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INDUSTRIAL AND ENGINEERING CHEMISTRY ACKNOWLEDGMENT
The assistance of W. H. Rutter, Electro Chemical Engineering &: Mfg. Co., inthepreparation of thisreview is gratefully acknowledged. LITER.4TUHE CITED
(1) Aima, Ryuzo (to Nippon Rosin Co.), Japan. Patent 3681 (July 13, 1951). Allen, F. H., and Fore, Dan, Jr., IXD.ENG.CHEM.,45, 374-7 (1953). American Cyanamid Co., 30 Rockefeller Plaza, New York 20, N. Y . ,Bull. 4128 (June 17, 1952). Bedwell, M. E., Selected Gout. Research Repts. (Gt. B r i t . ) , 1 (1952), NO. 8, pp. 221-38. Bender, H. L., Modern Plastics, 30, 136-8 (February 1953). B i i t . Plastics, 24, 415-20 (December 1951). Bruner, W. M., and Wayne, P. J., Chem. Eng., 60, No. 7, 193204 (1953). Ceilcoat Co., 4832 Ridge Road, Cleveland 9, Ohio, Bull. 110 (1952). Chem. Eng., 59, No. 9, 196 (1952). Ibid., 59, No. 12, 143-90 (1952). Ibid., 60, No. 6 , 105 (1953). Ciba Co., Inc., 631 Greenwich St., New York 14, N. Y., Bull. 9853 (1950). Ibid., CN501 (1951). Cone, C. N. (to United States Plywood Corp.), U. S. Patent 2,612,481 (Sept. 30, 1952). Council of Scientific and Industria1 Research, Indian Patent 43,320 (Feb. 2, 1952). Craft, B. C., J . Petroleum I’echnol., 4, No. 6, 11-12 (1952). Dadswell, H. E., Fitzgerald, J. S., and Tarnblyn, N., Australian J . A p p l . Sci., 3,71-87 (1952). Dunlop, A. P., and Peters, F. S . , “The Furans,” p. 780, New York, Reinhold Publishing Corp., 1953. Ibid., p. 782. Dunlop, A. P., and Stout, P. R. (to Quaker Oats Co.), U. 8. Patent 2,589,683 (March 18, 1952). Ehlers, J. F., Kunststoffe, 40, 151-7 (1950). Geist, J. hI., Amagna, S. V., and Mellor, B. B., IXD.EXG. CHEW,45, 769-67 (1953).
Himsworth, F. R., and Hughes, Harry (to Imperial Chemical Industries, Ltd.), U. S. Patent 2,592,034 (April 8, 1952). Kalafus, E. F. (to General Tire & Rubber Co.), Ibid., 2,619,445 (Nov. 25, 1952). Keating, P. J., Jr. (t,o Texas Go.), Ibid., 2,614,939 (Oct. 21, 1952).
Klein, Alexander (to Louis S. Werte), Ibid., 2,588,248 (March 4, 1952).
Koroby, J. E. (to Rohm & Haas Co.), Ibid., 2,623,023 (Dee. 23, 1952).
E
Vol. 45, No. 10
(28) Laminex Corp., 994 Jefferson St., Fall River, Mass., B u l l . CRT (1952). (29) Lontz, J. F., and Happoldt, W.B., Jr., IND.ENQ.CHEJI., 44, 1800-5 (1952). (30) McNabb, J. W., and Payne, H. F., Ibid., 44, 2394-7 (1952). (31) hlanaold. G. B.. World Oil.134. No. 6. 112-14 (1952). (32) hIarc-o Chemicals, Inc., 1711 Elizabeth Ave., ‘Linden, N. J., Bull. MR-28C (1952). (33) Massa, A. P., Colon, H., and Schurig, W. F., IND.EXG.CHEX, 45, 775-81 (1953). (34) Modern Plastics, 29, 95-8 (June 1952). (35) Ibid., 29, 80-1 (July 1952). (36) Ibid., 30, 111-99 (January 1953). (37) Ibid.. 30. 96-7 (Februarv 1953). Ibid.: 30: 169 (Ami1 1953). Ibid.; 30; 111-24-(May 1953). Morrow, R. B., Australian Plastics J . , 8, 41-5 (Februarv 1952). hloser, Frank, Ceram. Age, 60, No. 4, 31-3 (1952). Payne, C. R., IND. EKG.CHEX,42, 2030-1 (1950). Ibid., 43, 228G-7 (1951). Ibtd., 44, 2292-5 (1952). Peckman, A. L. (to United States Steel Co.), U. S. Patent 2,597,370 (May 20, 1952). Pennsylvania Salt Mfg. Co., French Patent 970,944 (Jan. 10, 1961). Plastics World, 11, KO.1, 1 (1953). Ibid., KO.1, p. 9 . Ibid.. No. 3, p. 1. Ibid., KO.3, p. 40. Ibid., No. 4 , p. 21. Ibid., No. 4 , p. 29. Powers, P. O., IND.ENG.CHEM.,45, 1063-6 (1953). Preiswerk, E., and Charlton, J., Modern Plastics, 28, 85-8 (November 1950). Quaker Oats Co., Merchandise Mart, Chicago 54, Ill., Bull. 54 (May 1953). Reineck, E. A,, Modern Plastics, 29, 122-4 (June 1952). Ibid., 29, 127-32 (October 1952). Rohm & Haas Co., Washington Square, Philadelphia 5, Pa., BulE. M-7-50 (1950). Seymour, R. B., and Erioh, E. A , Chem. Eng. Progr., 48, 374 (1952). Seymour, R. B.. and Steiner, R. H., Ibid., 48, 430 (1952). Sheehan, G. M., Kraus, Gerard, and Conciatori, A. B., IND. ENG.CHEW,44, 580-2 (1952). Shell Chemical Corp., 500 Fifth Ave., New York 36, iK. Y . , Bull. SC-51-21 (1951). Ibad., SC-52-39 (1952). Sterne, W.P., Oil Gas J., 51, KO.9, 72-3 (1952). Thiokol Corp., 778 North Clinton Ave., Trenton, N. J., Bull. LP-2 (1953). Thompson, A. F. (to Minnesota Mining & M f g . Co.), U. 5. Patent 2,610,910 (Sept. 16, 1952).
