ELASTOMERS
-
HARRY L. FISHER, U. S . Industrial Chemicals, Inc., Baltimore, M d .
S
YXTHETIC rubbers continue to hold their own even though natural rubber is selling for approximately 2 cents a pound less than GR-S, the synthetic rubber of greatest production. The use of over 300,000 tons annually of GR-S and other synrhetic rubbers is not entirely because of government rulings because a t least 170,000 tons iwre purchased last year by hmerican manufacturers on a strictly volunt,ary basis. American manufacturers buy synthetic rubbers on specifications that, enable them to buy the type best suited for their rcquircments and with the knowledge that tvhat they buy will be up to specification (41). Efforts are being made by the plantation people to produce natural rubber of a more uniform quality and with special characteristics. One new continuous process uses ail endless belt that passes through a bath of coagulant and then through latex; the coagulated film is removcd, mashed, dried, and rolled into a cylindrical form or folded flat (60). The rubber thus produced is superior to regular grades in uniformity, cleanliness, and purity. The biggest n m possible use of natural rubber and probably synthetic rubber too, since the advznt of latex foam, is in road building (25, 41). Rubber added to bitumen raises the softening temperature, lowers the penetration, reduces plastic flow practically to zero, and raises the resistance to compact (8). In practice, either the whole mass is mixed with rubber or a seal coat is used. I t is estimated that from one third of a ton to 8 tons of rubber to a mile of highway !vi11 be used. Test roads in Java and Holland (87) and more recently in .4kron, Ohio, show good wear and reduced slipperiness. More roads are being built or are under construction in this country. Silicone rubbers keep their properties over an unusually wide range of temperatures. This range has now been extended; a new Silastic stays flexible from -180" to +600° F., while the tensile strength is over 600 pounds per square inch (16). Butadiene-styrene and similar copolymers pripared in the German Buna S-3 system are stiff but can be heat-softened. Tread stocks prepared from them give about 50% bet,ter wear than GR-S, and are superior in resistance to cut growth (19). COLD RUBBERS
Regular GR-S is prepared by the emulsion copolymerization It has been kno1v-n for several years that GR-Y prepared a t lower temperatures showed superior properties over the regular, but the production time required n-as 2 to 5 days as compared with 15 hours. The development of reagents for more rapid polymerization recipes has reduced the time a t low temperatures until it is now possible to complete the polymerization in the short time of 2 to 5 hours a t -4" F. ( 2 ) . Ordinarily recipes are used that give about 70% conversion in 15 hours a t 41 O F., although by the use of a freezingpoint depressant such as methanol the reaction has been carried out a t -35" F. The low temperature GR-S or cold rubber shows about 30% higher tensile strength than regular GR-S, and greater resistance to abrasion, tear, and flex cracking. When compounded with channel black in a tread recipe it gives better mileage than natural rubber, and with the new furnace blacks i t gives about 30% better wear (29, 39, 80, 84, 86). The relatively poor processing characteristics of cold rubber can in general be overcome by proper mixing in a Banbury (21) and especially by the use of a very fine furnace black (11). Low temperature GR-S does not crystallize when cooled to -70" C., as observed uf butadiene and styrene a t 122" F.
by x-ray diffraction methods. However, polybutadiene formcd a t 20' C. or below shows crystallization effects when cooled unstretched to -70" C. (6). GR-S LATEX
The size of particles in the latex of polymcrs and copolymers is governed almost wholly by the stabilizing capacity of the medium. They grow in size as the copolymer forms in the disperse phase (66). Particle size has only slight influence on the quality of the elastomer, but the fluidity of latices can be increased by increasing the particle size (9). By the use of an agent-for example, carbon dioxide-that prevents the formation of impervious surface skins on drying latex and with the correct humidity, i t is possible to prepare by casting and setting in an oven a t 50" C. films from various types of latices that are smooth and of uniform thickness, superior appearance, higher tensile strength, and greater extensibility than ordinary films (48). Staple fibers of rayon and cotton need no adhesive treatment for satisfactory bonding to rubber, and cord produced from staple rayon picks up more solids from latex than continuous-filament rayon. Adhesion is a function of pickup of solids (33). A review of latex thread and its industrial applications has been published (42). PHYSICAL PROPERTIES
