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[I/EqMaterials of Construction Review
EIastome rs by B. S. GARVEY, Jr., Pennsalt Chemicals Corp., Wayne, Pa.
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b
Rubber skins for boat hulls have revolutionary implications, not only for marine transportation but also for airplanes and autos
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Coordinated antiskid studies may lead to improved road surfaces and modifications in tire construction to give better skid resistance and reduce rolling friction. Newly developed carbon blacks should help this trend
ODDLY
enough because of technical developments over the past 40 years, there is no longer any generally accepted definition of rubber or rubber products which is adequate for technical, legal, and commercial use. This important question is being studied at length in Committee D-11 of the American Society for Testing Materials. Any chemicals which might be absorbed by foods from rubber articles, such as belts or hose in food processing and distribution, become food additives. This makes food additive law and the Connelly amendment a matter of real concern to many rubber manufacturers and their suppliers of chemicals and other raw materials. Natural Rubber
hs
For the third year, the consumption of natural rubber was greater than its production. Efforts continue in improving yields and quality. The addition product of glycolic acid to natural rubber gives a modification capable of vulcanization by salt-type cross links ( 8 A ) . Either Hevea or balata (gutta percha) hydrocarbons can undergo cis-trans rearrangement leading to the same equilibrium mixtures. With selenium in solution, the mixture was estimated to contain 50 to GQ’% in the cis form ( 7 2 4 . With sulfur dioxide and with certain thiols and disulfides, it was estimated to be 5774 trans (7A). The configurations were determined by infrared spectroscopy. The greater than expected improvement in freeze resistance for rubber treated with small amounts of thiol acids is explained by this isomerization (9A, 7OA). The formation of block and graft copolymers with Hevea rubber con-
tinues to be of great interest whether formed by mastication ( Z A ) , by radiation ( 3 A ) , or by free radical initiation (4A, 5A, 77A, 73A, 75A). By oxidizing off the rubber stem, it has been shown that the molecular weight and molecular weight distribution of the grafts are much the same as for the corresponding homopolymers of acrylate or styrene (6A, 74A).
Diene Rubbers Plans have been announced for building several plants to produce poly(cisisoprene) and/or poly (&butadiene). Production of synthetic rubber in Europe is expanding rapidly and will start in Japan this year. A description has been given of the various types of synthetic rubber available in commercial quantities in Russia (ZB). Their use of 32 million gallons of extender oils in 1959 attests the expanding production of oil masterbatches (3B). Butadiene and isoprene can now be polymerized trans as well as cis (4B, 5B). T h e products are similar to balata; poly(trans-butadiene) is in semicommercial production. A new styrenebutadiene (SBR) latex suitable for foam will encroach on the use of Hevea latex but should improve the position of latex foam us. polyurethane foam ( I B ) .
Other Rubbers
Butyl Rubber. T h e properties of butyl latex have been discussed (75C), as has the compounding of brominated butyl rubber with butyl rubber (3C). The temperature coefficient of vulcanization for butyl rubber was found to be between 1.76 and 2.0 for loo C. in-
crements (74C). The transition metal salts of dithiocarbamic acid had the higher coefficients. Silicone Rubber. The low temperature characteristics of silicone rubbers were related to the flexibility of the chain linkages and the mixtures of methyl and phenyl side groups (77C). A numbcr of new silicone compounds have been announced (7C), and many patents have been reported. Foamed-in-place silicone foams have excellent insulating characteristics (23C). Fibrous matting made of hollow filaments seems to be better than sponge or foam for many types of use (78C). Tapes and sealants extend the use of silicone rubbers. Fluoro Polymers. Copolymers of vinylidene fluoride and hexafluoropropylene of improved quality are available from two sources (9C, 22C). Cure system have been reported, and a mechanism has been postulated, the first step of which is the formation of double bonds in the chain under the influence of a strong base (IOC, 2OC). A variety of elastomeric fluorine polymers and copolymers have been reported, mostly in the patent literature, including those of trifluoronitrosomethane (ZC), hexafluoropentanediol with dibasic acids (77C), trifluoroethyl vinyl ether (79C), trifluoroethyl acrylate with acrylonitrile (72C), and fluorinated dienes (4C). Polyurethanes. While a few reports have appeared on the compounding and properties of polyurethanes (7C, 73C, 76C, 27C), most of the literature in this field consists of a large number of patents and various general comments. There are continued optimistic reports for the future of urethane foams. Other reports cover a continuous process for VOL. 52, NO. 10
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casting solid parts (6C), and processes for casting gas tanks and cable jacket. Polyethylene. Loaded with carbon black and cross-linked by peroxides, polyethylene is a good elastomer for wire and cable use.