S
5
HARRY L. FISHER Unicersity of Southern California, LOS Angeles 7 , Calif
The matter of proper disposal of the government synthetic rubber plants to private industry is the most important news i n the synthetic rubber field. These plants are not war surplus but are of real use in our national security. When this is printed the disposal will probably be well along. Sixty-five per cent of the GR-S now produced is cold rubber, manufactured at 41” F. About 900,000 long tons of synthetic rubbers are being manufactured this year in this country, and 400,000 long tons of natural rubber will be imported. Oil-plasticized high viscosity synthetic rubber continues to be of importance and is now a regular article of commerce. Chemigum S L is a new synthetic rubber based partly on the German Vulcollan; it has tensile strength of over 5000 pounds per square inch without carbon black, good resistance to abrasion, and high tear strength.
T
HE Office of Synthetic Rubber of the Reconstruction Finance Corp. presented t o President Eisenhower its “Program for Disposal t o Private Industry of Government-Owned Rubber-
Producing Facilities” (112). This was in accord with Congressional action and received the President’s approval. The Paley Commission chapter on rubber predicts that the world need for total rubber in 1975 will be 3,300,000 long tons, and that 2,500,000 long tons of total rubber will be used in the United States, of which 50 t o 60% will be synthetic (134). The price of the synthetic G R S and Butyl rubbers may then conservatively be placed within striking distance of 20 to 25 cents a pound in 1950 dollars, including profit margin. The commission
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INDUSTRIAL AND ENGINEERING CHEMISTRY
estimates that probably synthetic rubbers in 1975 will be derived principally from n- and isobutylene, acetylene, ethylene, and aromatics (60). NATURAL RUBBER
-+
I n hot mastication, plasticizing is caused by oxidative reactions, but in cold mastication, plasticizing is due to a primary rupture of the long-chain rubber molecules by the applied deformation forces and to a secondary consummation of this rupture by oxygen or other compounds reactive toward the ruptured chains (191). Both p-benzoquinone and azobenzene, under nitrogen, lower the cold mastication plasticity. Aqueous emulsions of xylenethiol and its zinc salt are particularly effective in conjunction with sodium bisulfite for eliminating the yellow coloring ingredient in natural rubber latex (168). There is a general discussion, including photographs of sampling, on recent progress in providing technically classified natural rubber (132). About 25,000 long tons are being classified this year, and it is likely that the Mooney viscosity test will be dropped and only the vulcanization characteristics kept. A report has been published about the dirt content of crude natural rubber, its determination, content of trade grades, its elimination during preparation, and iiifluence of packing and bale coating (76). Natural rubber produced under the greatest care is free from harmful dirt, but contains from 0.15 to 0.4Oyo total dirt, which is made up of natural components of the latex. The activities of the Institute of Rubber Research in Indochina cover improvements in productivity and uniformity of Hevea, treatment of diseases, analysis of latex, technical classification of rubber, and preparation of special types of rubber (37). The durability of natural rubber is shown in a number of instances, especially rubber-covered batcher rollers that have carried 500,000,000 yards during 25 years, a transmission belt that has been taken up less than 1% in 21 years, an ebonite pipe in good condition after handling vinegar for 67 years, and a bank floor still good after 55 years (162). Fundamental data on rates of diffusion for a large-scale extraction apparatus for guayule show that the extraction of resin under controlled conditions conforms fairly well with the Fick law of diffusion (10). Pilot plant experiments have shown that rubber of uniform high quality can be prepared from the tiny guayule "worms" by deresination with acetone (54). A considerable increase in the formation of guayule rubber takes place if acetic acid and acetone are added t o the nutrient solution in which tissues or seedlings are growing; these two substances probably react t o form P-methylcrotonic acid which also can result from acetoacetic acid as an intermediate, because it decomposes into acetone and acetic acid (88). Sorva (Couma guianensis) consists chiefly of 70% of resinous substances and 3Oy0 of a rubberlike substance, and the latex has been used only as a binder in road pavement (66). NEW MONOMERS AND NEW SYNTHETIC RUBBERS
Chemigum SL is an elastomeric polyester-urethane based on the German Vulcollan (161). It is prepared by condensation polymerization of a low molecular weight polyester adipate with a diisocyanate. I t s gum vulcanizate tensile is 5000 pounds per square inch, elongation, 750%, and abrasion resistance twice as great as that of the best cold rubber. Benzalacetophenone and other a,@-unsaturatedketones copc&merize readily in recipes with 1,3-butadiene, isoprene, and styrene (119). The copolymers of butadiene and benzalacetophenone show good tensiles with hysteresis properties somewhat better than the corresponding butadiene-styrene copolymers, Copolymers of various acrylic esters, from ethyl to octyl, with 5 t o 15% acrylonitrile or methacrylonitrile, were prepared by re-