I n a study of frictional properties of tread-type compounds on ice, the coefficients of dynamic and static friction mere measured (20). The coefficients mere very sensitive to the type of carbon black and softening agent; the softer the vulcanizate, the higher the coefficients, and the higher the coefficicnts the better the performance of the compound on ice. The type of polymer was found to have the greatest influence on the Coefficients. Vulcanizates from alcohol-coagulated GR-S, polyisoprene, blends of GR-S and natural rubber and of GR-S and ncoprenc, all showed higher coefficients than regular GR-S. Nitrile rubbers, isoprenestyrene copolymer, Butyl, sodium-polymerized GR-S, and butadiene-chlorostyrene copolymer have low coefficients of dynamic friction. Butyl had a greater tendency to pick up ice and snow than any other type. h property of reclaimed rubber which does not show as much difference from crude rubber as indicated by the stress-strain curves is the abrasion resistance (86). I n the two compounds studied, the ratio of energy of resilience is 682 to 85, whereas the laboratory abrasion resistance (Williams abrader) is 513 to 248. Hencky's stress-strain relation for large deformations of an elastic solid has been applied to the specific cases of pure tension, compression, bending, shear, and torsion (18). I n experiments performed at 35' C. over a 1000-hour period and for a range of elongations up to 430%, GR-S exhibited greater creep than natural rubber (32). The specific heat of unvulcanized natural rubber is constant for elongations up to 300% (62). Vulcanized samples are of two types. One type shoxvvs a linear, reversible, small increase (approximately 0.002 cal. per gram per 1 per 100% elongation) up to 350% elongation. In the other group, of which neoprene is a member, the specific heat is constant up to 150 to 200% elongation, then suddenly increases in a nonlinear, nonreversible manner (approximately 0.020 cal. per gram per 1" per 100% elongation). X-ray analysis shows that partial and increasing crystallization occurs in the region of increased specific heat.
2115
2116
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 NEOPRENE
An excellent review has been published (IS) of the processing of neoprene, including mastication, mill mixing, Banbury mixing, controlling uncured stiffness with types, extrusion, calendering, molding and curing, and storage stability of general-purpose neoprene, and retention of tack and uncured flexibility. Neoprene vulcanized with 0.125 to 0.50 part of antimony trisulfide gives products having high resilience and low heat build-up (83). There is no abnormal tendency of the mix to scorch. Suitable compounded neoprene vulcanizates are satisfactory for use on bare copper wire, with elimination of tinned wire for many applications (51). An antioxidant is particularly important-for example, disalicylal ethylenediamine. White GR-M (neoprene) vulcanizates discolor differently in direct outdoor sunlight from what would be predicted from results obtained with standard lightaging devices (73). Stocks most stable to sunlight are obtained by using high proportions of the rutile crystalline form of titanium dioxide as the white pigment. I t had been shown that neoprene vulcanizates possess greater damping and higher thermal conductivity than natural rubber: now it has been shown that variations in frequency and load affect natural rubber and neoprene vulcanizates in a like manner, and that the dynamic properties of neoprene vulcanizates, particularly resilience, are not so greatly affected by the addition of incxased proportions of carbon black as those of natural rubber (14). Creep of neoprene vulcanizates has been studied as a function of the degree of vulcanization, preconditioning in shear a t olevated temperatures, and composition (43). Curves showing the effect of these three variables give the percentage of relative creep against log time up to 3.75 years. The degree of swelling of neoprene-carbon black vulcanizates in a petroleum oil depend? on both the percentage and the type carbon black (15). Chemical, galvanic, and electrolytic corrosion of load cable sheathpan be prevented by the use of a neoprene (70 mils thick) and neoprene-coated fabric covering of the sheath, vulcanized i n place (64). Polyfluoroprene is amorphous, and, contrary to polychloroprene (neoprene), high tensile properties are obtained only with reinforcing fillers (54). Copolymerization of fluoroprenc with other 1,3-dienes and monovinyl compounds proceeds smoothly and yields elzstomers that are superior, when vulcanized, to polyfluoroprene in processing and tensile properties. Copolymers containing 30 to 40% acrylopitrile give highly oil-resistant vulcanizates and tire-tread compounds having tensile strcngths of 4500 to 5000 pounds per square inch.
