October 1948
INDUSTRIAL AND ENGINEERING CHEMISTRY
1809
(77) Shine, W. M., Modern Plastics, 25, 130 (September 1947). (78) Speakman, J. B., and Saville, A. K., J . Teztile Inst., 37, P271 (1946). (79) Stamm, A. J., and Tarkow, H., J . Phys. Colloid Chem., 51, 493 (1947). (80) Stanton, G . W., and Henson, W. A., Paper Trade J.,123, 68 (August 1946). (81) Stott, L. L., Product Eng., 17, 103 (December 1946). (82) Toy, A. D. F., J . Am. Chem. SOC.,70, 186 (1948). (83) Williams, S., Alfers, J. B., and Furgason, C. M., Modern Plastics, 24, 151 (March 1947). (84) Wright, H. J., and DuPuis, R. N., IND.ENO.CHEM.,38, 1303 (1946). (85) Yelton, E. B., Chem. Eng. Progress, 4 4 , 8 9 (1948). (86) Yelton, E. B., Product Eng., 18,164 (November 1947).
Parks, J. D., Benning, A. F., Downing, F. B., Laucius, J. F., and McHarness, R, C., Ibid., 39, 354 (1947). Patterson, J. R., Ibid., 39, 1376 (1947). Patterson, J. R., Oficial Digest Fed. Paint Varnish Prod. Clubs, No. 258 (1946). Pepper, K. W., Barwell, F. T., and Hale, D. K., J . SOC.Chem. Ind.. 65, 153 (1946). Pittenger, J. E., and Cohan, G. F., Modern Plastics, 25, 81 (September 1947). Reed, M. C., J . Polymer Sci., 2, 115 (1947). Reinhart, F. W., Chem. Ind., 62, 235 (1948). Rose, K., Materials &: Methods, 25, 82 (1947). Rowland, G. P., Jr., Cotton, 110, No. 10, 184 (1946). Schaefer, H. L., and Dulmage, F. C., Jr., Modern Packaging, 20, 149 (July 1947). Searer, J. C., Rubber Age ( N . Y.), 62, 191 (1947).
R~WEWED August 18, 1948.
HARD RUBBIER F. S . MALM, Bell Telephone Laboratories, Murray Hill, N. J .
T
H E review of hard rubber developments and the bibliography which was started last year (46) covered 1940 to 1945. This work is being extended by the present review of the literature published during 1946 and 1947. The attached bibliography lists 93 references, most of which have to do with papers and patents relating to uses and methods of manufacture of hard rubber articles. The scarcity of publications dealing with technical studies on the compounding and the physical and chemical properties of hard rubber might be attributed to the fact t h a t hard rubber is a n “old actor” on the materials stage. Being old, respectable, and well known, hard rubber is not likely to be the subject of numerous technical investigations. Our friends in England are largely responsible for advancing the fund of knowledge of hard rubber during the 1946-47 period. A number of their important publications during these years were covered in the review published last year (46). Church and Daynes (26) studied t h e effect of vulcanization temperature on the rate of vulcanization and give d a t a on density, cross-breaking strength, elongation, impact strength, plastic yield, permittivity, power factor, and surface discoloration in sunlight. It is concluded that the selection of the best vulcanization temperature involves a compromise between opposing tendencies in the different properties. Scott contributed two papers (65,64),the first of which is a continuation of theseries on theproperties of hard rubber anddealswith the effect of hydrocarbon oils at high temperature on hard rubber. Data are presented which show t h a t rubber-sulfur ebonites containing 25.8y0 or more of combined sulfur are very little affected by prolonged exposure (67 days) to paraffin or transformer oil at temperatures up to 100” C. Confirming previously published data, the, higher the combined sulfur, the less the sample swells. T h e second paper describes some of the factors affecting color of