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INDUSTRIAL AND ENGINEERING CHEMISTRY LITERATURE CITED
(1) Akin, E. W., Spencer, L. H., and hIacormac, A. R., Am. Dyestvfl Rept., 29, 418, 455 (1940). ( 2 ) Leatherman, M., U. S. Dept. Agr., Circ. 466 (March 1938). (,3,) Little. R. W.. “Flamemoofina Textile Fibers,” New T o t k , Reinhold Pu.blishing Corp., 1947. (4) Natl. Fire Protection Assoc., Boston, Mass., “Reconimendcd
Requirements for Flameproofing of Textiles,” 1941: (5) Katl. Research Council, Div. 9 and 11, Symposium on the Flame-Thrower, Dunbarton Oaks, Washington, D. C. (January 1945). ( 0 ) Satl. Research Council, Project Q.>l.C. 27, Spec. Rept. Subproject 27-R8-11, Columbia University, New York (Junc 12, 1945).
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(7) Ramsbottom, J. E., Brit. Dept. Scientific and Industrial Research, London, Royal Aircraft Establishment (1947). (8) Ramsbottom, J. E., and Snoad, A. W., Brit. Dept. Scientific and Industrial Research, London, seoond rept., Fabrics Co-
ordinating Research Committee (1930).
(9) Sisson, W. A., presented at Office of Quartermaeter General,
conference on Katl. Research Council Project 27 Q.M.C., Washington, D. C. (Dee. 1.5, 1944). (10) State of California, Assembly Bill 726 (passed April 18, I945j. (11) U. S. House of Representatives, H.R. 2496 (introduced RIarch 6 , 1945). RECEIVED January 26, 1950. Contribution from Q.M.C. 27 War Research Project, Department of Chcmioal Engineeiing, Columbia University, Xew York, E.Y .
UATZON OF A M E - R E S I S T A N T FA BRZCS JAMES R‘I. CHURCH, ROBERT W. IJITTLE1,AND SYDKEY COPPIcK2 Columbia University, New Yorlt, N. Y. T h e acceptabiIity of any flameproofed fabric for a given purpose is dependent not only upon its flame resistance, but also upon other textile characteristics which may be altered b y the flameproofing treatment employed. The type of flame-retardant chemical and the conditions used for its incorporation within the fabric not only affect the characteristics of the finished cloth, but also restrict its use for certain applications. The flammability of a fabric is a factor of the combustibility of fiber, type and weight of weave, and effectivenessof any added flame-resistant treatment. The determination of the flame resistance of fabrics has recently been investigated by many laboratories. During the war a n intensive study of this problem was made, the results of which have led to a standardization of flame test methods for a wider acceptance and better agreement between laboratories. Uniform and
consistent results have been obtained by the establishment of rigid procedures for flame tests, w-hich now make i t possible to measure the comparative effectiveness of various flame-resistant treatments and determine the relative value of flame-resistant fabrics for any given purpose. Consideration has been given to not only the extent of flaming produced in the combustion of the fabric but also the rate of burning and the duration of the afterglow, employing the vertical, horizontal, and angle tests. Other methods for testing the acceptability of flame-resistan t fabrics include durability to leaching by tap water, sea water, perspiration, and detergent solutions; deterioration of the fabric or its flame-resistant characteristics in storage or actual use; measurement of fabric strength and porosity; physiological effeets of flame-resistant treatments, such as toxicitj , skin abrasion, and heat loiid.
ARLY during World War I1 it became evident that flameresistant textiles would be required in order to afford effective protection against the rapidly developingfke typeof warfare, with the use of incendiary bombs, flame throwers, and highly combustible fuels in tanks, planes, and ships. As a protective measure, temporary methods were adopted for the treat’ment of textiles wherever possible in an effort to reduce the losses in personnel, equipment, and supplies due to fire. Unfortunately, the best treatments then available Ivere unsuited for use on clot’hing, mainly because they lacked permanence. An intensive search was immediately undertaken in an effort, to discover more suitable flame-retardant agents and practical methods for their ready applicat,ion with existing facilities, in order to perfect a flame-rmistant fabric capable of meeting the stringent military requirements. Such a project was established as part of the war research program in the Department of Cheniical Engineering a t Columbia Universit,y in the fall of 1942, under the sponsorship of the National Research Council Committee on Quartermaster Problems. It had a threefold objective: (1)
iniprovement of existing flame-resistant t.reatments for temporary adoption; (2) investigation of the fundamental principles of flame retardancy, which included the study of t.hc niechanisms by which flame-retardant chemicals function t>odecrease the combustibility of textiles; and (3) search for newer and better flame-retardant agents and iniproved methods t,o provide a more satisfact,orv treatnient of fabrics for military use. Incidental to this, but equally important in many respects, was the development of adequate test methods for a correct evaluation of flame-resistant agents and treatments, as a means of determining their acceptnbility for the uses intended. This not only involved the utilisation of standard test methods already used by the textile industry for other types of fabrics, but in many cases required that a new test method be devised, with rigid standardization of the test procedures, in order to obtain satisfactory quantitative result8 for a reliable evaluation and comparison of flame-resistant treat,ments. The acceptability of a flame-resistant textile cannot be judged by its flame resistance alone, for any flameproofing treatment mill alter the properties of the original textile fiber to some cxt-ent, anti may change its characteristics sufficiently to render the fabric unsuited for the purpose intended. This is particularly true vhere the treatment requires an excessive amount of the flame-
E
1
Present address, Experiment Station, Hercules Powder Co., Wilmington
90, Dei. 9
Present address, Research Department, American Viscose Corp., 1RIar-
cus-Hook. Pa.
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retardant chemical, adding weight and stiffness, and imparting poor wearing quality to the fabric, or where the flame retardant is chemically attached to the textile fiber, thus decreasing its strength characteristics, durability, and usefulness. Ideally, a flame-resistant fabric must resist combustion by fire to the extent of no flaming or glowing, and in normal use retain the original desirable characteristics of the fabric which make it a useful textile. In addition to adequate flame- and glow-resistant qualities, other factors to be considered are permanence of the treatment under actual usage conditions, which include leaching by rain water, perspiration, moisture, tap water, and launderiqg; and effects of the treatment upon the usability of the fabric, such as wearing qualities, deleterious action of the chemicals in the tendering of the fabric with subsequent loss in fabric strength, and discomfort to the user by contact with the flame-retardant chemicals or lack of porosity of the fabric. The ideal flame-resistant treatment should be readily applied directly to the finished fabric or fabricated cloth with standard textile equipment and should retain its effectiveness over long periods under conditions of normal usage. As yet this goal has not been achieved, but many of the newer methods come close to meeting these requirements. The general factors affecting the flame resistance of a fabric are type of textile fiber and its relative ease of combustion, weight and weave of the fabric, and effectiveness of any added flame retardant. The first would include natural fibers such as cotton, wool, flax, silk, and hemp, the regenerative type of cellulose rayons, and the newer synthetic fibers such as cellulose acetate, nylon, vinyls, and acrylics, as well as the inorganic fibers of glass and asbestos. The combustibility of the fiber is fairly well determined by its chemical composition, particularly in the case of the more commonly employed textile fibers which are organic in nature. In the weaving of the fabric, the size, shape, and twist of the yarn, as well as the weave and weight of the fabric, determine its ease of flammability; the looser woven, lighter weight fabrics are generally the more combustible. The third factor, effectiveness of the flame-retardant agent, is not entirely a matter of ability to decrease the combustibility of the fabric but is equally dependent upon an efficient long-term flame resistance with a minimum amount of the retardant. In most instances this is defined in terms of the effectiveness desired for a given type of fabric under the conditions imposed for its use. Therefore the most difficult part in the control of this factor is not essentially the relative efficiency of the fire retardant itself, but the development of an effective treatment that will provide a permanent type of flame resistance. The flame-resistant treatment of fabrics i s an old art, only recently converted to a more scientific basis as a result of fundamental studies of the behavior of flame-retardant chemicals. For many years the common methods employed a great variety of water-soluble compounds, which for the most part were fairly efficient but of short duration. However, these compounds offered the advantage of being easily applied from water solutions. Because of their water-solubility and ewe of removal by leaching, these are to be regarded as temporary flame-resistant treatments, suitable only for interior use where contact with moisture can be avoided. Even under these restricted limitations, the treatment is not considered particularly durable and must be renewed from time to time, owing to a gradual displacement or elimination of the flame retardant from the fabric under normal conditions of use. With the demand for flameproofed fabrics for outdoor use, a more durable type was developed, which consisted of the use of metallic oxides in combination with chlorinated organic compounds. These are applied from suspension in various solvent solutions by a padding technique for impregnation within the fabric. Such a type of treatment provides a fairly efficient nonflaming of the fabric even after long periods of continuous exposure to climatic conditions or excessive leaching in the strong