Vol. 41, No. 10
giT.e high impact resistance m d can bc: machined and polished (78). COMPOUKDIKG
Tensile strengths up to 1200 pounds per square inch and good abrasion properties are obtained with GR-S without the use of carbon black by a double vulcanization. One hundred parts of GR-S are heated with 0.5 part of sulfur until the sulfur is all chemically combined and then additional sulfur and compounding ingredients are added and the mixture cured (4). Nickel N,N1dibutyldithiocarbamate (NBC) is an inhibitor of dynamic a b mospheric exposure cracking of GR-S and of both static and dynamic cracking of GR-S vulcanizates ( 3 ) . It is somewhat eflective in natural rubber but may have an adverse effect on aging. 2,6-Di-tert-butyl-4-methylphenol (Ional and Deenax) has fairly good nonstaining antioxidant properties and has an appreciable effect in retarding ozone cracking. Although the finer furnace blacks, particularly those made from oil, are difficult to process owing to a high rate of scorch, they impart properties to vulcanized natural rubber a t least, equal to those produced by the channel blacks (60). The story of a slightly hydrated silica (Hi Sil) which about equals the physical properties of the gas-phase produced silica (white carbon black) has been told interestingly together with the stories of fine particle size calcium carbonate (Calcene) and calcium silicate (Silene) (10). In a study of the behavior of several inorganic pigments of fine particle size in natural rubber, neoprene, GR-8, Hycar, and Butyl, it was found that tensile strengths varied but stiffness, hardness, and resistance to tearing increased (19). In synthetic elastomers, clays are outstanding in reinforcement in comparison with other nonblack fillers (34). The usual reinforcing agents when added to latex give poor or no reinforcing effect to the resulting compound unless the compound, after being dried, is ground mechanically. Lignin, however, as already reported, gives good reinforcing properties by simple addition to latex. Lignin that has been oxidized by passing air through its solution and incorporated into natura! rubber or GR-S latex before coagulation gives a rubber that when vulcanized gives excellent properties, even approaching the resistance to abrasion given only by carbon black (24, 63). In GR-S it also acts as a good nonstaining antioxidant. I t has a small effect in darkening rubber, but the color is easily masked by white pigment for producing colored goods. Peat is stated to be an advantageous as well as a cheap filler for GR-S. It is a good binding agent in the production of GR-S building board, and ammoniated peat is a good blowing agent, for the production of sponge rubber (23).
NEW R U B B E R S
BuLadiene-vinylpyridine vulcanizates have higher stress moduli and tensile strengths and lower extensibility than GR-S but the temperature rises through hysteresis are in general higher (97). Polyisoprene can be prepared in solvents by the catalytic action of tert-butyl peroxide (61). The product is free from gel and impurities, and makes a clear solution up to 50% concentration. Copolymers of butadiene and methyl isopropenyl ketone are superior to GR-S in tensile strength a t room temperature and 100 C., and in resistance to hot-flex cut growth and swelling by oil and iso-octane (36). Elastomeric itr-alkyl polyamides have been prepared (91). CHEMICAL DERIVATIVES AND B L E N D S
Hydrorubber, of molecular weights of 100,000 to 200,000, suitable for use as insulating material, is produced by hydrogenating natural rubber by using a nickel-kieselguhr catalyst (67). An insoluble inert ebonitelike product is obtained from natural rubber, dry hydrogen chloride, and formaldehyde (37). Vulcanized blends of elastomers and high styrene resins, formulated with fillers, reinforcing agcnts, and colored pigments,
ADHESIVES
In an article containing an interesting discussion of natural rubber as an adhesive, it is stated that rubber is capable of forming bonds by virtue of dry tack, Also good condensation polymers are described that arc good adhesives (62). Adhesive cements, prepared by mixing chlorinated rubber and a butadiene copolymer, especially a nitrile rubber, in suitable solvents, are stated to be superior for bonding natural and synthetic rubbers to wood, metal, porcelain, paper, leather, or glass ( 3 1 ) . THEORETICAL STUDIES
It is difficult to discuss briefly the procedure and meaning 01 theoretical work. However, it seems desirable that attention be called to interesting and important articles, and it is hoped tha; some good will result from brief statements and the references to them. Uncured natural rubber when subjected t o pile bonibardnienc undergoes a slight curing action, whereas polyisobutylenc is appreciably degraded ($9). S o measurable unsaturation is produced in polyisobutylene and only a little in natural rubhw
October 1949
INDUSTRIAL AND ENGINEERING CHEMISTRY