hard rubber, and results of tests indicate what has been generally understood: t h a t in making light colored hard rubbers, t h e sulfur content should be kept as low as possible and organic accelerators should be used t o lower the temperatures and shorten the time of vulcanization. Continuing t h e British publications, Willott (90)studied the effect of temperature on cross-breaking strength and elongation and concluded t h a t a n appreciable temperature coefficient may exist for the results of cross-breaking tests on a n unloaded hard rubber, but variation in cross-breaking strength within the normal range of room temperature is not appreciable. Davies (24) in a paper first published in 1941 in France but printed for the first time in the United States in 1946, reports on t h e use of accelerators in the vulcanization of ebonite. He
states t h a t the order of efficiency of acclerators varies considerably and is not the same for ebonite as for soft rubber. As with soft rubber, it is possible to increase the efficiency of accelerators by the use of secondary accelerators. Morley (49) has also looked into accelerators in hard rubber and concludes t h a t the vulcanization of a hard rubber containing a high proportion of dust can be shortened by use of organic accelerators. Of the accelerators used, diphenylguanidine appears best when accelerator cost is also considered. Morley’s mixtures do not contain zinc oxide, stearic acid, and other activators. Dock, Scott, and Willott (97) compared t h e properties obtained when hard rubber is cured in a press, in open steam, and in water. Open steam curing is faster than press and water cures. Vulcanizing in open steam increases the water absorption, at least of the outer layers t h a t come in contact with the steam. T h e cross-breaking strength of the steam-cured samples is slightly less than t h a t for t h e press- and water-cured samples, b u t the other physical properties are the same for all three types of cures. Sulfur is lost by volatilization from the surfaces of steam-cured articles. Trillat (’76) studied unvulcanized rubber-sulfur mixtures with radiomicrography, by means of which i t was possible to determine t h e dispersion of sulfur throughout the rubber and the dimensions of t h e sulfur particles. The vulcanization of rubber containing 32% sulfur was followed ,by this process and showed clearly the disappearance of the sulfur particles as the length of cure increased. PHYSICAL TESTING
A number of papers have been presented on t h e physical testing Bailey and Ward ( 2 ) have devised a n impact tester which is simple and inexpensive to build and is satisfactory for small laboratories t h a t cannot afford a n Izod or Charpy machine. Broughton and Willott (11) describe a n improved apparatus for measuring plastic yield. Dock and Scott (g6) compare t h e pendulum (Izod) and falling-weight ( h o d and Charpy) impact machines for testing hard rubber and other materials. There appears to be no great difference between t h e machines in regard to the accuracy of t h e results obtaincd with a given number of test pieces. Attention is called t o the advantages and disadvantages of t h e two machines. Frumkin and Dubinker (5.9) have devised an apparatus for determining the heat resistance of ebonite, and Gurley (3.4) designed a stiffness tester for flexible sheet material. Articles b y R r k e n t h i n (87) describe t h e many specialized tests carried o u t by t h e Bureau of Ships in testing both aoft and
of hard rubber.