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detergent solutions employed for commercial laundering. However, the excessive add-on required results in not only increased weight of the fabric but also increased stiffness and harshness which render it unsuitable for wearing apparel. The treatment does serve a useful purpose in the flameproofing of tentage, tarpaulins, and similar outdoor fabrics. More recent improved treatments combine effective flame and glow resistance with durability and usefulness of the fabric. These consist for the most part of either precipitation of the flameproofing agent within the fabric, or attachment of the flame retardant by a chemical action to the fiber in such a way as to make it available for directing the thermal decomposition and preventing combustion of the fabric, a t the same time resisting the effects of climatic or laundering conditions which might otherwise render it ineffective. Flame-resistant fabrics for civilian use are in reality no different than those required for wartime purposes, although military requirements might seem much more stringent. A growing interest by the consuming public in better fabrics, which provide not only superior wearing qualities but also protection to the user in case of fire, is evidenced by the legislative measures that have been adopted or are under conideration at the present time. In the interests of the public, government agencies are now imposing the same restrictions upon the performance characteristics of flameproofed textiles that the military demanded for war purposes, Recent hearings before the Federal Trade Commisvion make it evident that the w e of the term “flameproofed” must imply not only effective resistance of the fabric to both flame and glow, but also a permanence of these characteristics for the life of the fabric under all conditions of use. In light of this public interest and the restrictions to be imposed upon the use of flame-resistant treatments, it is most essential that suitable laboratory test methods be made available for a proper evaluation of flame-resistant fabrics and a classification as to their relative effectiveness. Research on new and improved methods of flame resistance would be of little value if the products developed could not be quantitatively compared in terms of added values of flame and glow resistance, durability of the treatment, and influence upon desirable fabric properties. GENERAL EFFECTIVENESS OF FLAME-RESISTANT FABRICS
The terms “fire resistance” and “flame resistance” imply resistance to destruction by a fire or flame, and are often confused with “fireproofing” and “flameproofing,” which are nonexistent as far as fabrics are concerned. A mabeiial that is flame resistant withstands self-destruction once the igniting source or flame has been removed, but some change in its physical and chemical characteristics due to thermal effects cannot be prevented. The t e r m “fireproofing” and “flameproofing” should be reserved for treatments which render a material totally resistant to any effects by fire or flame, with no appreciable change in its physical or chemical state. This, of course, would be impossible for common fabrics and the terms should therefore be applied only to leas combustible materials. The less resistant materials which are capable of some combustion, but do not burn readily, should be charactefised as “flame-resistant” or “fire-resistant.” This latter term, however, needs further qualification to express degree of resistance. Of equal importance in the flame resistance of fabrics is resistance to afterglow, which, if permitted, may consume the fabric and cause as great damage as the flame itself. It is an inherent tendency of most organic fibers to undergo a nonflaming type of combustion, or glowing action, once the flame has been extinguished. In some instances it may reignite the fabric into a flame. Some types of flame retardants, particularly the metal oxides, are effective in reducing the flaming tendencies of combustible fabrics, but do not prevent the consumption of the fabric by an afterglow, which persists for some time after the source of the flame or heat has been removed. In fact, they actually accelerate
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Table I. Ideal Flameproofing Requirements for Textiles 1. Minimum effective add-on to avoid both excessive increase in weight of fabric and imparting of a poor hand to fabric 2. Means of easy application to fabric, which may permit its use directly with garments or consumer goods 3. Reasonable permanency of treatment toward leaching action of water, salt and soap solutions, and dry-cleaning solvents 4. Freedom from deleterious action upon storage or during oonditions of use which may cause decrease in fabric strength through tendering action 5. No appreciable decrease in permeability of fabric as measured by air and vapor transmission 6. Compatibility of treatment with other treatments used in finishing the fabric 7. Avoidance of physiological action of retardant on skin, in treatment and use of fabric 8. Flameproofing efficiency which prohibits propagation of any flame and any appreciable afterglow; charred fabric still retains considerable of its strength characteristics
the glowing tendency, acting as catalysts for this type of combustion. This afterglow in many applications is a most serious objection, because the intensive heat’s that are produced exceed those of the flame temperatures themselves and can cause a considerable amount of injury and damage to adjacent areas. Therefore, the use of such t e r m as “fire resistance” and “flame resistance” applied to fabrics should also imply prevention of any aftergloTv as well as afterflaming. In other words, a flame-resistant fabric should exhibit no tendency toward further combustion, once the igniting source has been removed or ext,inguished. The effectiveness of any treatment is a matter of the efficiency oC the flame ret,ardant employed and t’he durability of the treatment, which is denoted by a sustained effectiveness under various use conditions which otherwise might destroy the flame resistance of the treated fabric. In view of these requirements, any treatment may therefore be classified in accordance with its effectiveness in t e r m of both the degree of flame and glow resistance and the degree of durability in withstanding any deleterious action t,liat,might decrease the flame or glow resistance. Another classification, in terms of the method of treatment’,does not define the effectiveness of the flameproofing but merely indicates the type of process employed for applying the fire retardant.. The former classification is therefore the most useful. It’is essential to linon. not. only how efficient the treatment is in preventing afterflame and aftergloLv, but also how resistant it is toward any action tending to remove or destroy this resist,ance in normal use. The various treatments may be listed according to whether they are temporary, semidurable, or durable, and the degree of flanieproofness and glowproofness defined. The first group includes all t,hewater-soluble retardants, rrhiuh for the most part are highly efficient but a,re easily destroyed by even the slightest leaching action of moisture. The semidurable class includes treatment’s that show some resistance toward leaching, but readily lose their effectiveness particularly upon laundering. The last class resists the prolonged action of common leaching or laundering agents without appreciable loss in resistant qualities. Consideration of the effectiveness of any flame-resistant treatment should take into account the relative efficiency of the flame retardant in terms of unit prot,eet,ionper unit weight of chemical employed. In fact, the treatment might well be qualified by denoting the degree of flame and glow resistance afforded by a given amount of the flame-retardant chemical. The add-on factor is most important because of the deleterious effect of excessive quantities of the flame-retardant, chemical upon the properties and use of the treated fabric. It is most desirable for commercial applications that rather srnall quantities of highly effective fire
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retardants be employed. The minimum add-on required to prevent appreciable afterflaming, or afterglow, and produce a minimum char length, or char area, as measured by standard flame tests, can be employed to advantage in the comparative evaluation of flame-retardant agents, specifying the relative value in terms of the amount of chemical required. Other factors affecting flameproofing efficiency are concerned with the textile properties of the treated cloth, such as fabric strength, porosity, wear characteristics, appearance, hand, and ease of fabrication into useful articles. Any treatment, however effective and permanent, which seriously decreases or limits the usefulness of the treated fabric, is of questionable value. The ideal flame-resistant treatment should be applied readily to any type of fabric to render it highly resistant to the destructive action of the afterflame and afterglox and should not seriously alter the fabric characteristics for consumer’s use. Such ideal characteristics are useful for judging the acceptance of any flame-resistant agent or treatment and are sumniarized in Table I. METHODS FOR EVALUATING FLAMEPROOF FABRICS