Butyl is permanently degraded. Thioglycolic acid adds exothermically to butadiene polymers and copolymers to give apparent double-bond saturation values of 38 to 47% (79). It is suggested that the double bonds so saturated are predominantly those present in the polymer chains as vinyl sidechains. When mixtures of purified natural rubber and sulfur are vulcanized in vacuo, the olefinic unsaturation is diminished but the hydrogen to carbon ratio remains 8 to 5 up to a t least 9% combined sulfur. When the rubber-sulfur mixtures are vulcanized in evacuated tubes containing a hydrogen sulfide absorbent, the sate of combination of sulfur with the rubber is abnormally low. Rubber-sulfur mixtures vulcanized in the presence of hydrogen sulfide show normal progressive changes in physical properties, with no indication that the efficiency of sulfur in cross linking is influenced by hydrogen sulfide. If the vulcanization of rubber is analogous to the reaction of simple olefins with sulfur, with the formation of thiols (mercaptans) as intermediates, the transformation of the thiol groups into disulfide and polysulfide linkages is highly probable, particularly when zinc oxide, a zinc soap, or an accelerator containing imino-N is also present ( 7 ) . The temperature rise was small inside vulcanizing samples of the same composition when measured a t 130" and 148" C.; hence, the evolution of hydrogen sulfide is not due to the temperature rise inside a sample (59). Laboratory cylinders of compositions of natural and synthetic rubbers were vulcanized under high pressures up to 100,000 pounds per square inch. The results are indicative of differences in the vulcanization reactions. Resilience was increased considerably in both natural rubber and GR-S, especially in tread stocks; dynamic modulus was higher in GR-S and lower in natural rubber tread and pure gum stocks (89). GR-S is vulcanized by the Peachey process (sulfur dioxide and nydrogen sulfide), and now it has been shown that Butyl and several different nitrile rubbers are also vulcanized but none as well as natural rubber (6). Neoprene did not respond. A precise precipitation fraction of GR-5 (X55) yielded nine fractions, each of about 150 grams, with number-average molecular weights of 4000 to 1,650,000 (92). Only fractions 1 to 6 were vulcanizable. The tensile values at break increased linearly with increasing molecular weight reaching a limiting value around 400,000; the first five fractions had higher values than that of the unfractionated GR-S. For equivalent 300% modulus values as the molecular weight increased, the Goodrich hysteresis and Durometer hardness values decreased and the percentage of Schepper rebound, tensile and elongation at break, quality index, and flex rating values tended to increase. Considerably more data are given. Azo esters of the composition (CH&C(p-CaHdOCON.SCOOCzH& can induce the vulcanization of natural rubber without heat (90). Mathematical analyses of stress and strain have been made and the thermodynamic differential equations integrated in terms of suitable deformation values. Adiabatic compressibility coefficients (both first and second order) were measured on nine different cured polymers under pressures up to 5000 pounds per square inch and the linear isothermal compressibility calculated. Evidence that stress is proportional to the absolute temperature is provided by reported thermoelasticity measurements in torsion (55). I n experiments on natural and German Buna rubbers, it was found that the plasticity is a function of the mean chain length; in all cases the higher the K value, the less plastic is the polymer, and the greater the degradation (the longer the time of heating), the more plastic is the polymer f26). The fundamental character of the flow phenomenon can be explained on the basis of the theory of highly elastic materials with their microfluid state of aggregation, which explains also why the mechanical properties of rubber depend so greatly on t h e temperature (70). The tem-
2117
perature dependence of the rate of flow is accounted for on the basis of the simple Eyring formula, a value of 8.1 kg.-cal. per mole being obtained for the energy of activation involved in the flow process (74). Symmetry of the shape, as well as of intermolecular forces, in the molecular units, size of substituents, and regularity of the polymer chain, all have an essential influence on the rate and ease of crystallization (7g). The second-order transition temperatures ( T m ) for fourteen commercially available nitrile rubbers with 18 to 50% of acrylonitrile have been determined refractonietrically and found to be somewhat lower than the corresponding brittle temperatures (2'6). The data show a linear relation between T m and acrylonitrile content (88). The product of sound velocity and density is approximately the same for rubber and for water, in which the measurements were made; the average value obtained was 1479 * 3 meters per second (46). A close parallel was found in the mechanical and dielectric properties of Buna polymers, the results of mechanical damping and electric loss factor being represented by similarly shaped curves on the one hand and of elasticity modulus and dielectric constant on the other (68). METHODS OF TESTING
The oxidative deterioration of rubber a t elevated tcmperatures, 100' and 130' C., is the simultaneous result of cross linking, which hardens the rubber, and scission of the molecules, which causes it t o become tacky. The experimental methods employed involve measurements of oxygen absorption and relaxation of stress, and these may be of value in supplementing the aging tests already in use (53). At least two laboratory tests are necessary to determine the aging characteristics of natural rubber and GR-S, one using oxygen and the other ozone (56).