1810
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
hard rubber products. Some of the hard rubber product tests referred t o ale. cleavage adhcsion for hard rubber buoyancy material, shaft-covcring adhesion between metal and hard rubber and between hard rubber and soft rubber, and water solubility test of cellular hard rubber for floats. Expanded hard rubber is the subject of 15 references (18, 21, 22, 23, 48,62, 6 ~ $68, > 62, 66,66, 73, 78. 79, 82). During the ~ a expanded r rubber was used for its buoyancy in life preservers and in otheI items connected with navigation and the sea. Now the emphasis is more on the use of expanded hard rubber and plastics in sandwich construction. Such sandwiches, with thin sheets of metal, plastic, wood, impregnated fiber, or fabrics on the outside and cellular hard rubber or plastics as the fillers are, of course, very strong per unit of weight and are finding greater use in constructions where minimum weight is a primary consideration. Following the Armistice in 1945, the Allied Governments sent investigating teams of experts to Germany in order to study the industrial progress which had been made there during the war years. Reports of the various investigations have been published b y the British and American governments. Some of these-(93) published by the British Intelligenre Objectives Sub-Committee and (9, 10, 30, 42, 61, 88, 89) published by the Publication Board, later known as the Office of Technical Services, United States Department of Commerce-relate to various phases of hard rubber production in Germany. Battery boxes and separatois are perhaps the largest uses for hard rubber, and 19 patents and articles relate to these products (12, 14, 19, 26, SO, 35, 36, 44,60, 60,68,72, 77, 80, 81, 83, 91, 92, 93). An illustrated description of the different stages in the manufacture of hard rubber batteries is given (9.9). Miscellaneous patents, government specifications, and publications cover the use of hard rubber in such items as abrasive articles (28) ; atomizing nozzles (58); buoyant electric cables (6); bicycle handle grips (4);combs (7, 29, 4 5 ) ; dentures (86); dielectrics (8); fountain pens (6, 40, 69,61, 7 1 ) ; fuel tanks (d?’); printers’ blocking materials (43); trays (67) ; valves (I) ; and x-ray cassettes (63). Patents were granted for compositions containing mica (37) and boric oxide (84). A British patent describes a thermoplastic vulcanizate (1?), a Belgian patent discloses inand a formation on ebonite and rubber sheets and articles (69), Swedish patent describes a method for dissolving vulcanized hard rubber waste (74). An ebonite type of board made from wood waste is also described (56). A number of books and pamphlets have been published which relate directly or indirectly t o hard rubber. “Reclaimed Rubber” (3)is of interest t o the hard rubber compounder as n-ell as to those in other branches of the rubber industry. “Compounding Ingredients for Rubber” (do), a valuable handbook, gives the properties and suppliers of materials used in rubber. T h e use of plasticizers in hard rubber is discussed (70), and a booklet describes the polishing of ebonite and plastics ( 1 3 ) . “Rubber Red Book” (57) lists hard rubber manufacturers as well as the products they make, and (33)is a catalog of hard rubber products. REVIEWS
Review articles and tabulated summaries of data include Tudor’s review of hard rubber developments (76). “Rubber in Engineering” (56) presents review data on hard rubber with original references. The chemical resistance properties of hard rubber when exposed to corrosive and solvent type liquids are tabulated (16). The use of hard rubber as a material of construction (31) and in modern metal protection for lining and covering equipment subject to corrosion (41) is discussed. The physical and chemical properties of several important classes of plastics and of three grades of hard rubber are tabulated (86). The outstanding properties of hard rubber produced from GR--4 (but adicna-a cr) lonitrile copolymers)-namely, a higher thermal
Vol. 40, No. 10
soltening point arid a higher impact strength-are described briefly (39). The use of synthetic rubber for making hard rubber became mandatory during the war because of t,lie shortage of natural rubber. I n some cases, plants have re!urned to the use of natural rubber, ePperislly where products having flexibility are required. But for many molded arid shaped articles, the synthetic appears to be satisfactory and pvun prcferable, and its continued use seems to be assured. hrtr.rinK a price differential in favor of t h r nafural product,.
(1) Arxnatrow, b’. G . ,231 (June 25, 1.947). Use of hard rubber ill valves. ( 2 ) Bailey, A., and Ward, 0 . W., Am. S o c . T e s t i n g .Ifaterials H u l l . 140, 60-4 (May 1946). Ijaboratory testing of plastics, small
scale impact test.