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fluxed emulsion polymerization and in two instances by redox polymerization, all of which were easily vulcanized with sulfur and triethylenetetramine recipes (64). The products are heatresistant and have brittle points around -45' F. The evaluation of the butadiene-butyl vinylsulfonate copolymers indicates that these synthetic rubbers have good low temperature characteristics and that the stress-strain properties approach those of standard GR-S rubber; however, the oilresistance is poor (118). Vinylcyclopropane is obtained by the dehydration of methylcyclopropylcarbinol over alumina at 265' and 300' C., the yield being as high as 54% (164). In the condensation of methylal with diolefins the methoxy and methoxymethyl groups are added in the presence of boron trifluoride; butadiene produces a variety of products including 3,5-dimethoxy-1-pentene and 1,5-dimethoxy-2-pentene (44). Thermal dimerization of 1,3-butadiene at 775" F. and about 60 pounds pressure gives a high yield of the 1,2- addition product (4-vinyl-1-cyclohexene) and 7,5y0yield of the 1,4- addition product (1,5-cyclo-octadiene) (79). Isomerization tests on 1,5cyclo-octadiene at 800" C. gives complete conversion to butadiene, vinylcyclohexene, and polymers. The Jersey process of commercial dehydrogenation of butenes gives from 0.5 t o 1% of carbonyl compounds, which have been found to consist of 60% acetone and 24% methyl ethyl ketone
(66). Trimethylethylene, obtained by the thermal decomposition of natural rubber, when treated with sulfuric acid gives isodecene, which was hydrogenated t o isodecane (18%). OTHER SYNTHETIC RUBBERS
There is published a brief history and description of the process for the manufacture of Vulcollan, which is the synthetic rubber prepared from adipic acid and ethylene glycol, followed by reaction with a diisocyanate, and cured with addition of more diisocyanate, glycol, or diamines (130,140). The chemistry of Hypalon, the chlorosulfonated polyethylene with about 27.5% chlorine and 1.5% sulfur, is given in greater detail than previously published, and many uses are also indicated, especially with blends, because it has unusual durability on exposure to ozone, oxygen, heat, and weather (64). The cure of chlorosulfonated polyethylene is believed to be the reaction of metal oxides with the sulfonic acid group formed by the hydrolysis of the sulfonyl chloride group (167). A practical gel test for screening potential curing agents has been demonstrated for chlorosulfonated polyethylene and a number of organic curing agents found (50). In a gum stock, the highest tensile strength was produced by 2,5-hexanedione dioxime, and in a compounded stock by thiourea. Reinvestigation of the structure of the polymers of alkyl OLhaloacrylates has proved that they have predominantly the headto-tail structure instead of the earlier assignment of a head-tohead arrangement of the monomer units (120). A description is given of the alfin rubbers, the catalyst, possible mode of action, and properties (127). The alfin catalyst hitherto was considered t o be a combination of allylsodium and sodium isopropoxide, but it has been found that a halide or pseudo-halide salt is essential (168). The,aodium cation is required for the catalyst. The potassium ion can be tolerated in the alkoxide or halide but not simultaneously in both. The alfh polymers have a high proportion of 1,4- configuration and an abnormally high intrinsic viscosity. I n polymerizations by sodium, associated salts may affect the reactions of the amylsodium either by accelerating the dissociation to radicals or by providing appropriate positions for absorption of a reacting molecule (169). A long article gives further data on the use of the alfin catalyst for polymerizing butadiene and butadiene-styrene (172). It is not necessary t o use highly purified butadiene, and oil and carbon black
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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
Vol. 45, No. 10
these oils, differ in their effect on rate of polymer breakdown or condensation, or on the change in Mooney viscosity (178). The differences in the function of oils in high Mooney viscosity GR-S masterbatches are caused by differences in chemical composition of the oils, which are not fully defined by the analysis determining per cent composition in terms of asphaltenes, nitrogen bases, acidafins, and paraffins. Attempted correlation of the various effects obtained with physical constants such as gravity, viscosity, viscosity index, or bromine number of the oils does not show ariy obvious interrelationships. A very good discussion of the hydrocarbon composition of rubber processing oil8 has been published (104). POLYMER1 ZATIOK
GR-S, comparable t o standard hot rubber, has been prepared at 122' F. with a reaction time of 15 to 20 minutes in pilot-plant quantities in a New Utility Solvent Extractive Distillation Section a t Neches Butane continuous process polymerizer conProducts Co. Butadiene Plant at Port Neches, Tex. sisting of 382 feet of 5/&1ch tubing with a volumetric capacity of 4.9 gallons (52). The flow was essentially of the streamline type; turbulent flow was shown to can be used to soften the pol>-mers. Intrinsic viscosities of over be unnecessary. Cold rubber (GR-S polymerized a t 41" F. 20 mere obtained. to 60% conversion) can be prepared in this equipment but OILPLASTICIZED SYNTHETIC RUBBERS not without using higher-than-normal proportions of water and soap. The seventh foundation lecturer, R. P. Dinsmore, of the InIn a report on polymerization of GR-S at low? temperatures stitution of the Rubber Industry, discussed the economic and recipes are given for the standard formula at 41 O F., and for variaphysical aspects of GR-S modifications and stressed the increase tions at 0" F. and 41' F. (88). Presence of methanol gave lower in tread wear by the addition of petroleum oils to the hot and the physical properties. Recipes are also included for 60% convercold types of GR-S (45). sion in 5 hours and in 1.67 hours at 41' I?. Laboratory