Processing Vulcanization. The nature of the reaction, the quality of the products, and the economics of the use of radiation vulcanization have all received attention ( I D , 2 0 , ?'OD, 7 4 0 , 7 8 0 , 2 2 0 - 2 5 0 ) . In butyl rubber vulcanized with resin, the cross link is reported to be the resin itself (300). . 4 diradical is formed at each end of the resin chain by- loss of H-OH. The two diradicals add to double bonds in different molecules of butyl rubber. In thiuram cures, the cross bonds are monosulfides, and in sulfur cures they are polysulfides with carbon blacks increasing the ratio of monosulfides ( 2 9 0 ) . Reversion is attributed to the disruption of polysulfide bonds ( 1 2 0 ) . Part of sulfur vulcanization must be due to polymerization because the loss in unsaturation is greater than can be accounted for by sulfur addition (1SD). Cross linking lowers the melting temperature of natural rubber. Setworks formed from highly ordered chains have a higher melting point than those formed from random chains because of differences in configurational entropy (260). Aging a n d Deterioration. Carbon black does not affect the mechanism of rubber oxidation but may change the rate ( 5 0 ) . Chain scission is considered to be the termination step in a free
radical reaction initiated by hydroperoxides (320). During thiuram vulcanization an intermediate is formed which decomposes, with cross link formation, to form dithiocarbamate antioxidants (90). Antioxidants protect against light, deactivate metal catalysts, destroy peroxides, and stop free radical chains ( 2 7 0 ) . The factors governing ozone attack have been studied by a method involving cut growth ( 7 0 ) . I n the presence of air, but not in its absence, free radicals cause ozone type cracking ( 2 7 0 ) . Antiozonant and antioxidant activity are completely different and may even be incomparible ( 3 7 0 ) . Studies on radiation resistance of elastomers continue ( 7 5 0 ) . Antirads are more effective in the presence of oxygen than in its absence (30, 40). Chain scission during radiation vulcanization is largely temporary and the breaks rapidly reform. Radiation causes high set by forming cross links in the compressed elastomer (60). SBR, neoprene-butadiene (NBR), and a special urethane had the best resistance. Pigments a n d Reinforcement. S e w types of oil, furnace blacks have been announced as combining the reinforcement and compound characteristics of gas, channel blacks with the curing characteristics of oil, furnace blacks. Some grades are equal in tread wear to SAF black and others are interchangeable with gas, SRF black. Attrition of carbon black in ball mills or on rubber roller mills increases the surface area and oxygen content while reducing the pH and structure index (730). Compounding. Reducing the time and temperature of maslication (80)and
attention to the order of ingredient addition ( 7 7 0 ) should improve compound processability and final quality. In general, compound quality decreases as the temperature of cure is raised, but the extent of deterioration varies with the rubber and the curing system (280). Equivalent cures for specimens of diferent thickness have been reported ( 7 ID). Special studies dealt with frosting ( 2 0 0 ) transparent rubber (340), latex masterbatching of dry powders (33D), and rubber to metal adhesion ( 7 6 0 , 350).
Products The Lamiflo coating is a development of great interest and possibly revolutionary significance (77E. 72E). I t is a thin. elastic, and ducted hydraulic skin applied to the hulls of boats and submarines and was developed from a study of porpoises. By changing turbulent flow to laminar flow, it cuts ivater drag as much as 50yc. Because drag consumes over 70% of the driving power, this skin makes possible greatly increased speed or reduced power for marine transport. The principle should also be applicable to reducing air drag of automobiles and airplanes. In the curtain wall construction of buildings, synthetic rubber sealing tapes are used in place of screws (3E). while the glazing and joint sealants may be neoprene sponge (7E) or liquid polysulfide polymers ( 7 E ) . Flood waters in the Los Angeles River are controlled by using an inflated rubber-fabric tube as an adjustable darn ( 6 E ) . Inflatable rubber-fabric tubes are also used for forming concrete pipe in place and for construction of a military rescue airplane. The use of rubber-fabric tanks on flat bed trucks (2E) is increasing, as is the use of rubber-fabric marine barges. Studies of the friction of rubber on various surfaces and its relation to the properties of rubber and the construction of tires have been reported separately (.$E. 5E, 9E, 73E) and in an international conferencr on skid prevention (8E, IOE, 74E). For best skid resistance, the road surface should have suitable projections, and tire treads should have low hardness and modulus and high hysteresis. hlodifications in tire characteristics are needed to combine high skid resistance with low rolling friction.