( 3 ) Ball, J. h l . , “Reclaimed Rubber,” New York, X. Y., IZubber Reclaimers Association, 1947. ..ibook devoted exclusi\rely $0 the subject of reclaimed rubber. (4) Bates, H. T., British Design 845,025 (1945). Cycle handle grip. (,5) Beede, H. L. (to Okonite-Callender Ca,ble Co., Inc.), U. 8.Pat-
ent 2,409,529 (Oct. 15, 1946). Buoyant electric cable. (6) Biro, L. J., British Patent 579,913 (Sept. 4, 1946). Fountain
pen. (7) Bjornsen, 8. S . ,British Design 844,550 (Sept. 2 5 , 1945). Comb. (8) Blokh, G. h.,and Zaionchkovsky, L C Q ~ UProm., UU No. 11/12, 43-44 (1947). Rontgonographic and dielectric investigation of therinorulcanizates (ebonite), (9) Brazier, S.A.. et al., Office of Publication Board, U. S. Dept. Commerce, Washington, D. C., B I O S Final Kept. 349, Item 22, P B 23,858 (October, 1945). Data on manufacture of ebonite and other rubber products. (10) Hrefier, I?’. W., Office of Technical Services, U. S. Dept. Corninerce, Washington, D. C., General Rept. 2, P B 9675 (1943). Review of German patent Merature relat,ing to synthetic rubber, including hard rubber. (11) Rroughton. J. D., and Willott, W.H., J . Rubber Research, 16, 271-4 (1947). Improved apparatus for measuring plastic yield of hard rubber. (12) Brown, F. E., Hignett, A. J., and Redfern’s Rubber Works, Ltd.. British Patent 573,628 (Nov. 29, 1945). Battery boxes with ebonite used to join ot’her rigid materials (laminates or vulcanized fiber) together to form side and base panels. Ebonite is also used to line box. (13) Canning, W.,and Co., Ltd., Birmingham, England, Pub. 792 (1946). Polishing of ebonite and plastics including electrodeposition of metal on plastics. (14) Chapman, E. S., and Pritohett C Gold & E.P.S. Co., Ltd., British Patent 586,072 (March 26, 1947). Electric storage batteries. (15) Chenz. Eno., 53, 120-50 (1946). Chemical resistance of construction metals and nonmetals. including hard rubber. (16) Church, € 5 . F., and Daynes, H. A , , J . Rubber Research, 16, 93104 (1947); Rubber Chem. Technol., 20, 1039-53 (1947). Influence of vulcanization temperature 011 rate of vulcanization. (17) Clark, C . C. (to Mathieson Alkali Works), British Patent 585,783 (March 19, 1947). Thermoplastic vulcanizate. (18) Clark, R. A , , McCuistion, T. J . , and Cheyney, L. E., I n d i a Rubber World, 117, 361-2 (1947). Density, tensile strength, modulus, yield stress, and thermal conductivityoi cellular hard rubber and low density plastics. (19) Compagnie GQnBrale d’Electricit6, German Patent 686,538 (Nov. 1, 1940); abstracted in Rev. Gdn. Caoutchouc, Doc. And., 22, 16 (1945). Microporous ebonite separators for electric accumulators. (20) “Compounding Ingredients €or Rubber,” 2nd ed., New York, I n d i a Rubber World, 1947. Includes information on eompounding materials used in soft and hard rubber. (21) Cooper, A., and Expanded Rubber Co., Ltd., British Patent 573,525 (Dec. 5 , 1946). Ultrafast accelerators make possible use of lorn, vulcanizing temperatures in expanded material production. I b i d . , 578,233 (June 20, 1946). Hydrogen sulfide produced during vulcanization functions as the main blowing agent when expanded ebonite is made using ultrafast accelerators. Ibid., 578,927 (July 31, 1946). Expanded ebonite board for thermal insulation and sound absorption. Ibid., 579,119 (July 24, 1946). Molds of hydraulic cement containing powdered metal for molding expanded rubber. (22) Cooper, ii. (to Rubatex Products, Inc.), U. S.Patent 2,421,831 (June 10, 1947). Single stage production of gas-expanded soft or hard rubber.