The merit of any flame-resistant treatment is dependent upon its ability to prevent afterflaming and afterglow of the treated fabric, once the igniting source has been removed, and to retain its effectiveness under conditions of climatic exposure, laundering, or storage of the fabric, without seriously affecting desirable fabric properties. Any evaluation of a flame-resistant treatment requires quantitative laboratory test methods for the measurement of its comparative effectiveness. A complete evaluation of the performance characteristics of a flame-resistant treatment is lengthy and time-consuming, and is justified only if it is known that the treatment is fairly effective for the purpose intended and worthy of further consideration. It is often desirable, in t.he case of questionable treatments, first to obtain an initial estimate of the efficiency of the treatment by use of a shorter, more rapid preliminary evaluation. If a favorable result is obtained from preliminary tests, performance characleristics are studied more extensively. The specific tests to be included in either type of evaluat,ion are dependent upon whether the material under examination is a flame-resistant fabric or a flame retardant, and the relative permanency of the treatment. I n the casc of the flame retardants, methods of satisfactory application to a suitable test fabric must be provided in order to assure a proper evaluation of the agent undcr opt.imum conditions. Preliminary Evaluation Procedure. The minimum effective add-on of the flame-ret,ardant compound should first. be estimated. Samples of the test fabric with which the flameproofing agent is to be employed are impregnated Iyith varying amounts of the flame retardant under conditions recommended for a correct t,reatment. Final add-ons within the range of 10 to 30%, represented by four or more specimcns, should be prepared for the flame tests. F ~ a mTESTS.Specimens of the flame-resistant fabric, prepared as above, or samples of the already treated fabric, are first conditioned for 48 hours a t 70” F. and 65% relative humidity before the flame teats are applied. Duplicate determinations are made, noting the time of afterflaming and afterglow as well as char length or char area developed. On t’hebasis of the results of the tests with the specimens of varring add-on, the minimum effedive add-on of the flameproofing agent may be computed. The L6mainderof the evaluation tests should then be made with specimens containing slightly more than the minimum effective add-on. TEXDERING TESTS. In order to determine the estent of any deleterious effect,s of the flame retardant or treatment upon the fabric strength, standard tensile strength measurements are made, employing either the raveled strip or grab tensile strength tests. LEACHINGTESTS.The more permanent treatments are subjected to a few simple leaching experiments. Specimens of the treated fabric are tested for loss in flame resistance and fabric strength after 30-minute immersion in distilled m t e r with stirring; 5-minute immersion in 5% sodium chloride solution, removal of excess, and rinsing for 30 minutes in running tap m t e r ; and one, three, and six launderings in 0.5% G.I. soap (8)
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a t 70" C. (160" F.) for 15 minutes each, followed by two hot tap water rinses between washes. These preliminary tests provide an estimate of the relative efficiency of the initial treatment, the effect of impregnation and deleterious action of the flameproofing agent upon the fabric strength, and the permanency of the treatment to various leaching solutions, end indicate whether further extensive tests should be made for a more complete evaluation of the flameproofing treatment. Complete Evaluation Procedure. With the more effective flame-resistant treatments, a complete evaluation is desirable for a more accurate appraisal of the characteristics of the treated fabric and comparison with other acceptable agents or treatments. These additional tests are designed to show the degree of flame and glow resistance and fabric strengths afforded by the treatment under conditions simulating actual usage of the fabric, such as wearability, durability, laundering effects, and changes occurring during storage. Again, the extensiveness of these tests varies with the permanency of the treatment; leaching experiments with the water-soluble flame retardants are omitted because of their ease of removal. STANDARD FLAME TESTS. More extensive tests, made with varying add-ons of the agent within the effective range indicated by the preliminary tests, provide a more accurate determination of the minimum effective add-on, using the three standard flame tests, the vertical, the horizontal, and the 45" angle tests. In the case of an already treated fabric it is assumed that the add-on of the flame-retardant compound is optimum and only one set of flame tests is possible a t this particular add-on of the treatment. Quintuplicate specimens are prepared and conditioned for 48 hours at 70" F. and 65% relative humidity for each flame test with each add-on. DURABILITY TESTS. Specimens of the treated fabric containing the optimum add-on of the flame retardant, are sudjected to tensile strength measurements by either the grab or strip test method and compared, if possible, with a sample of the untreated fabric to determine the loss in strength after exposure to the following conditions: original untreated and treated fabric "as is"; 2 weeks' storage of treated fabric a t 120" F. and 85% relative humidity; 2 and 4 weeks' storage a t 150' F. dry; five, ten, and fifteen laundering cycles, each consisting of ti 15-minute washing in 0.5% neutral soap, followed by 5-minute hot water rinse, and 30-minute oven drying a t 160 F. Specimens of the exposed treated fabric are subjected to triplicate flame tests to determine the loss, if any, of flame resistance under the conditions of exposure. If the laundering tests show excessive loss in fabric strength or flame resistance of the treated fabric within five launderings, leaching experiments in distilled, tap, and sea water are made, employing 24-hour immersion with stirring in each case, followed by tensile strength measurements and flame tests. Where good durability is exhibited in the extensive neutral laundering tests, a series of launderings in 0.5% standard G.I. soap and 0.5% G.I. soap with added 0.2% soda ash is made, to determine the durability toward fabric strength and resistance under more drastic conditions. SPECIAL TESTS. Other tests for a final acceptance of a flameresistant fabric should include moisture-vapor permeability, resistance to perspiration, and wear resistance, particularly if it is intended for clothing purposes. Before a decision is made to accept a treated fabric for a given purpose, a series af performance tests should be conducted, under normal and accelerated conditions, simulating the exposures the fabric will encounter in use. Tests of this type can best determine the quality and length of service the treated fabric can be expected to render. O
Flammability Tests. The standard flame tests, mentioned above, are briefly described in the following sections, in order better to explain the test conditions under which the experimental data are obtained for comparative evaluation of types of flame-resistant treatments. The flammability tests are designed to determine the relative flame resistance of a fabric, but are not sufficient in themselves for determining the acceptability of the fabric for an intended use. However, the rejection of the treated fabric is justified on the basis of the flame tests alone, if the initially treated fabric shows insufficient flame resistance. I n addition to the three standard flame tests, a flame and glow propagation and a combustion test may be included. Acceptance of test results must necessarily be based upon a careful consideration of the type of fabric and the degree of flame and glow resistance which the fabric is expected to exhibit: whether the most important property is ease of ignition,
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Figure 1. Front View of Flame Test Cabinet rate a t which the fabric will burn if once ignited, or relative propagation of the glow after flaming has ceased. Many flame test methods have been proposed, but few have found wide acceptance, owing to the lack of any quantitative measurement or reproducibility. Essentially the main differences between them have been: nature and intensity of igniting source, shape and size of the fabric specimen, degree and method of conditioning of specimen, position of the specimen in relation to the igniting source, time of exposure to the igniting source, and observations of the flaming, afterglow, and charring of the ignited specimen. All these factors must be rigidly defined in any flame test, if reliable and consistent results are to be expected. The standard flame tests presented below have been subjected to a rigorous standardiaation and found to meet these requirements. Therefore these are to be considered as the most satisfactory methods for determining the relative flame resistance of treated fabrics. VERTICALBUNSEN BURNER FLAME TEST. This is the method most commonly employed by laboratories for the testing of flameresistant fabrics (6). The test cabinet employed is shown in Figures 1and 2 with the vertical specimen in place above the Bunsen burner. Three or more 2 X 12 inch specimens are cut from the sample of treated cloth, with the long dimension in the direction of the warp, and conditioned for 48 hours a t 70" F./6501, relative humidity before testing. In mounting within the cabinet the specimen is held in a suitable clamp at the top and the bottom edge positioned 0.75 inch directly above the top of the burner, with the lower corners held under a slight tension. By use of a quick-acting valve and a butane-air mixture for the burner, a slightly luminous flame 1.5 inches high is applied to the lower edge of the suspended fabric specimen for exactly 12 seconds. A small pilot light, attached to the burner through a swivel joint to allow i t to be moved out of position while adjusting the specimen in place, is recommended for better defining the exact time and extent of ignition. With the extinguishing of the burner flame, observations are made with a stop watch, noting the time in seconds of the afterflaming, and the time of afterglow once the flaming has ceased. The length of char produced by the combined flaming and afterglow is measured in 0.1 inch from the lower edge of the specimen to the uppermost point of the char area. This part of the determination is the most difficult in many cases, where no clear demarcation is evident between the black char area and the original fabric, with a scorched area in between. Attempts have been made to define this area by the use of a tear
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for exactly 12 seconds and the time of afterflaming and afterglow is noted by the aid of a stop watch to 0.1 second. Likewise the char area is measured by a planimeter, following the outline as defined by the mid oint of any scorched area outside the black area of the char. $he requirements cited for satisfactory flame resistance in the horizontal flame test also apply in the case of the 45" angle test.
