>at.ed Fabrics in
constructi.on Industry FIGURE1. MECHANICAL SCRUBBING EQUIPMENT FOR TESTING COATED FABRIC
N
ATURAL fibers employed in weaving include flax, cotton, wool, and silk; among synthetic fibers in commercial use are rayon, paper yarn, and various metallic products. Protection of the woven fabrics by impregnation or coating treatments imparts many useful properties, greatly adding to their value and service. These treatments are of different types, varying as regards chemical composition and method of manufacture. Of the various coatings, those of pyroxylin and of rubber find a number of applications in the building industry.
Application of Coatings The first patents for the protection of cloth with pyroxylin coatings were issued almost a century ago. The industry was not fully established, however, until about 1900. The average annual production in the United States over the past decade corresponds to approximately 38,000,000yards. In this type of coating the protective film is built up by the application of a plurality of coats. In contrast with drying oil coatings, such as are used in the manufacture of oilcloth, which depend upon oxidation and polymerization for their “set-up,” pyroxylin coating compositions contain a nondrying oil and depend upon solvent evaporation. The preparatory treatment of fabric commences with such operations as diastasing, napping, dyeing, etc. The cotton fabrics commonly used may be of the plain weave type such as sheetings, or twill weaves such as drills, sateens, or moleskins. The weight range of fabrics commonly treated varies from 2 to 20 ounces per square yard. Pyroxylin dispersed in a suitable solvent mixture, such as ethyl acetate and ethyl alcohol, is blended in suitable proportions with pigment and a softener such as castor oil. This composition is then applied to the fabric with the aid of a “doctor knife” or suitable coating device. I n applying a plurality of coats, the solvent from each is evaporated before application of succeeding coats. Solvent is recovered in many instances by such means as direct condensation or adsorption by activated carbon. At the desired point in the coating operation, embossing may be applied, followed by various treatments involving use of contrasting colors and decorative effects (4). The production of rubberized fabrics commences with the preparation of the cloth as already described. Rubber is blended with pigment, accelerator, and antioxidant, and applied to the fabric by calendering. In certain cases, however, 1400
DORMAN McBURNEY
Fabrikoid Division, E. I. du Pont de Nemours & Company, Inc., Newburgh, N. Y.
solvent is added and the composition is applied to cloth with a doctor knife as has been described. Rubber-coated fabrics may be embossed and finished with suitable top coating compositions and subjected to curing treatments as the intended use may require.
Testing the Finished Product Evaluation of the finished product depends upon the intended use. For years the custom requirements of this industry have necessitated a number of specialized tests (1). Fabric specifications involve the usual tests such as weight, thread count, tensile, tearing, and bursting strength, which are likewise used in the evaluation of coated fabrics. In addition t o the fabric tests, the following are also employed in ~
The application of a rubber or a pyroxylin composition to fabric imparts special properties particularly desirable for many uses in the building industry. Among important coated fabrics used in building are window shade material, shower curtains, upholstery material, resilient carpet underlay (or floor covering), motion picture screen material, rubberized fabric ventilating tube, and removable weather stripping. For certain requirements DuPrene coatings are also being developed. A number of special tests are described for the evaluation of coated fabrics which make possible the use of definite specifications.
evaluating the finished product: evaluation of light fastness, anchorage of coating, combining strength of double texture material, resistance to cracking and abrasion. Various forms of flexing and folding equipment are used also to measure resistance to cracking. These tests are sufficiently well known to require no special comment. Developed more specifically by the coated fabrics industry is the mechanical ‘‘scrub test.” This test simulates the commonly practiced method of testing coated fabric by grasping adjacent areas firmly by the two hands and vigorously scrubbing the material back and forth until the first break in the coating is developed. The mechanical scrubbing equipment developed in this country (Figure 1) is now employed in coated-fabric plants in Canada, England, France, and Australia. Another important requirement of material which is to stand outdoor exposure is resistance to the exudation or “spewing” of oil. Laboratory tests are made either by exposing the sample for a stated period of time in an oven or in a copper block (Figure 2) which is kept a t the desired temperature in an oil bath. The end point is defined by the temperature a t which oil first appears on the surface. The higher the exudation temperature, the more suitable is the coated fabric for outdoor service in summer or excessively hot climates. With the exudation test, the companion “cold-crack” test should be mentioned. This test defines the temperature a t which the coating will crack when sharply folded. To eliminate the personal element, mechanical equipment housed in a specially designed Frigidaire cabinet has been developed (Figure 3). In this test the material after chilling for a specified time a t a given temperature is subjected to the fall of a specified weight operating within the refrigerating chamber. The ideal combination is to have in the same material a high exudation and a low cold-crack temperature. Accelerated aging tests are made by means of storage a t elevated temperature and, in the case of rubber-coated fabrics, in the oxygen bomb. For a number of applications special testing equipment has been built for accelerated evaluation simulating actual conditions of service. For example, window shade material is tested by being subjected to continuous raising and lowering on standard shade rollers under a fixed
FIGURE 2. APPARATUS FOR DETERMINNG EXUD.4TION OF O I L BY
BLOCK METHOD
tension. Outdoor exposure tests are also conducted on various types of coated material in Kew York, Delaware, and Florida. Several types of coated fabric have been selected for special comment which are of particular interest to the building construction industry.