studies on the processing of oil-extended and carbon A resume is given of the methods used in reducing the reaction black G R S masterbatches show that the flex-crack resistance time in t h e preparation of GR-S at 41' F. from 23 t o 9 hours, reaches a maximum with a definite Banbury mixing cycle after chiefly b y the careful exclusion of oxygen, activator preparation, which additionaI mixing causes reduced flex-crack resistance (51). use of more active hydroperoxide initiator, and use of metal comCopolymers of butadiene and styrene prepared at 41 'F. to high plexing agents (149). Mooney viscosities have been extended with various rosin-type A full report is published on the history, preparation, properacids in a manner similar to that employed in extending with petroleum oils by latex masterbatching or by polymerizing in the ties and evaluation of diazo-initiated polymers (196). Nitra, presence of large proportions of rosin-type emulsifier (89). zole C F is a stabilized sodium diazotate salt of p-nitroaniline, and Laboratory evaluation of these products has shown that they without the use of a modifying agent it gives a GR-S copolymer have properties equivalent t o oil-extended polymers, as much as at 122' F. that is approximately the same as the usual GR-S at 50% better Lambourn abrasion resistance than regular cold 41" F. rubber vulcanizates, up to 15' C. lower temperature rise on flexI n GR-S polymerization the anionic emulsifiers (sulfates and ing, superior flex-craclung resistance, and superior aging resistsulfonates) generally provide good conversion rates with adequate ance. latex stability ( 7 7 ) . Cationic emulsifiers (quaternary ammonium Relatively aromatic oils can be mixed faster and better into salts and amine salts) yield poor conversion ratesat41 O and 122"F. high Mooney viscosity polymers than the relatively naphthenic but generally fail t o stabilize the latex adequately. Of the oils, which in turn are better than the relatively paraffinic oils nonionic polyoxyethylene glycol derivatives tested, only the (193). Practically all the oils tested could be used commercially, amides, at favorable pH levels, are approximately equal to the although difierences in incorporation and processing can only be sodium fatty acid soap control in conversion rate and stability. attributed to chemical structure. Tire test results also indicate Ethyl maleopimaric soap (disodium soap of the maleic anhythat the chemical composition of the oils had very little effect on dride addition product of ethyl levopimarate) is a satisfactory the abrasion resistance and serviceability of oil-enriched rubbers. emulsifier for GR-S polymerizations (69). The addition of the Compatibility, processability, and low temperature properties maleic anhydride converts the conjugated double bonds into a are the most important factors to consider in selecting the petrosingle double bond which does not inhibit addition polymerizaleum oil for high viscosity rubbers. tion. By means of infrared absorption i t has been demonstrated It has been shown that various commercial petroleum oils in butadiene-styrene copolymers that, as the content of styrene used in masterbatching high Mooney GR-S, as well as fractions of
October 1953
INDUSTRIAL AND ENGINEERING CHEMISTRY
is increased, the percentage of trans-l,4 addition increases, the
1
1,2- addition decreases, and the cis-l,4 addition decreases (60). ~-Benzoyhrinylphenyl sulfone is an active dienophile, giving adducts with cyclopentadiene, 2,3-dimethylbutadiene, isoprene, and butadiene in excellent yields (168). They are obtained only as high boiling viscous oils, but crystalline dibromides or dinitrophenylhydreaones are readily formed from them. Aliphatic mercaptans, containing 6 t o 12 carbon atoms, solubilized in sodium iaurate solution in the presence of potassium persulfate add t o unsaturated compounds by a chain reaction (103). In Q study of the mechanism of initiation of emulsion polymerization by persulfate, it is shown that sulfate free radicals are produced only by thermal dissociation of persulfate (102). A new redox recipe hEba been described for the polymerization of (75 :25) butadiene-styrene with ferric versenate, sodium sulfide, and a hydroperoxide as the activating system, and called VeroxasuIfi.de recipe (101). It gives 85% yield in 12 hours at 5’ C. (41” F.), and needs no thiol for initiation. Added oxygen has only a slight effect, and it can be eliminated by the addition of sodium dithionite. I n the relationship between the vulcanization variables and yield of cross links it is shown that when these variables are controlled in such a way as t o give the greatest yield of cross links, a definite relationship exists between physical cure (stress a t 200% elongation) and combined sulfur (12). I n the free-radical emulsion polymerization of butadiene and styrene, a combination of 0.05 part of sulfur and 0.03 part of sodium dimethyldithiocarba mate is a mitable shortstop agent for a 41’ F. oxidation-reduction system (8). l-Cyclohexyl-l,3-butadienereacts with sulfur dioxide t o give both a cyclic and polymeric sulfone; 1-p-nitrophenylbutadiene formed a cyclic sulfone, not a polysulfone, while l-p-anisylbutadiene formed neither (73). LATEX
Addition of the h c salt of mercaptobenzimidazole t o heatsensitized latex avoids most of the inconveniences that are encountered in present-day procedures; its compatibility and heatsensitizing action is permanent and is not diminished by the presence of other agents (&). Zinc oxide need not be present, and there is no effect on the color. Present-day natural rubber latices are much more stable in contact with zinc oxide than those available before World War I1 (92). Latex stability is determined by a mechanical test for measuring the strength of wet latex gels
(115).