Bibliography
Courtesy
E. I.
du Pont d e Nemours & Co., Inc
Neoprene collapsible dam across the Los Angeles River
890
INDUSTRIAL AND ENGINEERING CHEMISTRY
Natural Rubber (1A) Bloomfield, G. F., Proc. Inst. Rubber Znd. 6 , 160 (1959). (2A) Ceresa? R. J . , Watson, W. F., T r a n s . Inst. RubberInd. 35, 19 (1959).
a (3A) Cockbain, E. G., Pendle, T. D., Turner, D. T., J . Polymer Sci. 39, 419 11959). \ - - - - , -
(4A) Cooper, W., Vaughn, G., J . Appl. Polymer Sci. 1, 254 (1959). (5A). Cooper, W., Vaughn, G., J . Polymer Scz. 37,241 (1959). (6A) Cooper, W., Vaughn, G., Madden, R. W., J . Appl. Polymer Sei. 1, 329 (1959). (7A) Cunneen, J. I., Higgins, G. M. C., Watson, W. F., J . Polymer Sei. 40, 1 (1959). (8A) Cunneen, J. I., Moore, C. G., Shepherd, B. R., J . Appl. Polymer Sei. 3, 11 (1960). (9A) Cunneen, J. I., Shi ley, F. W., J . Polymer Sei. 36, 77 (19597. (10A) Cunneen, J. I., Watson, W. F., Ibid., 38, 521, 533 (1959). (11A) Elliott, D. J., Watson, W. F., Trans. Znst. Rubber Znd. 35, 62 (1959). (12A) Golub, M. A., J . Polymer Sei. 36, 523 (1959). (13A) Menon, C. C., Kapur, S . L., J . Appl. Polymer Sei. 1, 372 (1959). (14A) Mori, Y., Minoura, Y., K6gy8 Kapaku Zasshi 61, 263 (1958). (15A) Swift, P. M., J . Appl. Chem. (London) 8 , 803 (1958). Diene Rubbers (1B) Chem. Eng. 66, 19 (Nov. 30, 1959). (2B) Rubber World 140, 300 (May 1959). (3B Zbid., 141, 97 (October 1959). (4B{ Short, J. N., Kraus, G., others, S P E Tech. Papers 5, Paper No. 3 (1959). (5B) Vladimirov, A. M., Gavrilova, L. A., Krol, V. A., Kauchuk z Rezina 18, 6 (1959). Other Rubbers (1C) Alzner, B. G., Krisch, K. C., IND. ENG.CHEM.51, 715 (1959). (2C) Barr, D. A . , Haszeldine, R. N., Willis, C. J., J . Chem. SOC.1959, p. 230. (3C) Bluestein, A. C., Grossman, R. F., Rubber World 142, 98 (1960). (4C) Bolsted, A. N., Honn, F. J., others (to Minnesota Mining & Mfg. Co.), U. S. Patents 2,911,396 (Nov. 3, 1959); 2,914,512, 2,914,514 (Nov. 24, 1959) ; 2,915,508, 2,915,510 (Dec. 1, 1958). (5C) Boonstra, B. S. T., Bluestein, A. C., Rubber Age (N.Y.) 86, 450 (1959). (6C) Chem. Eng.6 6 , 4 0 (June 1, 1959). (7C) Ibid., p. 67 (July 13, 1959). (8C) Zbid., p. 22 Nov. 30, 1959). (9C) Zbid.. p. 44 INov. 30, 1959) (IOC) Gallagher, G. A., Eubank, T. D., Moran, A. L., Rubber World 141, 827 (1960). (11C) Gouinlock, E. V., Jr., Verbanic, C. J., Schweiker, G. C., J . Appl. Polymer Sci. 1, 361 (1959). (12C) Halpern, B. D., Karo, W., Levine, P. (to Borden Co.), U. S. Patent 2,834,763 (May 13, 1958). (13C) Klesper, E., Rubber Ape (N.Y.) 84, 84 (1958). (14C) Martin, J. G., Neu, R. F., Ibid., 86, 826 (1960). (15C) Miller, A. L., Powers, K. W., Zbid., 86, 89 (1959). (l6C) Patton, T. C., Ehrlick, A., Smith, M. K., Zbid., 86, 639 (1960). (17C) Polmanteer, K. E., Hunter, J. J., J . Ap,bl. Polymer Sci. 1, 3 (1959). (18C) Russel, R. A., IND.END.CHEM.52, 405 (1960). (19C) Schildrecht, C. E., Brit. Patent 810,513 (March 18, 1959). (20C) Smith, J. F., Rubber World 140, 263 (i959j. (21C) Smith, T. L., Magnusson, A. B., J . Polymer Sei. 42, 391 (1960). (22C) Stivers, D. A., Honn, F. J., Robb, L. E.. IND.END.CHEM.51. 1465 (1959). (23C) Weyer, D. E., Prod.’ Eng. 30, 50 (1959). ~