October 1948
INDUSTRIAL AND ENGINEERING CHEMISTRY
Cooper, L., and Pfleumer, H. (to Rubatex Products, Inc.), U. S. Patent 2,420,815 (May 20, 1947). Light hard rubber material having a multiplicity of nonconducting cells. Davies, B. L., Rev. Ggn. Caoutchouc, 18, 268-71 (1941); Rubber Chem. Technol., 19,948-55 (1946). Accelerated vulcanization of ebonite. Davies, B. L. (to United Ebonite & Lorival, Ltd.), U. S.Patent 2,406,593(Aug. 27, 1946). Lined ebonite container. Dock, E. H., and Scott, J. R., J . Rubber Research, 16, 104-22 (1947); Rubber Ckem. Technol., 20, 1054-76 (1947). Development of proof impact test for insulating materials. Comparison of pendulum and falling-weight machines. Dock, E. H., Scott, J. R., and Willott, W. H., J . Rubber Research, 16, 266-71 (1947). Influence of method of vulcanization on properties of hard rubber. Comparison of press, open steam, and water vulcanization. Drake, C. E. (to United States Rubber Go.), U. S. Patents 2,418,249, 2,418,250 (April 1, 1947). Abrasive articles. Federal Specification ZZ-C-551a (Feb. 7, 1946), U. S. Government Printing Office, Washington, D. C. U. S.Government requirements for hard rubber combs. Fisher, S. P., Office of Technical Services, U. S. Dept. Commerce, Washington, D. C., 1945. (CZOSItem 1212, File XXXII-811, PB-6675. Manufacture of hard rubber parts for storage batteries and battery ventilating equipment for German submarines. Fontana, M. G., Chern. Eng., 53, 102-5,109 (April 1946). Rubber and plastics as materials of chemical plant construction. Frumkin, L. S.,and Dubinker, Yu. B., U.S.S.R. Patent 66,554 (June 30, 1946). Apparatus for determining the heat resistance of ebonite, plastics, etc. Goodrich Co., B. F., Catalog Section 9405 (May 1947). Hard rubber products. Gurley, W., and L. E., Plastics World, 5, No. 9, 8 (1947) ; Chem. E n g . News, 25, 2847 (1947). Stiffness tester for flexible sheet material including hard rubber. Harding, H. L., and India Rubber, Gutta Percha, & Telegraph Works Go., Ltd., British Patent 582,499 (Nov. 19, 1946). Asbestos improves the shock strength and heat resistance of ebonite. Hardy, C. R., Honey, E. M. O., and Pritchett & Gold & E.P.S. Co., Ltd., British Patent 574,659 (Jan. 30, 1946). Microporous material. Harford, C. G. (to Jefferson Electric Co.), U. S.Patent 2,381,163 (Aug. 7, 1945), same as Canadian Patent 434,892 (May 21, 1946). Hard rubber insulating material containing principally rubber, sulfur, and mica. India Rubber World, 112, 492 (1945). Hard rubber atomizing nozzles for use with acids and other corrosive liquids. Ibid., 117,369-71 (1947). Ebonars, hard rubbers produced from Hycar OR, heat soften at higher temperatures than natural ebonite and have higher impact strength. Jacob, E., British Patents 578,390 and 578,401 (Aug. 10, 1946). Fountain pens. Klein, H. C., Steel, 117, No. 16, 120 (Oct. 15, 1945). Modern metal protection, rubber-lined and rubber-covered equipment. Kongsted, L. P., Office of Publication Board, U. S. Dept. Commerce, Washington, D. C. ( A r m y Air Forces Technical Rept. P 20) P B 2011. Describes process for molding hard rubber parts for magnetos at a plant in Germany. Libberton, H., Photo-Engravers Bull. 35,77-9 (1945). Describes bloclung material with hard rubber binder and filler of ground cork. Lighton, L. E. (to Electric Storage Battery Co.) , U. S. Patent 2,410,952 (Nov. 12, 1946). Heat transfer construction for electrolytic cells. McClure, C. A. (one half t o M. A. Sribike), U. S. Patent 2,387,924 (Oct. 30, 1945). Fountain-type comb. Malm, F. S., IND.ENG.CHEM.,39, 1243-8 (1947). A hard rubber bibliography covering 1940-45 with 270 references. Merrill, J. A. (to Wingfoot Corp.), U. S. Patent 2,424,701 (July 29, 1947). Leakproof fuel cell using a rigid sheet of rubber. Modern Transport, 56, No. 1436, 10 (1946). Use of expanded ebbnite for conveying refrigerated produce. Morley, J. F., J . Rubber Research, 16, 263-4 (1947). Use of accelerators in hard rubber vulcanization. Murphy, R. F. (to Chloride Electrical Storage Co., Ltd.), British Patent 576,324 (March 28, 1946). Plates of electric accumulators. Office of Technical Services, U. S. Dept. Commerce, Washington, D. C., PB 19,331 (August 1937). Applications of Perduren G and H. I. G. Farbenindustrie (in German). Pfleumer, H. (to Rubatex Products; Inc.), U. S. Patent 2,404,594 (Aug. 23, 1946). Reinforced buoyant rubber disk. (53) Powers, F. T., British Patent 587,539 (May 14, 1947). X-ray cassettes.