*
16
The weight average particle sizes of 22 synthetic latices range from 730 t o 3920 A. by electron microscopy, and the latices were all nonhomogeneous in size distributions both on a number and weight basis, which in some instances contained single and in some cases double maxima (117). The particles in unconcentrated latex, examined by electron microscopy, were practically spherical (181). The skin of centrifuged and ranged from 0.05 to 1 . 1 ~ latex contained no particles above 0 . 4 5 ~ ;hence centrifuging is an effective way t o obtain latex containing only relatively small particles. Ammonium hydroxide reduced the volume of “lutoids” or “viscoids” just as sodium sulfite did, and disintegrated the viscoids into small units and set free the Frey-Wyssling globules embedded in the viscoid complex (186). (Formaldehyde retards the separation of viscoids and increases the volume.) Even in very low concentrations formaldehyde is highly effective in causing separation of the viscoid fraction from latex. A method is described for determining the volume changes of an elastomeric latex cast cylindrical film from measurements of the length, height, and thickness of a flat sheet cut from the cylindrical film; a nomograph is included for simplifying the calculations (2). In a study of the tensile properties of films from low t e m p e m ture GR-Slatex, it was found that microscopic coagulum had a
2191
pronounced effect in decreasing the film tensile of vulcanizates and that the incorporation of small proportions of lignin into the latex decreased cure rates of films but aided reproducibility (25). Poor films are composed of discrete individual particles, whereas in a continuous transparent film the particles have coalesced into a polymeric mass, according t o an electron-microscope etudy of plasticized latices ($1). The manufacture of ebonite objects from latex is described (108), and the superior mechanical properties of such products in comparison with those from corresponding dry rubber mixtures is ascribed t o the retention in the latex process of the original length of the rubber molecules (81). BUTYL SYNTHETIC RUBBER An interesting review of the evolution and application of Butyl rubber has appeared, including the characteristics of ionic polymerization and the use of Butyl rubber in inner tubes and such other fields as proofed goods, electrical insulation, and mechanical goods (1). The excellent heat and age resistance, high resistance t o gm permeation, and good tear resistance of Butyl rubber have contributed t o improving the fundamental adequacy of pneumatic inner tubes so that Butyl rubber has almost completely displaced natural rubber for that purpose (86). The raw tenacity of Butyl compounds is improved by introducing a minor degree of scorch during the early stages of mixing by small additions of very active cross-linking materials, such as p-dinitrosobenzene (Polyac). The basic iodine-mercuric acetate method for Butyl rubber unsaturation has been improved by the standardization of reaction conditions, and a correlation between unsaturation and stressstrain values in the National Bureau of Standards formula has been developed (40). Reliable results suitable for control purposes are available in 3 t o 4 hours, and improved product uniformity is obtained. The impregnation of leather with Butyl rubber is well suited for shoe soles and upper leather since it reduces water absorption by about half and doubles the abrasion resistance (164). SILICONE RUBBERS
The polysiloxane chain in polydimethylsiloxanes consists of identical bonds of length .I meeting a t angles e, and 82 which alternate along the chain (59). The molecular dimensions of fractions of four samples of polydimethylsiloxanes, memured by osmotic and viscosity methods, varied from 52,500 t o 685,000. Various organic azo compounds catalyze the heat conversion of polymerized organopolysiloxanes t o solid elastomers (silicon rubbers) having improved heat-aging properties-for example, CHs CHs
I
I
CH3N: NCHa and NC.C.N: N.C.CN (46). LHa (!!HI Properties, studied with a new apparatus for obtaining stressstrain curves a t temperatures down t o -130’ F. and lower, showed the superior behavior of silicone rubbers a t very low temperatures, since neither of those tested stiffened appreciably until it reached a temperature range of -112’ t o -130’ F., whereas the natural-rubber and GR-Svulcanizates were stiff at -76’ F.