Pyroxylin-Coated Window Shade Material Window shade cloth came into use many centuries ago.
It was introduced in this country a t an early date but was not popular until the advent of the self-winding spring roller during the last seventy-five years. The first popular shades mere made of paper. They had wooden slats glued horizontally a t varying levels provided with a hook to support them a t the desired height. After the introduction of the spring roller the stress and strain was too great for the paper material, and coated fabric came into general use. There are three general types of coatings commonly employed for shade material. The cheapest have a pigmented
FIGURE 3. SPECIALLY DESIGNED FRIGIDAIRE EQUIPMEXT FOR DETERMINING COLD-CRACK TEMPERATURE OF PYROXYLIN-COATED FABRIC 1401
1NDUSTRIAL AND ENGINEERING CHEMISTRY
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starch base and become badly distorted when wet. The second class is made by treating a fabric with a suitable sizing such as glue which in turn is coated with a linseed oil paint as a top coat. Both of these types of coating are applied to various fabrics. Xeither possesses the resistance to moisture or the washability of the third class of material which is made by treatment with a pigmented pyroxylin coating. This type of material is not damaged by wind and rain and can be cleaned readily with the aid of soap and water. This development was accomplished through a systematic study of various types of fabric and fabric constructions, combined with the development of special coating compositions for this particular kind of service. Considerable study has been given recently by illuminating engineers to lighting the interiors of homes and officebuildings with daylight. This problem has been studied in considerable detail by Randall and Martin ( 6 ) , H i g b i e (S), a n d others. The problem is not only one of light transrnission but also of obtaining u n i f o r m diffusion. Translucent types of pyroxylincoated fabrics have a r e l a t i v e l y high l i g h t transmission factor. This with the diffusion realized results in a balanced combination v e r y desirable for interior i l l u m i n a tion. That pyroxylin-coated window shade material meets a definite req u i r e m e n t of the building industry is e v i d e n t f r o m its widespread uqe in federal b u i 1d i n g s , in hundreds o f
F I G U R E 4. \ ABOVE: UPHOLSTERY FLEXING EQUIPMENT. BELOW: POSITION OF CUSHION AFTER DEPRESSING
VOL. 27, NO. 12
schools and colleges, and in numerous office buildings throughout the country.
Shower Curtains In many new constructions as well as in remodeling, the problem of shower bath equipment arises. Even with builtin compartments the choice of a shower curtain involves consideration. Two types of coated fabrics designed for this use may be described as water-repellent and water-proof. The former consists of a suitable impregnation treatment which imparts to the fibers the water-shedding properties characteristic of the well-known “duck’s back.” In this case, however, the interstices of the fabric are not closed and water can be forced through under pressure. The other type of treatment consists in the application of a full coating in which the interstices are actually filled. This treatment results in a m-ater-proof product. While the type of installation or personal preference may occasion some choice between these two types of shower curtains, the advantages of either over untreated fabric are obvious.
Upholstery Material In the field of upholstery the requirements for coated fabric are varied. Both rubber and pyroxylin coatings are employed. Mention may also be made of double-texture upholstery material in which two fabrics are combined with rubber and the finished surface is coated with a pyroxylin composition. Pyroxylin-coated material is available in the full range of colors and can be embossed in a wide variety of grains. Recently developed pyroxylin-coated fabrics have shown excellent resistance to outdoor service conditions, with no sign of exudation throughout the most severe summer heat. d feature of either pyroxylin- or rubber-coated upholstery material is their water-proofness and cleanability with soap and m-ater. In testing upholstery material, use is made of equipment which simulates the actual service to which the upholstery is 2ubjected on bellom-type theater seats and on modern springtype cushions. One of these machines is shown in Figure 4. Certain types of coated-fabric upholstery material have undergone over a million flexings on this type of testing equipment without showing perceptible breaks in the coating.
JIotion Picture Screen Material Coated fabric finds an interesting application in its use for motion picture screens, With the development of the motion picture industry there has been a constant search for screens having improved reflection characteristics. In the early days fabrics coated with aluminum compositions were commonly used. They are characterized by a high degree of reflection within a narrow angle and by a sharp fade-out on either side (a). This means that with an aluminum screen the picture appears very bright to individuals sitting in the center of the theater and much fainter to those sitting on the sides. To overcome this defect, various means have been employed; one consists in embossing the surface of the screen. Later developments resulted in the more general use of material having a white surface because of the superior optical effects which could be realized. With this type of product a much greater uniformity of the reflection of light is developed throughout the entire arc of the theater, which is an extremely important matter in a wide auditorium. For sound pictures, which require a porous screen, various types of materials have been employed. Closely woven wire-mesh screens have good optical properties but are inferior with respect to acoustic properties, Loosely woven silk fabrics are satisfactory
DECEMBER, 1935
INDUSTRIAL AND ENGINEERING CHEMISTRY
from a n acoustic angle but are poor optically. A screen combining to best advantage the desired optical and acoustic properties has been realized in a fully coated fabric, perforated to permit passage of sound. I n making this type of screen, it is possible to build up a surface with coating compositions formulated particularly to realize optimum reflecting conditions. Reflection characteristics of an aluminumcoated screen, an ordinary white screen, and a specially developed matte finish screen material are shown in Figure 5 . The comparatively wide and uniform range of reflection in the case of the last mentioned material will be observed. An important accomplishment in this field has been the development of a fire-resistant motion picture screen material. This product when subjected to a blowtorch for several minutes will not support a flame when the torch is removed and has been passed by the Kational Board of Fire Underwriters.