Figure 2. Side View of Flame Test Cabinet
method. By applying a given weight, varied according to the weight of the fabric, to one of the lower corners by means of a hook, while supporting the other lower corner with a lifting motion a tear is produced through t'he char area into the good portion of the fabric which is strong enough to support the weight. Erroneous results have been due to thermal breakdown of the fabric above the char area without charring, causing the specimen to be t,orn a considerable distance beyond any visible char area. Usually accepting a midpoint in any scorched area as the upper limit of the char length has given reproducible result,s. The accepted criteria for effective flame resistance of a fabric measured by the vertical flame test method are less than 2 seconds' aftesflaming, less than 4 secon.ds' afterglow, and a maximum char length of from 2.5 to 5.5 inches, depending upon the weight of fabric under test, with the higher char lengths allowable for the lighter fabrics. HORIZONTAL ~ ~ I C R O B U R N EFLAME R TEST. This is a modification of the Corps of Engineers "flame-resistance test" ( 5 ) ,made in the cabinet shown in Figures 1 and 2. The 6 X 6 inch fabric specimen is mounted in a square or round metal holder similar to an embroidery hoop. A small microburner with swivel pilot light is provided, and a C . P . butane-air mixture is used for produc,ing a 1.75-inch nonluminous flame. The specimea in the holder is mounted on a support directly above the burner in a horizontal position with t.hc center of the specimen 0.75 inch above the top of the burner. Exactly 12 seconds' exposure to the igniting flame is allowed by use of a quick-acting valve on the gas line to tmheburner and the time of afterflaming and afterglow is noted to 0.1 second. The char area is measured by we of a planiniet,er, using the mean between the outermost part of the scorched and t.he blackened area for defining the char area. For a satisfactory flame-resistant treatment, an afterflaming of less than 2 seconds, an afterglow of less than 4 seconds, and a maximum char area of less than 4.0 square inches, are required. Placing the specimen in a horizontal position gives an exaggerated afterflaming effect due to trapped combustible gases on the underside of the fabric. The reverse is true of the afterglolv tendencies, which are lessened because noncombustible gases above the fabric interfere with the noimal propagation of the glow by air currents flowing upward in the cabinet. THE45" ANGLEMICROBURNER FLAME TESTis a further modification of the British and Canadian flame test method (3). Figure 3 shows the setup of the cabinet, for this test, which is conducted in the same cabinet with the other standard flame test's. The microburner with swivel pilot light is the same as that used in the horizontal test. The 6 X 6 inch conditioned specimens are mounted in the metal frame holder and laced on a rack at a 45" angle with the smooth side upwards. '&he position of the specimen is such t,hat the lower side of the fabric, 1 inch from the lowest edge, is centered 0.75 inch above the burner top. Employing a nonluminous flame 1.75 inches high, the fabric is ignited
For all practical purposes, it is immaterial whether the flame burns in the direction of the warp threads or not, and therefore no consideration is given to the position of the weave of the fabric, in either the horizontal or 45" angle flame tests. The microburner, used in both of these tests, has many advantages over the Bunsen burner, for its nonluminous flame burns much more steadily and is more uniform in size. The temperature of the microburner flame at the point of contact with the fabric is constant at 820" & l o oC., particularly when a uniform source of gas supply, such as butane, is employed. The vertical flame test tends to exaggerate the afterglow, whilc the horizontal flame test exaggerates the afterflaming, hut in the 45" flame tests, the afterflaming and afterglow tendencies are midway between. The 45" angle for contact with the flame more nearly simulates the conditions of contact in actual practicc. Consequently, if only one flame test is to be used, the 45' angle test is to he preferred, especially where afterflaming and afterglow are of equal importance in estimating the flame resistance of a fabric. Regardless of the requirements to he met, considerable experimental data have clearly demonstrated that the 45" test produces much more reliable and reproducible flame test results and allows for a greater differentiation in the comparative evaluation of flameproof efficiencies. FLAMEPROPAGATIOS TESTS. In cases of fabiics that exhibit some degree of flame resistance, or treatments of comparatively low flame-resistant efficiencies, measurement of the relative degree of inflammability is desirable. Such a test also serves to differentiate between hazardous and less combustible fabrics in the enforcement of legislation governing the sale of fabrics that will easily ignite and burn quickly. Several such flame propagation tests have been devised to determine the relative e%e of ignition and the rate of burning. The A.A.T.C.C. Flammability Test ( 4 ) was recently devised to assist in determining the relative flame resistance of nontreated consumers' fabrics.
A special test cabinet is provided with a specimen rack for holding 2 X 7 inch strips of the cloth under examination, some cut len thvise in the direction of the warp, others in the direction of the Ell. These are first conditioned by drying for 15 minutes in an oven at 105" C. and cooled in a desiccator before testing. The specimens are placed in the holder frame, which covers the side edges and holds the material flat. The frame with specimen intact is placed at a 45" angle in the test cabinet. By the use of an automatic lighter and timer, a 1-inch small pointed flame, utilizing a mixture of butane and air as the gas supply, is Impinged upon the lower edge of the fabric for a second ignition and the time in seconds of burning of the fabric from the lower to the top edge is recorded automatically on a stop watch. Just what may be considered a minimum flaming rate for demarcation between acceptable and dangerous fabrics will necassarily depend upon the outcome of extensive correlations by different laboratories, now in progress, Columbia Flame-Rate Propagation Test. The A.A.T.C.C. test is a modification of another flame propagation test devised in these laboratories to distinguish between poorer flame-resistant treatments or evaluation of efficient flame-retardant agents when used in lower add-ons below an effective add-on.
A 2 X 36 inch stiip of the treated fabric, cut in the direction of the warp, is suspended by attachment to a wire within a draftless hood on its edge a t a 30 angle. The strip is marked off in 5-inch sections for measurement of the maximum flame propagation during the burning of the specimen. The fabric is well ignited a t the lower corner by contact with the flame of a Bunsen burner for 5 to 10 seconds, and accurate time of the rate of burning is noted as the flaming portion progresses from one 5-inch section to O
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Figure 3. 4.5' Microburner Flame Test Cabinet Left.
Side view, outside.
Center.
Side view inside.
the next. Disregarding the first and last 5-inch sections, a n average flame-rate propa ation as well as a maximum rate can be readily determined. ! 'he angle of burning can be varied, usin a greater angle for less combustible fabrics, and a smaller angle for more combustible fabrics which allows a greater versatility of this test for fabrics of widely different burning characteristics. Discrepancies in flame test remlts by different laboratories, using the same test method and same test fabric, are usually due to differences either in the composition of gas and the gas pressure employed for the igniting burner or in conditioning of the fabric prior to the flame test. This latter requirement is most important, but the actual temperatures and humidities employed for conditioning the specimens can be varied, as long as they are uniform and a sufficient time of conditioning is used for a comparative evaluation. Different gases of the same B.t.u. content, with the same size of flame for ignition of the test specimens, have been shown to produce variations in char length and char area. Therefore butane gas is to be recommended for standardizing this variable. Fabric Strength Tests. Of primary importance in the evaluation of flame-resistant fabrics is measurement of the effect of the treatment or subsequent effects of use conditions upon the strength characteristics of the cloth. Regardless of the initial efficiency of the flameproofing treatment in preventing afterflaming and afterglow, it would be of little value for any practical application if the fabric strength were so seriously impaired as t o render the fabric unserviceable. Therefore tensile strength and tear resistance measurements are essential in determining the usefulness of the treated fabric initially and after exposure to durability tests. The methods employed for fabric strength determinations are well established and fairly uniformly accepted. Details of test procedures for tensile and tear strength measurements are given in many standard texts (d, 6). TENSILE STRENGTH.In the measurement of breaking strength and elongation of textile fabrics, the A.S.T.M. methods ( 9 ) are employed, using the raveled-strip, cut-strip, and grab methods. In the first two methods 6-inch specimens are cut in the direction of both the warp and the fill. In one case strips 1.25 inches wide are raveled to a width of exactly 1 inch by removing the same number of threads from each side; in the case of nonraveling fabrics or heavily coated fabrics not easily raveled, the width is
Right.
Front view, inside
cub to exactly 1inch. The grab specimens are cut 4 inches wide and 6 inches long in the direction of both the warp and the fill. After conditioning for 48 hours at 70"F. and 65% relative humidity, the specimens are clamped lengthwise in the jaws of the tensile machine and a constant rate of load is applied in pulling the fabric specimen apart, An average of at least five indwidual tests is reported for both the warp and fill breaking strength, and the percentage increase in length of the specimen just before the break is computed in like manner.