(139). In a study of the compounding of silicone rubber, physical properties are given for vulcanizates with silica Aerogel pigment (Santocel C), titanium dioxide pigment (Titanox RANC), aluminum oxide pigment (Alon), and coated silica pigment (Du Pont GS-lSQS),which latter produced tensiles up t o 1900 pounds per square inch, elongation of 625%, and Shore hardness A of 68 (169). Many of the unusual properties of siloxane polymers stem from a single structural feature and a single chemical phenomenon
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INDUSTRIAL AND ENGINEERING CHEMISTRY
(190). The structural architecture of the coiled helix type of pol-
ymer accounts for many properties: the intrachain forces of internal rotation-bending, stretching-control stiffness, the ability to coil and their modifications result when the oxygen is replaced by other atoms and groups. The effects of chemical groups are also shown and discussed under interchain forces which are those of slipping, sliding, and gliding and represent the effect of polymer molecules on their neighbors. Silastic XC-270 is an adhesive that retains its adhesive strength from -55" t o over 300' F. (157). Production of Silastic rubbers is now over 500,000 pounds per month. PHYSICAL PROPERTIES
A study of the action of the Mooney viscometer under different conditions by the National Bureau of Standards has brought forth the following recommendations: 1. Radial V-grooves should replace the serrations on the rotor and the dies. 2. Chromium plating of the rotor and dies should be eliminated. 3. Die and die holder should be constructed as an integral unit. 4. The speed of the rotor should be reduced to 0.1 r.p.ni. or less for rubbers having very high molecular weights (42).
The most noticeable difference between rubbers polymerized a t low temperature and a t high temperature was that the former shoved a greater increase in non-Kewtonian character with increasing solution concentration, the effect being observed only a t concentrations above 70% in 1-methylnaphthalene with a McKee worker-consistometer (15). A list of plasticizing agents for nitrile rubbers consists chiefly of esters of N,N-dialkyldithiocarbamic esters, alkyl carbamates, substituted amides and imides, acylated amino hydroxy compounds, and esters of hydroxy-methyloxazolines (31), A fair proportion are excellent: butyl-Ar,N-dibutylcarbamate (somewhat low b.p., 256' C.), 12'-butyIauccinimide, and 2-caproamidobutanol. The important factor in any characterization of vulcanizates for resistance to low temperatures is the effect that the time of storage at lorn temperatures has on crystallization and yield of stress (28). The existence of a state of crystallization is not so important as its development during prolonged exposure a t a low temperature or its reorientation under an applied stress. The continuous stress relaxation has been followed on vulcanizates of natural rubber, GR-S, Neoprene-GN, and butadieneacrylonitrile copolymer, each containing SRF black, in the presence of three different petroleum oils a t room temperature and at 70" C. as a function of time (IS). In contrast to the acceleration of stress relaxation of rubber exposed continuously t o oil but intermittently unstressed, continuous stress relaxation gave different results. In some cases, after 5000 hours, the stresses exceeded the initial stresses and in all cases were equal to or greater than corresponding values in air. Investigations of the rheology of moderately concentrated rubber solutions using the McKee consistometer have provided flow data on three substances at higher shearing stresses and rates of shear than heretofore possible with conventional viscometers (153). It has been calculated that the free energy of rubber is equal to the s u m of the free energy of the chain network aithout interactions (18). A liquid formed of the chain elements alone, minus the free energy of a perfect gas having the same number of molecules as the rubber, has chain elements. I n the reinforcement of rubbers i t is believed that, although some evidence indicates the formation of chemical bonds between polymer and filler, the major part of the reinforcing effect is still attributable t o van der Waals forces, the energy spectrum of which depends on the chemical and stereo conditions of the filler surface (80).
