameproofed, including pile and napped cloth. In the method, a specimen, 41j2 in. by 12l/2 in., after suitable conditioning and napping, is ignited a t one end with a Bunsen burner while held in a metal frame placed inside a cabinet to prevent drafts. Usually the long dimension is taken parallel to the warp direction of the cloth unless a pattern of the cloth enhances a faster burning rate in onc direction. I n this case, the specimen is taken in thc direction presenting the greatest hazard. After burning 11/2 in., the burning rate over a 10-in. length is determined. An average rate of burning in inches/minutc or seconds of 5 specimens is determined. Another test, AATCC 33-1962 (96),ASTM D1230-61 (LIT), and NFPA No. 702 (107), uses a rather involved apparatus to test the flammability of textiles in a position 45” to the horizontal. The test is specifically applicable to evaluation of the flammability hazard of textile clothing or textiles intended for clothing and by its design tests for dangerous flame spread which ma)- hc
associated with raised or high pile fiber fabrics. In the test, specimens of 2 in. by 6 in. are exposed to a pinpoint flame for 1 second, and time required for the flame to travel 5 in. across the surface of the fabric is measured. Five specimens are normally burned, and the averaged flame spread rate calculated. Based on the burning rate and whether a fabric is raised or nonraised fiber, the fabric is classified into 3 classes: normal flammability, intermediate flammability, and rapid and intense burning. Two methods used to judge the flammability for automotive interior textile trim materials are the Ford Motor Test BN24-1 (98) and Chrysler Motor Horizontal Test LP-463KC-13-01 (99). In the Ford Motor Test, the apparatus shown in Figure 4 is employed. A 6-in. by 6-in. specimen is held vertically and brought in contact with a flame from a hypodermic needle. After igniting for a specified time and then withdrawing the flame, it is noted whether the specimen continues to burn or smolders after removal of the flame and the findings are recorded as required by material standard. I n the Chrysler test procedure, apparatus shown in Figure 5 , the specimen, 4-in. by 4-in., is mounted in a frame and ignited a t one end with a Terrill or Bunsen burner having the gas flow rate carefully regulated to give a luminous flame of a given height. Ignition is for 15 sec and the burning rate deterinincd over a 10-in. distance after the specimen has burned 11/2 in. This appears to be a inodification of Method 5906 of Federal Specification CCC-T-191 b. A rather intriguing test which has been shown to have good sensitivity and range was one developed in the J. P. Stevens Laboratories and is called the ellipse flame test (100). In this test, a schematic of what is shown in
F i p e 5. Chrysler Motor flume test upparatu.r
Figure 6. J. P. Stevens ellipse flume test specimen
Figure 4. Ford Motor flame test apparatus
Figure 6, a piece of fabric which is a quartcr ellipse is held in a vertical position and ignited a t the uppcr edge with a pinpoint flame. With fabric that is very flame resistance, only charring occurs and none of the top edge of the ellipse burns. With fabric having a lesser degree of flame retardancy, the flame travels upward and then extinguishes itself somewhere along the ellipse. (Note that the edge of ellipse is marked off in centiVOL. 6 2
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mctcrs.) T h e test was designed so that only small aniounts of fabric and chemicals are consumed to produce a measurable result (a number) even on specimens of inadequate flame resistance. Referring to Figure 7 , it can be seen that in the usual vertical flame tests described previously, a difficult time is experienced in locating the so-called “breakpoint”-i.e., that point a t which reduction of level of flame retardant add-on causes a very rapid increase i n flammability as measured by char length. This can be time consuming and wasteful in regard to chemicals and fabrics. A new test method which appears extremely proniising for textiles as well as plastics is the so-called “candle test” or oxygen index method (107, 102). A schematic of the test apparatus is shown in Figure 8. This method, developed in the laboratories of General Electric by C. P. Fenimore and F. J. Martin, yields a value known as the limiting ox!.gen index which is defined as the minimum oxygen concentration which permits the entire length of the specimen to burn. This device determines the relative flammability of materials through precise and reproducible measurement of the minimum concentration of oxygen required to just support the burning of a specimen. Oxygen and nitrogen are fed through a highly accurate gas metering unit which consists of flow regulators, calibrated critical flow orifices, Bourdoii test gauges, valves, and gas connections. T h e gases are then fed to the bottom of a pyrex