Errors in strain measurements are negligible compared with those arising from variations in compounding and vulcanizing, as shown by statistical analyses of data obtained by a new apparatus (38,7 1 ) . Photoelastic analysis is said to be a feasible and reliable method for anticipating design problems in rubber products, since it lends itself qualitatively and quantitatively to the selection of materials, designs, and profiles of products (40). Five methods are described for measuring the complcx differential dynamic Young's modulus of rubberlike materials under conditions of small sinusoidal strain variations, at frequencies from 10-l to IO5 cycles per second, and in a temperature range from -60" to + l O O o C. (58). A method has been described for testing rubber-cord bonds to destruction in shear. The best adhesive for rayon cord was found to be the organic polyisocyanate, Vulcabond T X (50). Plasticity and extrusion index of unvulcsnized mixes, and stress-strain properties, hardness and swelling in hydrocarbon hydraulic fluids, measured after vulcanization, all indicate that variation among lots of a nitrile rubber (Perbunan-18) is no greater than the normal testing error within a particular lot (81). The order of abrasive indexes obtained by the Akron and Du Pont machines is similar. Therefore, the abrasive indexes can be converted from one method to the other by a conversion factor (77). For the determination of tackiness, a rubber mixture is calendered on a fine cotton fabric; a disk of this is placed on a flat elastic support, a strip of the same is placed tight around a cylindrical pendulum hammer, and the latter sct in motion. The recoil elasticity and the number of pendulum beats gives a measure of the tackiness (76). Heat embrittlement can be measured by measuring the extensibility of the sample at an elevated temperature in aE air oven ( 7 6 ) . An improved low temperature brittleness test operates a t temperatures as low as -130" C. (82). The indirect method for total rubber hydrocarbon and the chromic acid oxidation method for determining natural rubber
21 18
INDUSTRIAL AND E N G INEERING CHEMISTRY
hydrocarbon can be used to determine the GR-S hydrocarbon by difference in reclaimed rubber with an error of less than *2.5%, which is considered of practical utility (44). GEhERAL, REVIEWS, AND BOOKS
The effects of bending and shearing have been investigated experimentally for cylindrical shear mountings of various length to radius ratios. The linear relation between torsional couple and amount of torsion of a rubber cylinder is verified within a limited range of strains, and the elastic modulus relating these two quantities is identified with the rigidity modulus obtained in the shear experiments on small deformation (66). The factors influencing the performance of aircraft hydraulic pacltings, n hich have served well under adverse conditions, are discussed ( 1 7 ) . A resume is given of the development, and a detailed discussion is included of the process for the incorporation of carbon black in GR-S latex a t the synthetic rubber plant (46). Review and discussion of present developments, available equipmrnt, advantages and future possibilities of the application of high frequency dielectric heating to rubber and plastics has been presented ( 4 7 ) . A review and discussion of present developments in the injection molding of rubber goods has been given (28).
“Standards on Rubber Products” has been published by the American Society for Testing Materials (1). Description of some important applications of rubber (93); a review, with photographs, of various applications of rubber in architecture and building (57); and an illustrated review of some important developments in rubber suspension systems for vehicles (56) have appeared. “Rubber as an Engineering Material” is a manual describing the basic properties of natural and synthetic rubbers and how thesc properties can be changed for specific applications by various additions and processing procedures (6.9). B book, “Engineering with Rubber” (12), x a s recently published. LITERATURE CITED
(1) American Society for Testing Materials, Philadelphia, “Standards on Rubber Products,” 1948. (2) Anonymous, Chem. Eng. News,27,1729-30 (1949). (3) Anonymous, I n d i a Rubber w o r l d , 120, 342 (1949). (4) Bargmeyer, E. G. (to United States Rubber Co.), C. S. Patent 2,461,953 (Feb. 15, 1949). (5) Bekkedahl, N., Quinn, F. A., Jr., and Zimmerman, E. T.V., J . Research Natl. B u r . Standards, 40, 1-7 (1948). (6) Beu, K. E., Reynolds, W.B., Fryling, C. F., and McMurry, H. L., J . Polymer Sei., 3, 465-79 (1948) ; Rubber C h e n . and Technol., 22, 356-69 (1949). (7) Bloomfield, G. F., J . Soc. Chem. I n d . (London), 67, 14-17 (1945). ( 8 ) Boknia, F. T., Mededeel Rubber-Sticht., Delft, No. 96 (1949). (9) Borders, A . M.,and Pierson, R. M., ISD. ENG. CHE.\f., 40, 1473-7 (1948). (10) Boss, 4.E., Chem. Eng. News,27, 677 (1949). (11) Braendle, H. A., Sweitzer, C. W.,and Steffen, H. C., Rubber Age (S. Y.), 64,708-10 (1949). (12) Burton, W.E., editor, “Engineering with Rubber,” Kew York, hIcGraw-Hill Book Co., 1947. (13) Catton, N. L., Rubber Age (N.Y . ) ,65, 39-42 (April 19491. (14) Catton, X. L., Krisman, E. H., and Keen, W. N., Rubber Chem. and Technol., 22,450-64 (1949). (1.5) Catton, N. L . , and Thompson, D. C., IXD. ESG. CHEM., 40, 1523-6 (1948). (16) Chcm. Eng. -\retos, 27, 1635 (1949). (17) Cheyney, Lay. E., and McCuistion, illech. Eng., 70, 675-9 (1948). (18) Chilton, E. G., J.Applied Mechanics, 15, 362-8 (1948). (19) Cohan, L. H., and Spielman, R., IND.ENG.CHEY.,40, 2204-10 (194s). (20) Conant, F. S.,Dunn, J. L., and Cox, C. XI., Ibid., 41, 120-6 (1949). (21) Crawford, 1%.A . , and Tiger, G. J., Ibid., pp. 592-6. ( 2 2 ) Davidson, IT. L., and Geib, I. G., J . Applied Phys.. 19, 427-33 (194“).