Vol. 45, No. 10
Neoprene vulcanizates have been designed that, in tests over 10 years, show resistance to creep equal t o or better than that of natural rubber (95). Experiments with different plasticizers have shown that there is no direct or simple relation between the freezing points of plasticizers and the freezing points of elastomers plasticized with the corresponding plasticizers (138). Particularly great freezingpoint depressions should result from blending compounds having dissimilar structures and different attractive forces. The most effective compounds found for accelerating the plasticization of rubber were aromatic thiols, 2-naphthalenethiol, and xylenethiol, although 1 atom of sulfur, selenium, or tellurium per 20 molecules of xylenethiol causes total inhibition (126). From the combining ratio of monomers in emulsion systems at 5 O C., a t low conversion$, the reactivity ratios of the copolymerizing pairs were calculated, and estimates of the values of Q and e for butadiene, isoprene, and dimethylbutadiene were made ( 6 6 ) . Vapor-liquid equilibria data were obtained by a static method over concentration and temperature ranges of practical interest, such as methanol Concentrations up to a mole fraction of 0.17 on a methanol water basis, styrene concentrations up to a styrene t o polymer ratio of 0.166, and a temperature range of 30' to 9.5' C. (49). Swelling measurements of polymers in solution can be a useful tool in obtaining vapor-liquid equilibria for polymer-solvent systems, at least for systems which are nonpolar. Rubber compositions (100 parts) mixed with 20 to 75 parts of polyethylene and an electrically conductive black (40 to 150 parts), with the usual compounding ingredients, have a specific resistance of 100 ohm-cm. or less a t 20" C., and the resistivity does not increase after flexure (115). In a further study of electrical contact potentials in Banbury mixing, application of the electrostatic contact potential theory of mixing, which involves the attractive forces between the positive pigments and the negative rubber in promoting rapid incorporation and the uniformity of electrical charge on pigments in promoting good dispersion, has resulted in the production of coated zinc oxide pigments that produce better quality stocks a t reduced mixing costs (75). Pure neoprene is a polar elastomer showing two fields of dispersion which are partially superposed, according to a dielectric study (147). An apparatus has been designed and built for using the electrical analog method for studying elastomer behavior and testing models of all types of polymeric materials ( 1 7 1 ) . It should prove particularly valuable in developing nonlinear models that are difficult to build and test in the mechanical system. Experimental data have been presented on the stress-relaxation modulus E , T ( ~of) a GR-S gum vulcaniaate a t a series of temperatures in the transition region and proper curves constructed ( 1 7 ) . The sample is maintained a t a constant small strain for a time, t . .4 differential refractometer that satisfies safety requirements and gives reliable indications of changes in index of refraction to 0.001 unit or better has been developed for use in outdoor process plant locations (124). Neoprene Type RT mounts should not be used for vibration isolation in applications where the mounts would be exposed for long periods of time to moderately high temperatures, because of excessive drift, or t o moderately low temperatures, because of excessive drift and excessive stiffening (126). The mean value of the heat of polymerization of butadiene is given as 17.4 kcal. per mole, and the values obtained for the heat of copolymerization varied from 17.1 t o 17.7 with no obvious trend (151). The velocity and attenuation of ultrasonic waves have been measured as a function of temperature in specimens of a nitrile rubber vulcanizate swollen t o various degrees with methyl ethyl ketone (133). The frequencies were 2, 5, and 10 megacycles. By decreasing the styrene content from 25 to 0 parts in sodiumcatalyzed polymers the freeze point was decreased from -26" for 75: 25 butadiene-styrene copolymer to -47 O C. for polybutadiene
October 1953
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I N D U S T R I A L A N D E N G I l? E E R I N G C H E M I S T R Y
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(145). Because the electrical properties of the sodium polymers are good, this type of polymer could be used advantageously for wire and cable insulations. The polymers are prepared only on a pilot-plant scale. A clarification is discussed of the currently prevalent confusion with respect to the theory of rubber elasticity (188). The configurational entropy of vulcanization must be zero and quite independent of the statistieal nature of the chains comprising the network, providing the network is not deformed macroscopically. A rapid and inexpensive method has been devised for measuring diffusion coefficients of high polymers in solution (189). The method consists essentially of soaking a porous disk in the solution and then suspending the disk in a bath of pure solvent; the rate of diffusion of the solute from the disk is then ascertained by measuring the apparent weight of the suspended disk a t various times. A list has been published of recent developments (1952) in the physics of rubber (65). TIRES AND TUBES
The new term “abrasion pattern” designates an array of nearly parallel ridges formed a t right angles t o the direction of abrasion on a rubber surface (169). A tire in service has a thin constantly renewed surface layer with a much lower modulus than the layer next beneath it, and the mechanical properties, including abrasion, differ little from those of a pure gum vulcanizate. Studies at the National Bureau of Standards have resulted in a marked improvement in the precision and reliability of measurements of tread wear of commercial tires by using the three following principal elements in the technique: 1. A statistical design of test that will compensate for inequalit of wear on different wheels 2. $he measurement of tread wear by differential weighings 3. The geometric averaging of the rates of wear (174)
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Reliable estimates of tread life can be made from 4000 to 6000 miles of road test with the newly developed techniques. The results of operating conditions, studied by means of a modified Goodyear angle abrasion machine, were compared with actual road teats and showed that the rate of abrasion depends greatly on the severity of the conditions (16). Both the laboratory and road tests show that natural rubber, GR-S-10, and GRS-100 behave similarly n hen the operating conditions are mild but that GR-S-10 and GR-S-100 are much superior to natural rubber when the conditions are severe. By ratings with standard methods in comparing natural and synthetic rubber on ice and snow it was found that natural rubber treads are better than synthetic rubber treads in acceleration, pulling, and stopping; synthetics are better on cornering ability and on wet pavement, but newer polymers are narrowing the gap and show much promise (69). In a discussion on the relationship of tire and car engineering it is stated that tires play an increasingly helpful part in the progress of the American motoring public, not only for durability, but also from the standpoint of greater traction, safety, quietness, ride quality, and car handling characteristics (149). The loss in tire cord strength stems from broken filaments and from a small loss in fiber strength throughout the tire, and studies show that it is not due to abrasion or heat degradation (194). The Goodrich disk-type tester showed the same relative rate of strength loss for rayon and cotton cords as was found in a passenger tire fleet test. Wet twisting with sodium sulfonates of alkylnaphthalenes containing 14 or more alkyl carbon atoms has been found t o increase the breaking strength, without loss in elongation, of tire cord t o almost three times the strength obtained by use of sulfonated alkylnaphthalenes containing 12 or fewer alkyl carbon atoms (5).