TEAR STRENGTH.Two tests are employed for determining the tear resistance of a cloth: the tongue method, and the trapezoid method. In the tongue method, 3 X 8 inch specimens are cut from the fabric in both the warp and fill directions and a %inch longitudinal cut is made in the center of one of the shorter edges, running lengthwise of the specimen after conditioning. The two halves, or tongues, of the cut end are placed in separate jaws of the tensile machine, and a constant rate of load is applied until the fabric tears. The average maximum load required to tear the fabric is reported for the warp and fill tear strength. The trapezoid method employs 3 X 6 inch tonditioned specimens, previously cut from the fabric in both directions, and an isosceles trapezoid marked in the center of the specimen, having an altitude of 3 inches aad bases of 1 and 4 inches, respectively, with the longer edge in the direction of either the warp or the fill. A 0.25-inch cut is made in the fabric, on the center of the 1-inch edge of the trapezoid perpendicular to it. The specimen is clamped in the grab test jaws of the tensile machine along the nonparallel sidw of the trapezoid with the cut halfway between the jaws, 1 inch apart. A constant rate of load is applied to the jaws and the average maximum load required to tear the fabric is reported for both the warp and fill tear strength. There is little correlation between tensile and tear strength, particularly with treated fabrics. Some treatments may impair one without seriously affecting the other. Most of the impairment in fabric strength is due to either chemical action of the treating compound upon the fabric, or a stiffening of the threads of the fabric which decreases the flexibility, causing a shearing action when under stress. Thus treatments that produce a flexible coating or film on the fabric, or tend to lubricate the threads, usually cause an increase in the breaking strength but reduce the tear strength considerably. Which property is to be given the most attention is samewhat dependent upon the use for which the fabric is intended.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Durability Tests. The permanence of a treatment, under the conditions of use! is equally important to the efficiency of the flame retardant, and any flame-resistant fabric, regardless of its initial effectivencss in preventing propagation of a flame or afterglow, is definitely limited in its usefulness if these properties arc easily destroyed or seriously reduced by conditions encountered in use. In some instances, a water-soluble t,reat,ment,which might ordinarily be regarded as uf purely temporary benefit, may prove adequate for indoor use if the leaching action by moisture vnpor or water solutions is avoided. On the ot,her hand, where laundering of the trcated fabric is required, or outdoor exposure with climatic changes is to be encountered, a fairly permanent type of t,reatment, is necessary. It is surprising hoiv much displacement of the flame retardant will occur upon prolonged exposure to moist air, even at relatively low humidities with a water-soluble treatment,, causing a migration of t,he retardant and serious loss of flameproofness in some areas of the fabric. Such effects often occur in the storage of this type of flameproofed fabric, especially 011 the outer folds and edges of the cloth, and where the fabric is entirely exposed by hanging indoors for long periods. Some of the semidurable treatments may be destroyed when the fabric is brought into contact with various solutions where ion exchange with the mineral content of hard water or sea water may occur. Waters containing dissolved calcium, magnesium, or sodium salts, perspiration, or moist sea air seriously affect' the efficiency of this type of treatment. Such a limitation great'ly rcduces the usefulness of this type of flame-resistant fabrics. Therefore the leaching experinleiits included distilled water, hard water, sodium chloride solution, and a "synthetic sea Tvater" containing dissolved calcium, magnesium, and sodium salts. Soaps used in the laundering of fabrics vary according to their alkalinity in their deleterious effects upon the flameretardant efficiency. In the case of the recent synthetic soaps and detergents, which are of a low alkalinity, the efficiency of the more durable treatments is very slightly affected, even nit,h repeated launderings, but with ordinary laundry soaps, especially in commercial practices where soda ash is employed with the soap solution, many of the durable types of flameproofing treat.ments are seriously impaired. The qucstion of how many such leachings or launderings a flame-resistant fabric should be capable of withstanding without serious loss in flame-retardant efficiency can be answered only in terms of the intended use of the fabric. Clothing fabrics would demand a greater durability than most other types of fabrics, especially work clothes, which require rather severe conditions in their laundering. LEACHING TEWSinclude immersion, sprag, and running wntcr tests utilizing distilled and hard natcr. In the static test a 7 X 7 inch fabric specimen, after conditioning for 24 hours at. 70" F. and 6570 relative humidity, attached to a 6 X 6 inch glass stirrer frame, is completely immersed in 4 liters of distilled water contained in a cylindrical glass tank, and st,irred slowly a t 30 to 40 r.p.m. a t room temperature for specified t,ime. After air drying and reconditioning, any change in weight is determincd, and loss in flame resistance in comparison with specimens of the original fabric is noted, by use of the 45" microburner flame test. In the running Ivater leach, a specimen of similar size is immersed in a glass tank and hard water is introduced a t the bottom of the tank a t such a rate that considerable turbulence is produced, to cause a continuous tumbling action of the specimen for 24 hours a t slightly above the hard water temperature of 50" to GO" F. Any change in weight, %me resistance, and fabric strengt,h following the t'est is determined a,s in the static water test. Exposure to large quantities of hard water may result in ion exchange, causing the flame retardant to lose its effectiveness, depending upon the hardness of the city water used. The spray leach test is part of the accelerated weathering test (11) conducted by use of t.he Weatherometer machine, Model X-lA, manufactured by the National Carbon Company. Here 12.5 x 11 inch specimens of thc treated fabric are given a conical spray of distilled water for 10-minute periods each 2 hours, following exposure to the artificial sunlight of a carbon arc for the re-
Vol. 42, No. 3
mainder of the cycle for a total exposure of from 200 to GOO hours. The exposed samples are examined for change in weight,, flameproofing efficiency, and fabric strength.
LAUNDERING TESTS.These are made wit,h 0.5% soap solutions varying in alkalinity by employing (1) a neutral synthetic detergent such as Igepon-T (General Dyestuffs Corporation, New Yorlr, S.Y,), (2) ordinary yellow laundry soap, suc,h as G.I. issue (8), and (3) laundry soap with 0.2% added soda ash. The temperatures of the washing solutions are usually kept at 160" E'. and the specimen is rotated in the soap solution with a tumbling action for a definite period of time. Several rinses usually follow, which include hot water, cold m t e r , and dilute acetic acid for removal of any soap residues. The time and exact temperature of these rinses vary somewhat according to the laundering method (1, 2, 6 ) . Several machines have been suggested for t'he laundering test, but only two are used to any great extent. The Atlas Launder-Ometer, perhaps the most common for laboratory use, ut'iliees glass jars containing a number of glass marbles or steel balls with a specified amoout of the soap solution for washing single small specimens of fabric. The jars are clumped to a rotor driven at a slow speed for an end-over-end tumbling of the jars immersed in a constant temperature water bath contained in a horizontal tank. The other machine is a small table-type washing machine with a reversing agitator motor drive or a small reversing wash wheel of the cylindrical type. These v.31 accommodate large specimens and more nearly approximate t,he conditions of a home or commercial laundry. Following the laundering cycle, the larger specimen, or several of the smaller specimens, are air-dried and reconditioned, and changes in weight, flame resistance, and fabric strength are determined by standard test methods.