181 1
(54) Raflovich, H., Canadian Patent 434,439 (April 30, 1946). Vul-
canized blown hard rubber article. (55) Rubber Age (London), 28, 282 (1947). Ebonite type of board
from wood waste.
(56) “Rubber in Engineering,” Brooklyn, N. Y., Chemical Publishing Co., 1946. Data on hard rubber with original references. (57) “Rubber Red Book” 6th issue, New York, Rubber Age, 1947.
Lists hard rubber manufacturers.
(58) Sachs, C. C., iMech. Eng., 68, 233 (1946). Physical data on
expanded GR-S hard rubber, expanded plastics, and sandwich constructions are tabulated. (59) Sattmann, E., and A. W. Faber-Castell, German Patent 744,671. Falling weight made of ink-resisting material for nibs of fountain pens. (60) Schrader, W., Autogene Metallbearbeit., 37, 209-10 (1944) : PZastics (London), 11, 71 (1947). Repairing hard rubber accumulator cases by hot air welding. (61) Schrivener, A., Ltd., Brit. Plastics, 19, 111-13 (1947). Details the centerless grinding method as used in fountain pen manufacture. (62) Schwara, H. F., India Rubber World, 114, 211-12, 219 (1946)Cellular ebonite. (63) Scott, J. R., J. Rubber Research, 15, 179-80 (1946); Rubber Chem. Technol., 20, 171-2 (1947). Action of hydrocarbon oils. on hard rubber at high temperatures. (64) Ibid., 16, 264-6 (1947). Some factors affecting color of hard rubber. (65) Sebrell, L. B., India Rubber World, 114, 388-90 (1946). Properties of cellular materials for sandwich constructions, such as blown GR-A hard rubber, blown GR-S hard rubber, foamed GR-S latex hard rubber, and various plastic materials. (66) Shelmerdine, H. N., and Expanded Rubber Co., Ltd., British Patent 574,448 (Jan. 7, 1946). Thermal insulation employing a combination of balsa wood and expanded ebonite. (67) Smith, L. C. Office of Publication Board, U. S. Dept. Commerce, Washington, D. C. (AAF, Experimental Engineering Section, EXP-M-59-681-44-3), P B 7149 (1942). Hard rubber tray. (68) Smith, W. W. (to Electric Storage Battery Co.), U. S. Patent 2,414,177 (Jan. 14, 1947). Forming oorrugated storage battery separators from microporous rubber sheets. (69) Societe Italiana Pirelli, Belgian Patent 457,183 (Aug. 10, 1944) ; abstracted in Rev, GBn. Caoutchouc, Doc. Anal., 23, 100 (1946). Ebonite and rubber sheets and articles. (70) Standard Oil Co. (Indiana), 910 South Michigan Ave., Chicago, Ill., Circ. 13-16 (Oct. 3, 1947). Indonex plasticizers in hard rubber compounding. (71) Stock, G., British Patent 578,084 (June 26, 1946). Fountain pen. (72) StBckler, L., and Reichswerke A.-G., German Patent 731,482. Mending of cracks and broken parts of hard rubber containers in accumulator batteries. (73) Stulen, F. B. (to Curtiss-Wright Corp.), Canadian Patent 438,901 (Dec. 31, 1946). Propeller blade comprising plates arranged t o form an interior chamber, with porous or cellular material in the chamber. (74) Svensson, O., Swedish Patent 104,698 (June 9, 1942). Dissolving vulcanized hard rubber waste. (75) Trillat, Jean-Jacques, Rubber Chem. Technol., 19, 392-3 (1946). Study of rubber-sulfur mixtures by radiomicrography. “ (76) Tudor, R. J., Ann. Rept. Progress Rubber Technol., Hard Rubber Section, IO, 111-13 (1946). Review of hard rubber developments in 1946. (77) Uhlig, E. C. (to U. S. Rubber Co.), U. S. Patent 2,422,148 (June 10, 1947). Embossed microporous battery separators. (78) U. S. Air Force, Specification R-26,603 (Feb. 20, 1945). Air Materiel Command, Wright Field, Dayton, Ohio. Synthetic hard cellular rubber board for sandwich construction. (79) U. S. Navy Dept., Specification 33 B 3 (Aug. 1 , 1944), U Government Printing Office, Washington, D. C. Buoyant hard cellular rubber. (80) Ibid., 17 B 4h (July 16, 1945). Composition and physical requirements of storage battery boxes. (81) Ibid., 17 C 28 (Aug. 15, 1945). (Also, amendment, Spec. 17 C 28a, Feb. 15, 1946.) Hard and soft rubber parts for use with storage batteries in submarines. (82) Zbid., 33 D 1 (Feb. 1, 1945). Disks of hard cellular rubber. (83) U. S. Rubber Co., British Patent 583,191 (Dee. 11, 1946). Battery separators. (84) Van Nimwegen, G., von Doenhoff, C., and Wooddell, C. E. (to Carborundum Co.), U. S. Patent 2,422,153 (June 10, 1947). Ebonite cured composition including reaction product of a copolymer of butadiene and styrene, sulfur, a fatty acid, boric oxide, and a nonreactive filler. (85) Vulcanized Rubber and Plastics Co., Modern Plastics, 23, 68-9 (1946). Adv. tabulation give$ leading physical and chemical
1812
(86)
(87)
(88)
(89)
INDUSTRIAL A N D E N G I N E E R I N G C H E M I S T R Y
properties of several important classes of plastics and three grades of hard rubber. Wentworth, V. H., Inst. Rubber Ind. Trans., 22, 149-58 (1946). Ebonite dentures made from rubber latex compositions. Werkenthin, T. A , , Rubber A g e , 59, 173-9, 317-23, 446-50, 697-702 (1946); 60, 74-8, 197-202 (1946). Discusses tests used by Bureau of Ships for testing hard rubber and other rubber products. White, W. L., and Schatzel, R. -4., Office of Publication Board, U. S. Dept. Commerce, Washington, D. C. P B 220 (1946). Formulas and manufacturing techniques used in a German plant for lining tanks and making rolls from hard rubber. Zbid., PB 1042 (1945). Description of equipment and methods used in producing rubber-lined steel tanks and molded hard rubber articles in a German plant.
Vol. 40, No.. 10
(90) Willott, W. H., J . Rubber Resezrch, 15, 250-1 (1946): Rubber Chem. Technol., 20,525-6 (1947). Effect of temperature on cross-breaking strength and elongation. (91) Wolff, F., German Patent 745,824. Molded accumulator containers. (92) Young .4ccumulato~ Co., Ltd., Mech. Handling, 32, 674-80 (1948). Illustrated description of stages in manufacture of haid rubber batteries. (93) Yorke, L. E., Spilfogel, C. L., Howell, N. L., Holt, II.,Dowse. J., Bills, E. T., and Spencer, G. D., British Intelligence Objectives Sub-committee, H. M. Stationery Office, London, Final Rept., 767, Item 31, 1946. Accumulator manufacture in Germany. RECEIVED July 31, 1948.
ss Steels
Other Ferr M. H. BROWN AND W. B. DELONG E. I . d u Pont de Nemours & Company, Ine., Wilmington, Del.