Rubberized-Fabric Ventilating Tube A flexible rubberized fabric made into tubular form is used for conducting air in ventilating tunnels and shafts. This also offers a suitable means of conveying conditioned air to various parts of a building where temporary metal lines are impractical or have not been previously installed. B s compared with metallic ducts this material is relatively light, one man being able to carry 200 feet with ease. This product has been employed for a number of years in underground mining operations, sinking of shafts, and the building of tunnels.
1403 j
I
I
\
4
ANGLE
Jurfucr A/um/num B r ~ y h tWh/te--........ Spec/c?/Matte-
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OF C (Degrees)
FIGURE 5 . REFLECTION CHARACTERISTICS OF MOVINGPICTURE SCREENMATERIAL
DuPrene-Coated Fabrics With the development of the new synthetic rubber, DuPrene, study has been given to its use as a coating for fabric. The resulting products are flexible, have all the properties of a rubber-coated fabric, and in addition have the ability to withstand the action of petroleum products such as gasoline, kerosene, lubricating oils, greases, etc., as well as many chemicals. It is unusually resistant to aging under ordinary conditions. For this reason it is finding many uses where a flexible, gas-impervious, oil-resistant fabric is desirable, It may also be dry-cleaned with gasoline. With this material there are no doubt many new uses which will occur to engineers in the building construction industry.
Weather- Stripping
Literature Cited
A new rubber-coated product for weather-stripping doorand windows has been developed recently. It consists of a
(1) Benger, E. B., and Nickowitz, N. M., AutomotiveInd., 49, 1262-6. 1306-8 (1923). (2) Cameron, J. R., “Motion Picture Projection,” 4th ed., pp. 197204. Cameron Pub. Co., 1928. (3) Higbie, H. H., and Younplove, Trans. Illum. Eng. SOC.(K.Y.), 19, 235-68 (1924); Higbie, Ibid., 22, 302-25 (1927); 24, 253300 (1929). (4) Nollau, E. H., 5. A . E . Journal, 22, 2, 219-21 (1927). (5) Randall, W. C., and Martin, A. J., Trans. Illurn. Eng. SOC. (N. Y . ) ,25, 262-81 (1930); 26, 275-91 (1931); 27, 278-88 (1932).
sponge rubber strip to one side of which a n adhesive is applied. This adhesive is protected with a liner similar to that used on a tire patch. When applying, the protective liner is pulled off and the strip is pressed against the surface of the door or window frame where protection is desired and a tight joint free from air leakage is obtained. If it should be desirable to remove this stripping a t a later date, it can be pulled off as easily as a piece of adhesive tape. Kormally no appreciable deposit remains but, if under unusual conditions a slight amount of the adhesive is left behind, it can be removed readily with a cloth dampened with gasoline.
RECEIVED May 1. 1935. Presented
as part of the Symposium on Materials of Construction in the Building Industry before the Division of Industrial and Engineering Chemistry at the 89th Meeting of the American Chemical Society, New York, N. Y . , April 22 t o 26, 1935.
Karaya G u m Correction Our attention has been called to an omission in the literature cited a t the end of our paper on “Karaya Gum” which was published on page 1215 of the October, 1935, number of INDUSTRIAL AND ENGINEERING CHEMISTRY.We regret that the paper by Jerome Alexander on “Zone of Maximum Colloidality. Its Relation to Viscosity in Hydrophile Colloids, Especially Karaya Gum and Gelatin,” which appeared on pages 434 to 440 of the Journal of the American Chemical Society for 1921, was not included. The latter paper called attention to the fact that heating the dry gum decreases the viscosity of its solutions; that heating the solutions decreases their viscosity; that the viscosity is due to hydration and swelling; that as the dispersed phase becomes less viscous by swelling, the colloid as a whole becomes more viscous; and that the degree of fineness t o which the sample is ground affects the viscosity of solutions [the larger particles having less rind (exterior) surface per unit weight will give suspensions of lower viscosity].
In thAsconnection, we failed to mention in our paper that all uf our samples were thoroughly mixed and commercially ground to pass a ZOO-mesh sieve. Therefore our work and our method
of evaluating commercially ground samples are valid. However, unground gum samples should be ground t o 200 mesh if they are to be compared with a 200-mesh standard because the suspensions of the larger particles reach their maximum viscosity much later. A mass of data on certain factors, such as the presence of electrolytes, heating, ash constituents, etc., has been collected in this laboratory. When the results are presented for publication, the work of Jerome Alexander will receive more detailed attention. W. E. THRUN H. V. FULLER
VALPARAISO, IND. November 8, 1935
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