SPECIAL EXPOSURE TESTS. For a more complete evaluation of tBhedurability of a more permanent type of flame-resistant treatment, tests are employed to indicate the resistance of the flame retardant upon exposure to sea water, perspiration, and climat,ic conditions, such as those produced by accelerated weathering of the Keatherometer or by actual indoor and outdoor storage. The resistance of a durable flame-retardant treatment to the action of sea water might most commonly be associated with the use of marine fabrics, but actually climatic conditions along the coastal areas include sea water mists and salty air, and these are similar in their action to sea water itself. In fact, the test is closely related to the more common leaching tests, for it involves the possible ion exchange of the sodium, mitgnesium, and calcium salts of sea Tater, as wit.h hard tap water. The test is carried out by immersion of 7 X 7 inch conditioned specimens in 250 ml. of a synthetic sea water prepared according t o the formula of Lyman and Fleming (IO) contained in a pint Mason jar. Several jars are attached i o a slowly revolving rotator and tumbled for 1 and 2 hours at 70" F. After the excess of the sea water is wrung out, the specimens are air dried, reconditioned 24 hours a t 70" F. and 557, relative humidity, and examined for changes in weight, flame and glow resistance, and fabric strength. Resistance to perspiration is not necessarily limited to flameresistant clot,hing, but is universal for d l fabrics, because it is also concerned with a possible ion exchange for decreasing the flame and glow resistance of the fabric. This test is slightly more severe than the sea water test, because some tendering is caused by the acid constituents of perspiration, in addition to loss in flame resistance, An accelerated test was devised in these laboratories to approximate as closely as possible the conditions encountered by a fabric in contact with profuse sweating. The apparatus consists of an enclosed cabinet' where a 7 X 7 inch specimen of the fabric under test is attached to a revolving frame located within the test cabinet. The specimen is sprayed intermittently each hour with a mist of 30 ml. of a synthetic acid perspiration solution, prepared according to a government formula (6) containing sodium chloride, lactic acid, and disodium phosphate. Evaporation occurs between sprayings while a body
March 1950
*
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
temperature of 98" F. is maintained within the cabinet. After 8 hours' exposure, the specimen is removed from the cabinet, and reconditioned for 24 hours a t 70" F. and 65% relative humidity before being examined for changes in weight, flame and glow resistance, and tensile strength. The accelerated weathering tests are conducted in the Weatherometer unit, manufactured by the National Carbon Company, accordin to standard procedures of the U. S. Army (6) w%ere 12.5 X 11 inch specimens are intermittently exposed to a water spray and artificial sunlight of a carbon arc, as described above under the leaching tests, for long periods of 200 to 600 hours. The better flame-resistant fabrics, which show considerable resistance to the accelerated weathering tests, are given actual outdoor exposure tests. Here larger 42 X 30 inch specimens are exposed to the weather a t a 45' angle facing south for periods up to one year, mostly during the six months from April to November. Also important is the exposure of flame-resistant fabrics to indoor storage conditions, which should include both dry and humid storage. A conditioning cabinet with variable temperature and humidity controls is employed for the storage tests. I n the case of dry storage an accelerated temperature of 150" F. is used with exposure for several weeks. For the humid storage tests a temperature of 120"F. and 85% relative humidity are employed for 2 weeks or more. The reconditioned specimens, after exposure under the respective storage conditions, are examined for loss in flame and glow resistance and fabric strength.
425
Table 11. Comparative Evaluation of Water-Soluble Fire Retardants (8.5-ounce O.D.herringbone twill treated with effective add-ons) Test
AFa
AGa
Result CA*
T
S
d
T
BORAX-BORIC ACID, 12% ADD-ON,LABORATORY TRBIATMENT 45' flame test treated fabric 0 10 1.6 113 ... 0 25 2.5 Vertical flame'test, treated fabric T a p water leach immersion (Complete ~oss'df'fire rekisiance) Sea water leach,'immersion soap Laundering 0.5% G.I. (Complete loss of fire resistance resistance! Dry storag;, 150° F./4 weeks 0 12 2.3 118 Humid storage, 120° F./85% R.H./2 weeks 0 110 2.4 126 ,, Normal storage, 70° F./65% R.H./2 months 3 200 4.2 103 ,
... . ..
DIAMMONIUM PHOSPHATE, 11% ADD-ON, LABORATORY TREATMENT 45' flame test treated fabric 0 0 3.7 118 ~~Vertical flame'test, treated fabric 0 0 3.7 T a p water leach, immersion (Complete loss'di loss of fire resistance Sea water leach, immersion (Complete resistance Laundering, 0.5% G.I. soap (Complete loss of fire resistance Dry storage 150° F./4 weeks 0 0 3.2 82 Humid stordge, 120° F./85% R.H./2 weeks 0 0 4.2 105 Normal storage, 70° F./65% R.H./2 months 0 9 3.5 114 ...
...
1..... .
BORAX-BORIC ACID-DIAMMONIUM P H O S P H A T(7~:3:1), 13% ADD-ON 45' flame test treated fabric Vertical flame'test treated fabric Tap water leach ihmersion Sea water leach 'immersion' Laundering 0.5% G.I. soap Dry storagd 150' F./4 weeks Humid stordge 120' F./85% R.H./2 weeks Normal storag;, 70° F./65 R.H./2 months
4 1.8 120 ... 7 3.1 (Complete ~oss'difire risitance) (Complete loss of fire resistance (Complete loss of fire resistance] 33 0 7.1 113 ... 60 0 (Complete) 124 0 11 2.0 116
0 0
.. .. ..
BORAX-DIAMMONIUM PHOSPHATE ( l : l ) , 11% ADD-ON 45' flame test treated fabric 1 0 1.6 123 Vertical flame'test. t , r e a t d fabric 0 2 3.3 T a o water leaah. Complete loss'&' fire reiib'tance) Complete loss of fire resistance) (Complete loss of fire resistancej 0 0 1.8 106 6 2 2.4 96 ... Normal storage, 70° I 0 9 2.3 128
. ..
... Physiological Tests. Although these are more closely related to flame-resistant fabrics intended AMMONIUM SULFAMATB, 15% ADD-ON for clothing purposes, toxicological tests are also important for all types of treated fabrics that 45' flame test, treated fabric 0 398 4.7 126 ~ , . Vertical flame test treated fabric 0 366 3.4 may come in contact with the skin during treatTap water leach, ihmersion (Complete ~ o s s ' dfire i resltance) Sea water leach, immersion omplete loss of fire resistance ment, storage, or use. When used for clothing, Laundering, 0.5% G.I. soap {gomplete loss of fire resistance] flame-resistant fabrics must not produce a heat Dry storage, 150' F./4 weeks 0 9 2.4 53 ... Humid storage 120° F./85% R.H./2 weeks 0 47 2.0 105 load upon the wearer due to lack of porosity or Normal storag;, 70° F./65% R.H./2 months 0 158 3.2 86 .. ,, ., cause any harsh irritating action due to rubbing AMMONIUM SULFAMATE-DIAMMONIUM PHOSPHATE (COMMERCIAL PRODUCT), 15% ADD-ON against the skin. 45' flame test treated fabric 1 0 3.2 123 ... The toxicity tests include an examination of Vertical flame'test, treated fabric 1 0 ... 3.1 Tap water leach, immersion (Complete loss of fire reil'tance) both the basic chemicals used in the flameSea water leach, immersion (Complete loss of fire resistance Laundering 0.5% G.I. soap (Complete loss of fire resistance] retardant treatment and the flame-resistant cloth Dry storag; 150' F./4 weeks 2 0 3.6 54 ... itself. These are standard toxicological tests Humid stordge, 120° F./85% R.H./2 weeks 1 0 2.8 93 Normal storage, 70° F./65% R.H./2 months 0 0 2 . 4 128 .., with test animals and actual skin patch tests (9). DIAMMONIUM PHOSPHATE-AMMONIUM SULFATE (COMMERCIAL PRODUCT), 15% ADD-ON Before heat load experiments are made, the relative moisture permeability of the flame-resistant 45' flame test treated fabric 0 2 2.5 125 Vertical flame'test treated fabric 0 3 i:6 fabric should be determined in order to ascertain Tap water leach ihmersion (Complete loss'di fire resisltanoe) Sea water leach 'immersion (Complete loss of fire resistance) whether the porosity of the fabric has been Laundering 0.5% G.I. soap (Complete loss of fire resistance) seriously lessened by application of the flameDry storagd 150' F . / 4 weeks 36 4 3.7 112 Humid stor&e 120° F./85% R.H./2 weeks 27 3 4.6 121 retardant compound. With the impregnated Normal storag;, 70° F./65% R.H./2 months 0 5 2.1 127 types of treatment, when largc add-ons of heavy AMMONIUM SULFATE-BORIC ACID(COMMERCIAL PRODUCT), 12% ADD-ON metal oxides and resinous materials are employed, 45' flame test treated fabric 0 0 3.6 128 ... the interstices of the fabric are likely to become Vertical flame'test treated fabric 0 3.7 T a p water leach ihmersion Complete loss'df' fire rebGance saturated with the flame-retarding compound. Sea water leach 'immersion . Complete loss of fire resistance] Laundering 0.5% G.I. soap This results in a fabric of low moisture permeaComplete loss of fire resistance) Dry storage) 150' F./4 weeks 164 26 5.7 86 bility, which will produce excessive heat loads Humid stordge, 120° F./85% R.H./2 weeks 126 12 4.8 103 ... 70" F./65% R.H./2 months Normal storage, 0 5 2 . 6 120 when garments made from the treated cloth are ' Afterflaming, seconds. Warp strength, 1-inch raveled strip. worn. Moisture-vapor permeability measureAfterglow, seconds. a Char length, inches. ments of treated fabrics are best made by the Char area, sq. inches. method of Fourt and Harris ( 7 ) ,which relates this to the intrinsic resistance of the treated fabric. This is expressed in terms of equivalent centimeity (65% relative humidity) a t 70 F. for 24 hours, with the ters of still air as determined by comparison of the fabric before and drying agent in contact with one side of the assembled layers of after treatment with the flameproofing compound, to show the resistanceto the passage of moisture vapor caused by the treatment. cloth under examination and a uniform current of the moist air passing steadily over the outer exposed specimen of cloth. Weighing the entire assembly accurately on an analytical balance specimens of the untreated and treated fabric are sealed in a t 80-minute intervals, and noting the rate Of pickup Of moisture multilayers Over a cylindrical flat-bottomed shallow glass dish, over a period of 2 to 3 hours, will furnish sufficient data for comcontaining a known weight of a drying agent such as Drierit@. puting the intrinsic resistance of the treated cloth from a formula These are exposed to an atmosphere of high but constant humid-
...