R
EVIEW of the literature on stainless steels and other ferrous
alloys for the past year indicates that the results of most of the specialized investigations undertaken to fulfill wartime needs have now been made available. Research in this field csontinues to be very active, however, and important work is currently in progress. Extensive investigations for properly assessing the advantages and limitations of the now commercially available austenitic stainless steel grades containing 0.03y0 maximum carbon are being carried out in several laboratories. Although essentially nothing had appeared in the literature on this subject at the time of preparation of this review, definitive ininrmation should be forthcoming during the next year. Both the 18-8 and 18-8-Mo extra low carbon grades are in limited commercial use. There has been considerable activity in the field of passivity of btainless steels during the past year and important progress has been made toward a better understanding of this phenomeuon. Valuable results have been developed on the effect of heat treatment and modifications in composition on the corrosion resistance and mechanical properties of the conventional austenitic and ferritic stainless steels. Important contributions have also been made in the compilation and correlation of data on the hot gas corrosion resistance and behavior a t high temperatures of the cast heat-resistant alloys. Among the new compositions announced during the year is a wrought stainless alloy of nominal analysis (in per cent by weight) carbon 0.07 maximum, manganese 0.75, silicon 1.0, chromium 20.0, nickel 29.0, molybdenum 2.0, and copper 3.0 minimum. Corrosion resistance appears t o be comparable to cast alloys of similar composition which have gained widespread use, particularly in applications involving the handling of sulfuric acid solutions. Information on the properties of this alloy, including corrosion data, was rex icwrd by Fontana (74). PASSIVITY AND CORROSION RESISTANCE
Important contributions have been made in the study of passivity, oxide films, and related stainless steel corrosion phenomena. Guitton (93-96), who has published several papers dealing with the passivation of the stainless steels, considers that passivity is primarily the result of chemical adsorption of oxygen on the
metal surface. Prior acid corrosion, termed “sensitization,” was reported to accelerate passivation in an oxidizing medium and t o increase its stability toward further corrosion. Uhlig (214, 816) also considers the surface phenomenon of passivity to be one of chemisorption. Iron plated or evaporated over chromium was found to be resistant to nitric acid a t the interface. This is interpreted to mean that intimate contact with chrorniiim alters the reactivity of the surface iron atoms and to providc support for Uhlig’s “clectron configuration” theory. The work of Fontana and Beck (16, 70, 71, 75) has led them to support the hypothesis that a physically adsorbed pas fil~nis responsihle for passivity. Type 301 stainless steel specimens, passivated by exposure to sulfuric acid and then t o air, were found to become active in air-free 10% sulfuric acid o r synthetic sea water after subjection to a vacuum, and again passivc after subsequent exposure to air; this action was completely reversible. By employing a solution of bromine in methanol as a stripping agent, Mahla and Nielsen (139) succeeded in isolating oxide films from austenitic and ferritic stainless steel specimens which had been pickled and exposed to air or to other oxidizing media. Study of the films by means of electron diffraction and microanalytical techniques led to the tentative conclusion t h a t thcir lattice is of the spinel type. Colner (49) reviewed investigations and theories dealing with the passivity of stainless steels and concluded that most of the evidence favored the t,lieory of protection by surface oxide films. The kinetics of the oxidation process of metal surfaces were discussed by Mott (146, 147) and by Gulbransen (97),who enumerated and assessed the importance of eleven fundamental variables. The transition rate theory was applied to the comparison of the oxidation behavior of various metals. Gulbransen, Phelps, and Hickman (98) and Hickman and Gulbransen (101) made an electron diffraction study of the oxide films formed on high temperature oxidation-resistant alloys. No unique oxidation mechanism was shown to exist for Types 301 and 446 stainless steels. The oxides over the complete time-temperature range consisted of chromic oxide or a spinel of unknown composition. Mahla and Sielsen (158) adapted natural oxide films formed on stainless steel surfaces b y oxidation in a molten nitrate bath and stripped by means of a bromine-methanol solution to use as sur-