n
Processing (1D) Anderson, H. R., Jr., J . Polymer Sci. 43, 59 (1960). (2D) Arnold, P. M., Kraus, G., Anderson, H. R., Jr., Kautschuk u. Gummi 12, W T 27 (1 959). \ - - - - I -
(3D) Bauman, R. G., J. Appl. Polymer Sci. 2, 328 (1959). (4D) Bauman, R. G., Born, J. W., Ibid., 1, 351 (1959). (5D) Bevilacqua, E. M., J . A m . Chem. SOC. 81, 5071 (1959). (6D) Blaunshtein, I. M., Berman, M. L., Kauchuk i Rezina 17. 31 (1958). (7D) Braden, M., G‘ent, ‘A. hk., J . Appl. Polymer Sei. 3, 90, 100 (1960). (8D) Carlton, C. A., Rubber World 141, 678 (1960). (9D) Dhnn, J. R., Scanlan, J., J . Appl. Polymer Sei. 1, 84 (1959). (10D) Evans, M. B., Higgins, G. M. C., Turner, D. T., Ibid., 2, 340 (1959). (11D) Freeman, H. A., Gehman, S. D., ’ Rubber Age (N.Y.) 86, 86 (1959). (12D) Gavrishchuk, V. Y., Zubrov, P. I., Vysokomol. Soed. 1, 913 (1959) ; J . Polymer Sei. 41, 563 (1959). (13D) Gessler, A. M., Rubber Age (N.Y.) 86, 1017 (1960). (14D) Harmon, D. J., Zbid., 86,251 (1959). (15D) Harrington, R., Zbid., 8 5 , 963 (,----,I 959).
(16D) Irvin, H. H., S G P Sveiiges Gummitek. Foren. Publ. No. 11, 1 (1956). (17D) Jones, H. C., Rubber W o r d 140, 857 (1959). (18D) Kaplunov, M. Y., Tarasova, 2.N., others, Kauchuk i Rezina 18. 48 (1959). (19D) Klauzen, N. A., Dogadkin, B. A , , Fiz. Sbornik 1957, p. 428; Rubber Chem. B Technol. 33, 208 (1960). (20D) Kluskow, P., Seeberger, E., Kautschuk u. Gummi 12, W T 68 (1959). (21D) Laye, R. W., J . Polymer Sci. 37, 545 (1959). (22D) Mullins, J., Turner, D. T., Zbid., 43, 35 (1960). (23D) Mullins, L., Turner, D. T., Nature 183, 1547 (1959). (24D) Nicolau, C. X., Z. physik. Chem. (Leipzig) 212, 1 (1959). (25D) Pinner, S. H., Intern. J . Appl. Radiation B Zsotopts 5 , 121 (1959). (26D) Roberts, D. E., Mandelkern, L., J . A m . Chem. SOC.82, 1091 (1960). (27D) Shelton, J. R., J . Appl. Polymer Sei. 2, 345 (1959). (28D) Smith, F. B., Rubber World 142, 89 (1960). (29D) Studebaker, M. L., Nabors, L. G., Rubber Chem. & Technol. 32, 941 (1959). (30D) Tawney, P. O., Little, J. R., Viohl, P., Zbid., 33, 229 (1960). (31D) Thelin, J. H., Davis, A. R., Rubber Age ( N . Y . ) 86, 81 (1959). (32D) Tobolsky, A. V., Mercuno, A. J., J . A m . Chem. SOC.81, 5535, 5539 (1959). (33D) Williams, I., Rubber Age ( N . Y.) 86, 460 (1959). (34D) Wolfe, R. F., Steuber, C. C., Ibid., 86, 1009 (1960). (35D) Yamato, T., Tanaka, Y., Sasada, T., Kogyo Kagaku Zasshi 61, 252 (1958). Products 1E Adhesives Age 2, 19 (June 1959). 2E Zbid., p. 33 September 1959). zd., p. 29 {October 1959). Lirtenev, G. M., Styvan, 2. E., Vysokomol. Soed. 1, 978 (1959) ; J . Polymer Sei. 42,283 (1960).