...
,.. ... ...
... ...
'
O
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 42, No. 3
acceptance of various types of flame-rcsistant fabrics. They are arranged according to the (Effective add-on twith 8 5-ounce herringbone twill) durability of the treatment and cover all classes Flame Test Resultsn of flame-retardant agents: water-soluble salts, Fabric Specimen S F b AGC CAd o r C L * TSJ' urea-phosphate type treatments, metallic oxideUREA-DIANMONIIJN PHOSPHATE, 12% ADD-OX LABORATORY T R C I T Y E N T , 17;' ].:./IS h I I K chlorinated compound combinations, and im0 0 2.4 78 Initial treatment (46') pregnated water-insoluble pigments. 0 1 Initial treatment (vertical) 2.0 78 Temporary Treatments of Commercial ReT a p water leach, continuous, 24 hours 0 1 2.1 70 0 0 Sea water leach, static, 2 hours 3.7 68 tardants. The first of these are the water-soluble 1 2 3.5 53 Laundering, 3 cycles 0.5% G.I. soap Normal storage 70° IF./65% K.H./2 nionths 2 0 3.1 72 retardants composed of salts of boric, phosHumid storage,'l2O0 F./85% R.H./2 weeks 0 0 2.8 80 phoric, sulfuric, and sulfaniic acids, usually em0 0 3.2 66 Dry storage, 150' F./1 month 1 1 Outdoor exposure, 1 month 3.4 63 ployed in the form of their ammonium salts. ~ R E A - D I A M . ? f O X I U A I P I I O S P I I I T B , 16% . k D D - O S . COXMERCIAL THEATAIEXT, 150' F./30 h f I N . Mixtures of t.ivo or more of these salts are 0 0 2.0 92 Initial treatment (45") commonly blended together along with a wetting 0 0 Initial treatment (vertical) 3.4 92 0 0 2.2 88 T a p water leach, continuous, 24 hours agent, which provides a suitable compound that 0 1 Sea water leach, static, 2 hours 2.8 72 is applied to the fabric from a solution of the Neutral soap laundering 6 1 3.2 83 6 cvcles. Iszeaon T mixture in water in varying concentrations. The 3 cicles; 0:5% G.I. soan 1 2 3.9 61 Alkaline soap laundering, 1 cycle, O.>% G . I . soap, fabric to be treated is immersed in the flame0.2% soda ash 36 2 (Complete) 56 retardant solution containing a given concentra24% A D D - o K GvAsInIKE-DIAAIrUoNrv\I I'HOSPIIATE, tion of the compound, the cloth is completely 0 1 2.1 88 Initial treatment (45') saturated by iepcated wringing out and soak0 1 2.4 88 Initial treatment (vertical) 0 1 2.1 78 T a p water leach, continuous, 24 hours ing, and finally a sufficient amount of the flame 0 0 2.3 76 Sea water leach, static, 2 hours retardant is left, indicated by the wet pickup, 0 2 2.8 52 Laundering, 6 cycles, 0.5% G.I. soap 0 1 2.5 78 Normal storage 70° F./65% EE.II.,2 months for an efficient flame retardancy, which is usually 2.6 0 70 2 Ilumid storage, 120' F./85% K . H . , 2 weeks 0 3.2 G2 2 about 15% on a dry weight add-on bahis. In Dry storage 150' F./1 month 0 1 2.6 81 Outdoor exdosure, 1 month most of these evaluations desized 8.5-ounce 0.d. CYAKAhIIDI D E R I ~ A T I ~ E - D I A ~ P~HI0:6O P BSAIT~E ~ , 18% ~ ADD-ON, CO>lSlERCIALTREATXENT herringbone twill cloth m-as employed as the test 1.50' F./30 NIN. fabric. Initial treatment (45') .. ... ... 112 Initial treatment (vertical) 0 2 3.9 112 The test results shown in Table I1 indicate that T a p water leach, continuous 0 1 2.8 108 Sea water leach, static, 1 hour 0 2 3.2 IO6 the water-soluble retardants are, for the most Launderings part, efficient flame retardants but are not capa0 2 3.3 103 5 cycles 0.5% Igepon-'r 3 4 6.3 81 10 cycds, 0.5% Igepon-T ble of withstanding the slightest leaching without Char area, sq, iilches. a 4 5 O microburner flame test uiiiese a complete loss of their flame-resistant efficiencies. e Char length, inches. otherwise specified. Only a slight loss in tensile strength results from / \Varp tensile strength, 1-inch raveled strip Afterflaming, seconds. Afterglow, seconds. the initial treatment, but serious losses occur in the case of sulfamate and phosphate salts upon prolonged storage at excessive normal temperatures, due to the tendering action of the liberated acid. which expresses it as the reciprocal of the moisture pcimeability These are therefore to be recommended only as temporary of an equivalent length of still air through which water vapor treatments, restricted to indoor use, with a warning that the would diffuse a t the same rate under the same conditions of treatment should be renewed after each exposure l o perspiration, tem erature, pressure, and concentration gradient. excessive moisture, or water immersion, by employing a solution T i e actual heat load experiments are conducted with a selected group of individuals wearing garments made from the of the fire retardant as a final rinse in the laundering. flame-resistant fabric while performing some standard work. Semidurable Treatments. A11 the results reported in Tablc 111 During the course of this exercise, physiological data such as pulse are from tests with fabrics treated by the nitrogen-phosphate type rate, rectal temperature, sweat loss, and possibly skin temperaof flame retardant. Some of these are commercially treated tures are taken. Similar data are obtained with the same group of individuals wearing what may be considered normal nonheatfabrics, while others were prepared in these laboratories. A producing clothing, in order to compute any heat load imposed vater solution of the mixture of nitrogen and phosphate comby the treated garments. pounds was applied to the fabric by repeated immersion for a COMPARATIVE EVALUATIONS OF FLAME-RESISTANT AGENTS definite wet pickup, the treatment was set by a heat cure at eleA N D TREATMENTS vated temperatures, and the water-soluble salts remaining were washed out to produce a fairly durable type of treatment. The The procedures described above were developed after cxteiisive main differences between these treatments arc the composition of evaluation studies of many proposed test methods and have been the treating solution and the conditions of the heat cum. For fairly well accepted by most laboratories as standard for the the most part the flame resistance of the treatment is durable evaluation of the flame-resistant qualities of various treated under the usual conditions of use but is soniewhat impaired by fabrics. Not only have these methods been of considerable value contact with alkaline or salt solutions, because of the susceptiin the evaluation of flame-resistant treatments, as part of the bility of the nitrogen-phosphate combination to ion exchange. experimental developments leading to new and improved methTherefore, where the laundering conditions can be controlled by ods of treatment, but they have been particularly adaptable for use of neutral soaps, or contact with csccssive perspiration or sea evaluation and comparison of already available commercial flamcwater can be avoided, this type of treatment providos a fairly retardant agents and treated fabrics. Ovcr fifty different types efficient and durable flame resistance. of flame retardants and commercially treated fabrics were exOne major disadvantage of this type of treatment, howevrr, is amined by these laboratories as a service to the Quartermaster the serious loss in fabric strength, compared with that of the Corps during the war. Some were of little or no practicalvalue, original untreated fabric. Excessive launderings, particularly w, disclosed by the preliminary evaluation and therefore no when sour rinses are employed, causc further loss in fabric exhaustive tests were conducted. Several of the better retardant strength. agents and treatments, as disclosed by the results of complete Durable Types of Treatments. The last group consists of thc evaluations, are presented here to demonstrate the usefulness and impregnated or precipitated type of treatment, utilizing watervalue of these test procedures and methods for a comparison and
Table 111.