(23) (24) (25) (26) (27)
Vol. 41, No. 10
Davis, C. W., Rubber Age (AV.Y . ) , 60, 573 (1947). Dawson, T. R., Trans. Inst. RubberInd., 24, 227-40 (1949). Dinmiore, R. P., Chemurgic Digest, 8, KO.6, 5 (1949). Donnet, J. B., Rev. 06,. caoutchouc, 25, 172-4 (1948). Frank, R. L., Adams, C. E., Blegen, J. R., Smith, P. V., Juve, A. E., Schroeder, C. H., and Goff, M. M . , ISD.EXG.CHEM., 40, 879-82 (1948). (28) Fraser, D. F., I n d i a Rubber World, 118, 357-62 (1945). (29) Fryling, C. F., Landes, S.H., St. John, W. M.,and Uraneck, C. A., I N D . EKG.CHEM., 41,986-91 (1949). (30) Gardner, E. R., and Williams, P. L., Trans. Inst. Rubber Ind., 24, 284-95 (1949). (31) Garvey, B. S. (to B. F. Goodrich Co.), U. S. Patent 2,443,678 (June 22, 1948). (32) Gehman, S. D., J . Applied Phys., 19, 456-63 (1948). (33) Gillman, H. H., and Thomas, R.. IND.ENG.C m m , 40, 1237-43 (1948). (34) Gongwer, L. F., I n d i a Rubber World, 118, 793-5 (1948). (35) Gould, C. W., Amberg, L. O., and Hulse, G. E., ISD. ENG. C H E Y . , 1025-7 ~ ~ , (1949). (36) Harris, T. H., and Stiehler, R. D., I n d i a Rubber World, 118, 365-6. 371-2 (1948). (37) Hirano, S., and Oda, R., J . Soc. Chem. I n d . J a p a n , 47, 833-4 f 1944). (38) HoiF, L., Knox, E. O., and Roth, F. L., I n d i a Rubber World, 118, 513-17, 578 (1948). (39) Howland, L. H., >lesser, W. E., Neklutin, V. C., and Chambers, V. S.,Rubber A g e (N. Y.), 64,459-64 (1949). (40) Hurry, J. A., and Chalmers, D., I n d i a Rubber WorEd, 120, 199-202 (1949). (41) Ibid., p. 351. (42) James, R. G., Trans. I n s t . RubberInd., 24, 220-6 (1949). (43) Keen, 11’. K.,Trans. Am. SOC.Mech. Engrs., 68, 237-40 (1946). (44) LeBeau, D. S., A n a l . Chem., 20, 355-8 (1948). (45) Levi, F., and Philipp, H. J., Helv. Phys. Acta, 21, 233-50 (1948). (46) Madigan, J. C., and Adams, J. W., Chem. Eng. Progress, 44,81520 (1948). (47) Mann, C., IndiaRubber World, 118, 68-71 (1948). (48) Maron, S.H., and Madow, B., A n a l . Chem., 20, 545-7 (1948). (49) Marquardt, D. N., Poirier, R. H., and Wakefield, L. B., IND. ENG.CHEM.,41, 1475-8 (1949). (50) Martin, G., Rubber Development, 1, No. 5, 4-8 (19483. (51) hlayo, L. R., Griffin, R. S., and Keen, W.N., 1x11.END.CHEM., 40, 1977-SO (1948). (52) Mayor, A. R., and Boissonnas, C. G., Helv. Chim. Acta, 31, 1514-32 (1948). (53) Mesrobian, R. B., and Tobolsky, A. V., IND.ENG.CHEM.,41, 1496-1500 (1949). (54) Mochel, W. E., Salisbury, L. F., Barney, A. I,., Coffman, D. D., and Mighton, C. J., ISD.EXG.CHEhr., 40, 2285-9 (1948). (55) Mooney, M., and Copeland, L. E., J . Applied Phys., 19, 434-44 (1948). (56) Moulton, A. E., Rubber Developments, 1, No. 3, 3-7 (1948). (57) Newton, R. G., Ibid., pp. 16-22. (58) Nolle, A. W., J . AppliedPhys., 19,763-74 (1948). (59) Okita, T., J . SOC.RubberInd. J a p a n , 14, 363-8 (1940). (60) Parkinson, D., Trans. Inst. Rubber Ind., 24, 267-73 (1940). (61) Perry, L. H., I S D . E K G . CHEM.,41, 1438-41 (1949). (62) Puddefoot, L. E., Trans. Inst. Rubber Ind., 24, 199-210 (1948). (63) Raff,Ii.A. Y., Tonilinson, G. H., 11,Davies, T. L., and Watson, W. H., Rubber Age ( N . Y . ) ,64, 197-200 (1948). (64) Reinitz, B. B., and Zaniborsky, N. A., Corrosion, 4, 432-44 (1948). (65) Rhines, C. E., and McGavack, J., Rubber Age (.\’. Y . ) , 63, 599-606 (1948). (66) Rivlin, R . S.,and Saunders, D. W., Trans. Inst. Rubber Ind., 24, 296-306 (1949). (67) Roberts, IC. C., and TTilson, J. (to British Rubber Producers’ Research Assoc.), Brit. Patent 577,472 (May 20, 1946). Kunststofe, 38, 125-30 (1948). (68) Roelig, I%.,and Heidermann, W., (69) Rose, Kenneth, Materials dl. Methods, 27, N o . 5, 93-104 (1948). (70) Rossler, E‘., Z . Angew. Physik., 1, 50-60 (1948). (71) Roth, F. L., and Stiehler, R. D., I n d i a Mubber World, 118, 367-71 (1945). (72) Salomon, G., J . Polymer Sci., 3, 776--S4(1949). (73) Sanders, P. A , Rubber Chem. and Technol., 22, 465-76 (1949). (74) Saunders, D. W., and Treloar, L. R. G., Trans. Inst. Rubber Ind., 24, 92-100 (1948); Rubber Chem. and Technol., 22, 333-41 (1949). (75) Schmidt, E., J . Rubber Research, 17, 196-202 (1948). (76) Scholl, A. W., and Liska, J. W.,I n d i a Rubber World, 115, 663-5, 731 (1947). (77) Scott, J. R., J . Rubber Research, 17, 75-82 (1948). (78) Sell, H. S . , and McCutcheon, R. J., In,dia Rubber W o r l d , 119, 66-S, 116 (1948).
w.
October 1949
INDUSTRIAL AND ENGINEERING CHEMISTRY
2119
(79) Serniuk, G. E., Banes, F. W., and Swaney, M. W., J . Am. Chem. SOC.,70, 1804-8 (1948).
(87) Van der Baan, I., Rubber Developments, 2, No. 1, 20-22 (1949). (88) Wiley, R. H., and Brauer, G . M., J . Polgmer Sei., 3, iO4-7
(SO) Shearon, W. H., McKenaie, J. P., and Samuels, M. E., IND.
(1948). (89) Wilkinson, C. S., Jr., and Gehman, S. D., IND.ENG.CHEM.. 41, 841-6 (1949). (90) Wingfoot Corp., Brit. Patent 613.317 (Nov. 16, 1948). (91) . . Wittbecker. E. L.. Houta, R. C., and Watkins, W. W., IXD. ENG.CHEM., 40,875-8 (1948). (92) Yanko, J. A , J.Polumer Sei., 3,576-601 (1948). (93) Young, H. C., Rubber Deuelopments, 1, No. 4,8-10 (1948).
ENG.CHEM., 40,769-77 (1948). (81) Smith, C. L., and Cheyney, LaV. E., Rubber Age (Ar. Y.), 64, 575-80 (1949). (82) Smith, E. F., and Dienes, G. J., Am. Soc. Testing Materials Bull., 154, 46-9 (1948). (83) Torrence, IM. F., IND. ENG.CHEY.,41, 641-3 (1949). (84) Troyan, J. E., Rubber -4ge (A’. Y.1, 63, 585-95 (1948). (85) Tuley, TV. F., Ibid., 64, 193-6 (1948). (86) Upham, F. N., Trans. Inst. Rubber I n d . , 24, 196-8 (1949).
RECEIVED July 25, 1949.