I 1 [E]
(5E) Bueche, A. M., Flom, D. G., W e a r 2, 168 (1958); Rubber Chem. d Technol. 33, 105 (1960). (6E) Du Pont Elastomers Notebook No. 90, p. 677 (October 1959).
y
4 Materials of Construction Review (7E Ztid., No. 91, p. 685 (December 1959). (8E) G‘des, C. G., Saby, B. E., Rubber Chem. G9 Technol. 33, 151 (1960). (9E) Gough, V. E., Engineer 206, 701 (1958) ; Rubber Chem. B Technol. 33, 158 (1960). (10E) Greenwood, J. A., Tabor, D., Proc. Phys. SOC.(London) 71, 989 (1958); Rubber Chem. B Technol. 33, 129 (1960). (11E) Kramer, M. O., J . A m . SOC.Naval Engrs. 72, 25 (February 1960). (12E Rubber World 141, 697 (1960). (13EI Sabey, E ., Rubber Chem. B Technol. 33, 119 (1960). (14E) Tabor, D., Ibid., 33, 142 (1960). Books (1F) Buchan, S., “Rubber to Metal Bonding,” Crosby, Lockwood & Son, London, 1959. (2F) Division of Rubber Chemistry, ACS, Akron, Ohio, “Bibliography of Rubber Literature for 1952-54,” 1959. (3F) Division of Rubber Chemistry, ACS, Akron, Ohio, “Symposium on the Literature of Rubber,” 1959. (4F) Drakeley, T. J., ed., “Annual Report on the Progress of Rubber Technology,” Vol. 22, W. Hefner & Son, Ltd., Cambridge, 1958. (5F) “Elsevier’s Rubber Dictionary in Ten Languages,” Elsevier, New York, 1959. (6F) Gaylord, N. G., Mark, H. F., “Linear and Stereoregular Addition Polymers,” Interscience, New York, 1959. (7F) Houwink, R., “Elasticity, Plasticity, and the Structure of Matter,” Dover Publications, New York, 1958. (8F) Kluchow, Paul, “Die Praxis Des Gummichemikers-Das Laboratoriumsbuch,” Berliner Union, Stuttgart, 1958. (9F) Marvel, C. S.,“An Introduction to the Organic Chemistry of High Polymers,” Wiley, New York, 1959. (10F) Meals, R . N., Lewis, F. M., “Silicones,” Reinhold, New York, 1959. (11F) Morton, M., ed., “Introduction to Rubber Technology,” Reinhold, New York, 1959. (12F) “Proc. 1st Intern. Skid Prevention Conf.,” Virginia Council of Highway Investigations and Research, Charlottesville, Va., 1959. (13F) “Proc. Intern. Rubber Conf., Washington, D. C., 1959,” Division of Rubber Chemistry, ACS, Akron, Ohio, Am. SOC. Testing Materials, Philadelphia, Pa., Rubber and Plastics Division, Am. SOC. Mech. Engrs., New York, N. Y., published by ACS. (14F) “Rubber Red Book,” Rubber Age, New York, 1959. (14F) White, A. W., “Tire Dynamics,” Motor Vehicle Research, Inc., South Lee, N. H., 1959. Symposia and Panel Discussions (1G) Ozone and its effects on rubber, Rubber Age ( N . Y . ) 85, 615 (1959). (2G) Today’s tires-ords, compounding, design, and construction, Ibid., 86, 439 (1959). (3G) Black masterbatches-methods of manufacture, economy, and stability, Ibid., 86, 649 (1960). (4G) Wire-U. S . Army Signal Research ’ and Development Laboratory symposium, Ibid., 86, 667 (1960). (5G) Inorganic, white reinforcement agents, and fillers, Rubber World 140, 263 (1959). (6G) High speed vulcanization by dielectric heating, by extrusion into liquid metal, and continuous vulcanization of wire and cable, Zbid., p. 875. (7G) Materials handling in the rubber factory and the use of rubber in materials handling, Zbzd., 141, 833 (1960). VOL. 52, NO. 10
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