Evaluation of Nitrogen-Phosphate Treated Fabrics
INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1950
a
insoluble compounds padded within the fabric from an emulsion or suspension. Others are precipitated under controlled conditions from soluble components by use of a double bath technique, depositing a water-insoluble compound within the interstices of the fabric. The more durable flame resistance obtained by these methods is somewhat offset by a considerable increase in the weight, and a decrease in porosity, of the treated fabric caused by the higher add-ons of the flame retardant required for effective flame resistance. Table IV shows that in most instances an appreciable afterglow occurs in the flame tests. This is accelerated by the presence of the metallic oxides and detracts from the otherwise fairly efficient flame-resistant qualities of the treatment. In many of these treatments containing heavy metallic oxides improved glow resistance can be provided by the inclusion of a glow retardant in the combination. However, even with the addition of an insoluble glow retardant, effective glow resistance is difficult to achieve and is of questionable durability, as it is easily removed upon laundering by a mechanical action.
427
Table IV. Evaluation of Pigment-Resin Type Treated Fabrics (Effective add-ons with 8.5-ounce herringbone twill) Flame Test Resulta Fabric Specimen AFb AGO C A d o r C L e T S I OXIDE-CHLORINATED WAX-ZINC BORATE,33% ADD-ON,LABORATORY TREATXENT EVULSION Initial treatment (45O) 0 InitIil treatment (Gertical) 0 0 Tap water leach, continuous, 24 hours 0 Sea water leach, static, 2 hours 0 Laundering 6 cycles, 0.5% G.I.soap soda ash 0 Normal stoiage, 70° F./65% R.H./2 months 0 Humid storage, 120° F./85% R . H . / l month 0 Dry storage 150’ F./1 month 0 Weatheromtker, 180 hours 0 Outdoor exposure, 1 month Moisture vapor resistance, % increase ANTIMOSY
+
ANTIMONYOXIDE-CHLORINATED WAX-ZINC BORATE,35% ADD-ON, COMMERCIAL TREATMENT
Initial treatment (45’) Initial treatment (vertical) Tap water leach, continuous, 24 hours Sea water leach, static, 8 hours Laundering, 6 cycles,, 0.5% G.I.soap Various storage conditions Moisture vapor resistance, % increase
E?.IULSION
+ soda ash
0 0
0 0 0
28 2.9 132 63 4.6 132 56 3.2 135 58 3.3 136 67 5.6 130 (Fire resistance unaffected) 192
OXIDW-POLYVINYL CHLORIDE-ZINC BORATE,40% ADD-OK,SE?.iICO\IMERCIAL TREATMENT FROM ORGAXIC SOLVENT SUMENSION Initial treatment (45”) 0 0 3.6 143 2 4.75 143 Initial treatment (vertical) 0 Tap water leach, continuous, 24 hours 0 5 3.2 148 Sea water leach, static, 2 hours 0 10 2.9 146 Laundering, 6 cycles, 0.5% G,I. soap soda ash 0 4 2 5 148 Storage and weathering, varying conditions (Fire resistance unaffected) 140 240 Moisture vapor resistance, % increase ANTIVONY
,+
CONCLUSIONS
There is still a need for a better type of treatment, by which fabrics of all sorts can be made highly flame- and glow-resistant, and possessing greater durability than the best of those now available. Minimum add-on of the fire retardant for an effective flame resistance is essential in order to minimize any effects in the fabric characteristics which might result from the treatment. Even the best of the present treatments are lacking in efficiency, particularly from the standpoint of glow resistance, or in fabric strength because of deleterious action upon the fabric, or high add-ons which increase the weight of the fabric and decrease the flexibility and moisture permeability. In order to achieve an ideal type of flame resistance to meet these requirements continued basic research on the fundamentals of flame retardancy must be continued in order better to understand the true function of the flameretardant chemicals and their behavior in contact with various fibers under the influence of heat, Only by the use of fundamental data obtained from researches of this type can a superior process be devised which will fully utilize the complete benefits of an efficient fire retardant, permanently k e d within the fibers of a fabric uniformly to produce a permanent and highly effective flame-resistant fabric. ACKNOWLEDGMENT
ZINC
OXIDE, 29% ADD-ON, COhl>lERCIALTREATXEKT, ORGANICSOLVENT DOUBLEBATH 0 2 3.9 123 Initial treatment (45’) 0 3 3.5 123 Initial treatment (vertical) 0 2 3 . 8 124 Tao water leach, continuous, 24 hours S e i water leach, static, 2 hours 0 1 3.4 128 Laundering 3 cycles 0.5% G.I. soap 0 84 2.6 130 6 cycles: 0.5% G.I. soap 1 126 2.9 132 Storage and weathering, varying conditions (Fire resistance unaffected) 126 740 Moisture vapor resistance, % increase CHLORIDE-BORAX-.4NTI?dONY
STANNICTUSGSTATE, RESIN COATED,33% ADD-OS LABORATORY TREATMENT, AQUEOUS DOUBLEBATR 0 122 Initial treatment (45’) 0 122 Initial treatment (vertical) 0 126 Tap water leach, continuous, 48 hours 0 125 Sea water leach, static, 2 hours 0 127 Laundering, 6 cycles, 0.5% G.I. soap (Fire 126 Storage and weather, varying conditions Moisture-vapor resistance, % increase ANTI~ONY-TITANIU~I-ZINC OXIDES, 16% ADD-ON.SEXICOMMYERCIAL, AQUEOUSDOUBLE BAT@ 0 200 3.8 201 Initial treatment 1 200 3.9 198 Tap water leach, continuous, 24 hours 1 200 4.2 193 Spa water leach. static. 2 hours Laundering. 5 cycles, 0.5% Igepon-T 0 200 4.4 188 1 200 5.7 190 10 cycles 0 . 5 8 Igepon-T soda ash (Fire resistance destroyed) 196 1 cycle, 0.5% soap
6.1.
+
BROMINATED POLYPHOSPHATE ESTER,25% ADD-ON,SEMICOXXERCIAL, SOLVENT^ 0 0 6.7 210 Initial treatment 0 0 6 . 5 206 Tap water leach, continuous 0 0 6.8 198 Laundering, 5 cycles, 0.57’ Igepon T 0 0 6.2 192 10 cycles, 0.5% Igepon-$ Char length, inches. a 45O microburner flame test f Warp tensile strength, 1 inch unless otherwise specified. raveled strip test. b Afterflaming, seconds. g Sateen twill cloth used in place Afterglow, seconds. . of 8.5 ounce herringbone twill. d Char area, sq. inches.
The authors wish to express their appreciation to the many members of the technical staff associated in the work of N.R.C. Project Q.M.C. 27 during the war, from which these results have been taken. They especially thank those contributing to the evaluation tests: Frances s. Lang, John R. Adams, Jr., Roy Becker, Kenneth G. Englar, Lawrence Soos, Jr., and Richard Steinschneider, Jr. LITERATURE CITED
(1)Am. Assoc. Textile Chemists and Colorists, “Standard A.A.T. C.C. Test Methods, 1948 Year Book,” Oficial Method C-1-42 (No.3). (2) Am. SOC. Testing Materials, “A.S.T.M. Standards on Textile Materials,” 1948. (3)British Standards Institute, Specification 476 (1932). (4) Buck, G. S., Jr., Am. Dyestuf. Reptr., 35 (May 6, 1946); 38, 78 (Jan. 24,1949). ( 5 ) Corps of Engineers, Tentative Specification E.B.P. 674 (June 1944).
(6) Federal Standard Stock Catalog, Sec. IV, Part 5 , Textiles,
General Specifications, Test Methods, Supplement, CCC-T191a (October 1945). (7) National Research Council, Committee on Aviation Medicine, Division of Medical Science, Rept. 243 (Jan. 7, 1944). (8) Quartermaster Corps, J.G.Q.D. Specification 1008A (1945). (9) Schwartr, L.,and Peck, 5. M., U. S,Pub. Health Service, Pub. Health Rept., 59,No.17,546-57 (1944);Reprint 2252. (10) Sverdrup, Johnson, and Fleming, “The Oceans,” N e w York, Prentice-Hall, 1943. (11) U. S. Army, SpeciJication 100-48,See. IV (1945). RECEIVEDOctober 25, 1949. Contribution from N.R.C. Project Q.M.C. 27, Department of Chemical Engineering, Columbia University, New York
N. Y.