FIBERS ROBERT S . CASEY, W . A. Sheafler Pen Company, Fort Madison, Zowa
C. S. GROVE, JR. Syracuse University, Syracuse, N . Y .
T
HE United States Department of Agriculture (99) states that cotton, still far in the lead among textile fibers, supplied 57.4y0 of the nation’s textile necds in 1948, amounting to approximatelv 3,500,000,000 pounds. Rsyon consumption climbed tn an all-time high, reaching to more than a billion pounds (1,017,000,000). Other fibers that helped supply textile demands in 1948 included: wool (10% of the total), jute (10.3%), sisal and hemp (60/0), flax (0.2%), and synthetics other than rayon (1%). Unfortunately, these figures do not give industrial and engineering consumption of fibers directly, but it can be estimated that as much as 40% of the total probably is used for these purposes. Rayon, made from regenerated cellulose, \vas the only synthetic fiber in commercial production in this country previous to 1935. Glass fiber was put into production in 1936. About 1938, production of Vinyon was begun, Commercial production of nylon began in 1939. Aralac reached commercial production quantities in 1941; in 1948 a new protein fiber, Vicara, was started in production. Saran was introduced commercially in 1940. Consumption of synthetic fibers other than rayon amounted to a record-breaking 70,700,000 pounds in 1948. Included in this total is consumption of nylon, glass fiber, casein fiber, zein fiber, and synthetic resin fibers (Vinyon and saran). Most of the output of these fibers was continuous filament yarn (65,800,000 pounds) ; the balance (4,900,000 pounds) was cut staple. According to Doiron (39), no completely new fiber, synthetic or otherwise, emerged during 1948. Vinyon S is still in a market testing stage, although commercial quantitieq are available. Orlon is being made in marketable quantities; this fiber has excellent resistance to chemical attack, high thermal insulation, and wrinkle recovery properties; it is, however, more hydrophobic than nylon and may present dyeing difficulties. Vicara (106), a new protein fiber from zein, is said to have superior stability over other svnthetic protein fiber%. Caslen is described by Bendigo ( 1 4 ) as a new casein fiber of more desirable properties. Polyethylene monofilaments (106) again claimed attention in 1948 because they possess good resistance to sunlight, water, arid chemical attack. Properties and applications of synthetic fibers have been enumerated and discussed: Vicara (5, 66); nylon (11, 16, 24, 52, 6 4 , 66, 68, 73, 97, 98); C a s h ( 1 4 ) ; Orlon ( 4 1 , 78); and Vinyon K (81,95). Preparation and properties of elastic nylon have been described by Wittbecker, Houtz, and Watkins (105). Shearer (85) reports the following new or improved uses of synthetic fibers during the past year: Rayon flock has become
useful as a plastics filler and shoe fabric; rayon has made progress in specialty papers, such as tea bag papers and overlay sheets for laminated plastics; Vinyon fibers have been successfully incorporated into a kraft paper with possibilities in the battery separator and floor-covering fields; new machinery has been developed for producing nonwoven fabrics, in which ravon fibers have found wide use; Vinyon N has shown increased promise in the manufacture of filter fabrics; and polyethylene monofilaments have been woven into fabrics for use as upholstery, seat covers, women’s handbags, and shoes. Treatment of fibers, both natural and svnthetic, to improve their properties and to adapt them for sptcialized applications has continued, Cotton has been flameproofed by trcatnient with urea ( 3 ) . Electrically conductive fibers have been prepared by Barnard (19) by impregnation with a cationic agent and colloidal graphite. Various articles (18, 31, 55, 70, 102) report treatments to increase fiber resistance to microbiological attack, Water resistance of regenerated cellulose fibers is improved by formaldehyde (36). Acetylation of zein fibers (44) improves their softness and water stability. Improvements in mechanical resistance to wear of protein fibers have been reported (88) based on impregnation with insoluble chromium compounds. Bogaty (22) reviews improvements in weathering resistance of cotton textiles after various chemical treatments. Jurgens, Reid, and Guthrie (69) state that phosphorylated cotton cellulose becomes a cation-exchange material. Improvement in elastic properties of nylon may be obtained by treatment with vapors of formaldehyde (66). Lipson (67) reviews the literature on production of unshrinkable wool by alcoholic alkali. Considerable research is under way, the Department of Agriculture (9B) reports, to develop additional synthetic fiber< particularly from vegetable proteins and synthetic resins. Orlon and Vicara are two of the newer fibers from this research. Pilot plant work continues on peanut and soybean protein hbers, although neither has been produced commercially in the Gnited States. I n the authors’ opinion, increased emphasis of this research toxvard adapting existing and new fibers for enginc:cxring uses would be very profitable. This is probably of greater importance during the recent recession in demand of tcxtile consumers for fibers. ACKNOWLEDGMENT
The authors gratefullv acknowledge the help of H. L. Glotzer, graduate assistant in chemical engineering a t Syracuse Gniversity, in collecting many of the bib!iographic references.