combustion chamber, mixed, and then flow past a specimen. In the case of a tcxtile, the specimen is held in a vertical position in a metal frame of U shape, or it can be supported by a single filament of quartz or hard glass woven loosely through the specirncn. Another method which is receiving increasingly inore attention in testing of synthetic fibers and blends is the semicircular flame test (703-105,8). The schematic of the apparatus for the test is seen in Figure 9. I t involves placing a strip of fabric on a semicircular frame set in a \,ertical position and igniting the fabric a t the bottom of the semicircle. T h e sample burns first in a position similar to the usual vertical flame tests, then after burning progresses to the top of the semicircle
5 IO 15 20 25 WT G A I N - X ADD-ON OF FLAME RETARDANT Figure 7. 52
Typical flame retardant vertical &me test
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Figure 8. Schcmutic diagram of “cnndle test’’ upparutus
similar to a horizontal burning test, and, if burniiig continues long enough, downward as it would in a candle test. I n the test, the angle that the fabric burns through is noted every 1 5 sec and thus one can dctermine : (a) angle at which flame is extinguished (b) time of combustion (c) rate of burning The method has excelleiit rcproducibili ty if conditions are strictly controlled a n d can bc applied to a widc variety of fabrics. Tesoro and coworkers (703) havc found it necessary to modify the tcst when dealing with 1007, polyesters that melt and drip when kurncd giving erroneous results, or when flame retardants were applied to fabrics. The flanie-retarded fabrics didn‘t burn long cnough to get meaningful values for Ixxiiing angle and time. The iniportant modification \vas to use a layer of a nonmelting, untreated fabric such as cotton with the 10070 polyester on the flame-retarded fabric. T h e cotton prevented dripping and also provided fuel to allow the flame-retarded specimens to be evaluated. Conclusion
Synthetic fibers are assuming a greater and greater share of the total textile niarkct. T h e need for effective, diirable flame retardants for synthetic fibers aiicl their blends with natural fibers that do not melt is attaining proper recognition. T h e state of the a r t in flame retarding acrylic fibers is fairly well advanced and cffcctive ways to impart this characteristic arc being employed coiniiiercially today. Little has been published on flame retarding other synthetic fibers such as polyesters, polypropylene, n),lon, other than finishcs. These fibers are rapidly increasing in importance and it is expected that the situation will change and that effectivc techniques \vi11 be employed for obtaining this highly desired characteristic of flame re tardancy. Considerable research effort is being expended by fiber manufacturers, chemical manufacturers, and textile firms to develop flame-retardant fibers for the synthetics. A wealth of technical talcnt as well as new laboratory
Figure 9. Semicircular flame test apparatus
instruments are being brought to bear on the problem of flammability. I t is expected that such effort will bear fruit in the early 70’s and that the growth of synthetic fibers will not be hindered by lack of flame resistance. T h e author thanks the Michigan Chemical Corp. for the opportunity to prepare and present this paper and Mrs. Mary Lombard and Michael Nametz for their assistance in its preparation. References (1) White, W. V., Amer. DyestufReporter, Nov. 4, 49, (1968). (2) Wilkenson, A. W., Brtt. Med. J.,1,37 (1944). (3) Obadiah Wyld, British Patent 551 (1735). (4) Gay-Lussac, J. L., Ann. Chim. 18 (Z), 211 (1821). (5) Kirk Othmer, “Encyclo edia of Chemical Technology,” 2nd ed., Vol.9, Interscience Publishers, New gork, N. Y., 1966, p. 300. (6) Se all W. M., Amer. Dyesfuf Reporter, 58 (6), 22 (1969), reporting on aper by W. kr&e a t Duttweiler Conference on Textile Flammability and &nsumer Safety, Ruschlikm, Switzerland, January, 1969. (7) Schaplowsky, A. F., Proc. Second Annual Meeting, Information Council on Fabric Flammability, New York, N. Y.,Dec. 1968, p. 131. (8) Richards, H. R., Can. Textile J., 80, 41 (1963). (9) Sayers, L. W., Text. Inrt. Znd., 3, 168 (1965). (10) Douglas, D. O., J . SOC.Dyers Cohr., 73, 258 (1957). (11) Vosburgh, W. G., Text. Res. J., 30, 882 (1960). (12) “Man-made Textile Encyclopedia,” J. J. Press, Ed., Interscience, New York, 1959, pp. 143-144. (13) Du Pont Text. Fiber Bull. X-45,November 1955. (14) Coover, Jr., H. W., andDickey, J. B., U.S. Patent 2,763,631 (1956). (15) Wooten, Jr., W. C., and Shields,D. J., U.S. Patent2,879,256 (1959). (16) Hobson, P. H., U.S. Patent 2,949,437 (1960). (17) Mazzolini, C . , and Monaco, S. L., U.S. Patent 3,310,535 (1967). (18) Neth. Appl. 6,517,189 (Monsanto Co.) (1966). (19) Neth. Appl. 6,515,911 (1966). (20) Neth. Appl. 6,517,131 (1966). (21) Neth. Appl. 6,517,132 (1966). (22) Neth. Appl. 6,517,074 (1966).
(23) E. F. Stroh, U.S. Patent 3,379,699 (1968). (24) Chcm. Eng. News, May 1, 1967, p 14. (25) Kovacs, J., andMarve1, C.S., J. PoIym. Sci. Part A-7,5,1279 (1967). (26) Coover, H. W., Jr. and Dickey, J.B., U.S. Patent2,636,027 (1953). (27) Shashona, V. E., US.Patent2,888,434 (1959). (28) Dickey, J.B., and Coover, H. W., U.S. Patent 2,559,854 (1951). (29) King, F. E., Cooke, V.F. G., and Lincoln, J., U.S. Patent 2,999,085 (1961). (30) Dickey, J. B., and Coover, H. W., U.S.Patent2,721,876 (1957). (31) Dickey, J. B., and Coover, H. W., Jr., U S . Patent 2,721,876 (1955). (32) Coover, H. W., Jr., U.S.Patent2,827,475 (1958). (33) Neth. Appl. 6,514,477 (1966). (34) Hirshfeld, J. J., Belg. Patent 631,087 (1963). (35) Krcma, L. Czeck. Patent 100,291 (1961). (36) Dills, W. L.,U.S.2,607,729 (1952). (37) Hirshfeld, J. J., and Burnthall, E. V., U S . Patent 3,047,425 (1962). (38) Hirshfeld, J. J., U.S. Patent 3,383,240 (1968). (39) Perri, J. M., Gcr. Patent 1,221,761 (1966). (40) Tarkington, T. W., and Anderson, N. T., US.Patent 2,949,432 (1960). (41) Palethorpe, G., US. Patent 3,318,978 (1967). (42) Graham, P. R., U.S. Patent2,881,147 (1959). (43) Lowes, F. J., U S . Patent 3,242,124 (1966). (44) Brit. Patent 1,004,889 (1965); also Neth. Appl. 6,401,139 (1964). (45) Blackburn, W. A., and Apperson, C. H., U.S. Patent 3,313,867 (1967). (46) Lowes, F. J., Jr., U S . Patent 3,271,343 (1966). (47) Lowes, F. J., Jr., U S . Patent 3,271,344 (1966). (48) Lowes,F. J., Jr., U S . Patent3,213,052 (1965). Neth.Appl. 6,509,569 (1965). (49) Birum, G., U S . Patent 3,058,941 (1962). (50) Folksdorf, E., Germant Patent 1,036,463 (1958). (51) Rogovin, Z. A., et a[., Knmrchcskic Volokna, 1966 (3), p. 27-30. (52) Robinette, H., Jr., Mod. Text. Mag., 98 (6), 46, 48 (1957). (53) Douglas, D. O., J. Soc. Dyers Colour. 73, 258 (1957). (54) Moretti, L. J., and Nakajima, W. N., U S . Patent 2,922,726 (1960). (55) Conn, R. C., Kosloski, C. L., and Kienlc, R. H., U S . Patent 2,881,152 (1959). (56) Frieser, E., Melliand. Tcxfilber. 40, 436 (1959). (57) Nemes, J. J., U.S. Patent 2,999,847 (1961). (58) Nemes, J. J., et al., U S . Patent 3,308,098 (1967). (59) Rossin, E. H., U.S. Patent 2,795,513 (1957). (60) Polansky, R., and Herbes, W. F., U S Patent 2,854,437 (1958) (61) Krcma, L., and Sedlacek, 2. Czeck. Patent 102,383 (1962). (62) Mosher, H. H., US.Patent 3,017,292 (1962). (63) Burnell, M. R.,U S . Patent 2,953,480 (1960). (64) Iannazzi, J. L., U S . Patent 3,032,440 (1962). (65) Berger, A., Swiss. Patent 364,237 (1962). (66) Hilscher, E., Ger. Patent 1,150,044 (1963). (67) Krcma, L., Textil., 21 (5), 230 (1966). (68) Kubitsky, K., Melh and Texttlber., 95, 66 (1954). (69) Pritchard, J. E., U.S. Patent 2,702,763 (1955). (70) S. A. Walrave, French Patent 1,453,415 (1966). (71) American Fabrics, (82) 90 (1969). (72) Pastuska, G., Gummi, Asbesf, Kunstofc 19 (31, 275 (1966). (73) Hilscher, E., Ger. Patent 1,150,044 (1963). (74) Brit. Patent 1,069,946 (1967). (75) Reinhard, H., and Welzel, G., Brit. Patent 1,054,887 (1967). (76) Gaeth, R., et a/., Ger. Patent 1,169,832 (1964). (77) French Patent 1,394,401 (1965). (78) Brit. Patent 1,126,478 (1968). French Patent 484,485, (1967). (80) Vsiansky, J., et nl., Czeck. Patent 11,352 (1966). (81) Bellus, D., cC al., Czeck. Patent 111,995 (1964). (82) Matsubayaski, K., S e w Cakkaishi, 19 (11, 27 (1963). (83) Tseitlina, L. A., et ai., Khim, Vdokno 1965 (4), pp. 16-19. (84) Johnson, J. H., et al., U.S. Patent 3,210,147 (1965). (85) Orlov, N. F., et al., Izu. Vyssh. Ucheb. Zaued., Tekhnol. Tekst. Prom. 1967 (l), pp. 113-118. (86) Orlov, N. F., USSR Patent 189,515 (1966). (87) Volgina, N. M., et al., Zh. Prtk/. Khtm., 40 ( l ) , 209 (1967). (88) Kiselev, G. A., et a!., tbid., 39 (Z), 388 (1966). (89) Volgina, N. M., et al., USSR Patent 203,832 (1967). (90) Liggett, R. Winston, BUN.South. Res. Znrt., 21, 5 (1968). (91) Method 5902 ofFederal Specification CCC-T-19lb; May 15, 1951. (92) AATCC-34-1966, Amer. Assoc. Text. Chemists Colour. Technical Manual, (93) ASTM Method D626-55T, Tentative Specification 1955 Issued 1941, Revised 1955. (94) General MotorsTest Method 30-27,4thRevision, Nov. 13, 1967. (95) Method 5906 ofFederal Specification CCC-T-19lb; May 15,1951. (96) AATCC-33-1962, Amer. Assoc. Text. Chemists Colour. Technical Manual. (97) ASTM D1230-61-1969 Book of ASTM Standards American Society for Testing and Materials, Phila., Pa., Part 24, pp. 253-258 (1969). (98) Ford Motor Co. Physical Test Method BN24-1, October 30, 1962. (99) Chrysler Corp. Laboratory Procedure LP-463KC-13-01, Nov. 14,1968. (100) Hay, P., Amer. DyestufReporter, 53 (19), 23 (1964). (101) Fenimore, C. P., and Martin, F. J., Mod. Plasf. 44 (3), 141 (1966). (102) Goldblum, K. B., SPE J. 25, 50-52 (1969). (103) Tesoro, G. E., Miller, B., Meiser, C. H., Jr., Text. Res. Znst., Progress Report No. 1, Oct. 14, 1968. (104) Schoen, G., Me/liand Textilbcr. 48, 215 (1967). (105) St. Hilaire, International Contest Paper, AATCC National Convention, New Orleans, 1967. (106) NFPA 701, “Fire Tests-Flame-Resistant Textiles, Films 1968” National Fire Protection Association, 60 Battervmarch St., Boston. Mass. 02112. (107) NFPA 702,“Wearing Ap are1 Flammabiliry 1968.” National Fire Protection Associauon, 60 Batrcrymarch g t . , Boston, Mass. 021 12.
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