COURTESY (IOODVEAR TIRE & RUBBER COS
Laboratory Unit for Dipping Tire Cords in Rubber for Testing Wearing Qualities of Tire Fabrics
COMPOUNDING AND V U L C A N I Z I ~ G
A long series of articles discusses methods employed in compounding research and include descriptions of the synthetic rubbers (48). In Banbury treatment of synthetic elastomers the temperature and thus the amount of breakdown or cross linking can be influenced by properly adjusting the loading, rotor speed, and the time of mastication (146). Since cure time is the sum of the constant vulcanization time and the variable scorch time, it varies with the heat history of the batch, and this may explain many apparently mysterious variations in numerous factory cures (64). Lead, copper, and bismuth oxides, with or without zinc oxide, produce tensile strengths of over 4000 pounds per square inch with natural rubber stocks containing 27.8 volumes (36.1 parts) of coprecipitated oxidized lignin, and the stocks with only zinc oxide did not cure ( 7 2 ) . The authors attribute the difference to the control of the concentration of hydrogen sulfide. Calcium carbonates of particle sizes that range from 0.028 t o 10 microns have been studied and their tests in rubbers reported (186). These “white” carbon blacks are of some interest. A report made on practical compounding for economy illustrates how compound formulas with varying compositions may be developed to meet given specifications, and from these formulas it is possible t o determine the prices of natural and synthetic rubbers a t which the change from one type formula t o another should be made (187). Careful and rather complete results on the vulcanization characteristics of natural rubber indicate that three parameters are necessary t o characterize the vulcanization reaction and that these parameters can be evaluated from strain data (175). Two of them can also be determined from changes in Mooney viscosity a t the temperature of vulcanization.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Homogenization of fillers by mechanical agitation and heating at 150" C. enables them to be incorporated faster and easier (170). When magnesium carbonate is degassed the time of mixing is reduced by one third. During reversion of a vulcanizate the breakdown of cross linkages, including those of polysulfides, predominate over any simultaneous reformation of cross linkages (168). The calculated molar free energy of activation is 33.3 =k 1.7 kcal., irrespective of the temperature, the amount of cure, or the composition of the mix, and this energy is sufficient torupturean4-Sbond. AGING, INCLUDING OZONE CRACKING
A water bomb is being used for studying the oxidation of elastomers with potassium chlorate as the oxidizing agent (67). The method is partial oxidation a t 198" C. Three hours in the water bomb is equivalent to 192 hours in thc oxygen bomb a t 80" C. Analysis depends upon the absorption of ozone of a selected band of visible light a t ozone concentrations in the range 0 to 10 moles % or higher (96). The apparatus is reliable and relatively simple. A dynamic apparatus that provides an effective means for accelerated evaluation of ozonoprotective agents is described (39). I n a comparison of the isotopic method for the direct determination of oxygen in rubber with the Schutze-Unterzaucher method the values obtained by the isotopic method agree very well with the values obtained for the gain in weight upon oxidation, and all are higher than the values obtained by the Schutze-Unterzaucher method, sometimes mare than t e c e (97,98). The latter method may give low oxygen values for compounds that form nonvaport a b l e carbon residues, such as rubber, Crude rubber test specimens for oxygen-absorption measurements are prepared by placing the thin sheet of rubber, of approximately 0.040 inch in thickness, in a folded sheet of 30-mesh stainless steel screen as an envelope (68). In the mechanism of the action of inhibitors of the oxidation of rubber it is stated that since both stable peroxides and peroxidic radicals are present in rubber in the course of its oxidation, a combination of aromatic amino and hydroxy compounds as antioxidants should result in a complete suppression of the oxidation (105). By a study of the oxidation of ruhber films it v a s found that with sulfur the products of oxidation are inactive only at lower temperatures but are definitely active a t 120" C. (106). The consumption of phenyl-,%naphthylamine (PBNA) is slowed down by the presence of sulfur. This antioxidant reacts with peroxidic radicals and forms inactive products over the range 20" to 200" c. The aging behavior of natural rubber in air a t normal storage temperatures will Be better than that predicted by high temperature testing in oxygen, whereas in GR-S stocks the aging behavior in air a t normal storage temperatures will be poorer than would be expected (163). I n accelerated aging tests a - a n d 8-conidendrols were found to be equal or superior to phenyl-0-naphthylamine and other stabilizers (114). More work on the influence of carbon black on the oxidation of natural and synthetic rubbers indicates that the better abrasion resistance of cold GR-S depends on its resistance to high temperature oxidation (7). The tendency of vulcanized rubber containing di-2-naphthylp-phenylenediamine as an antioxidant to turn pink when subjected to light or oxidizing conditions is prevented by adding to the rubber composition a small amount of 2,5-di-te~t-butylhydroquinone prior to vulcanization (165). The appearance of stickiness is not characteristic of an advanced stage of aging but is a type of aging itself (183). A condition especially favorable to softening and stickiness is a slightly elevated temperature and low pressure of oxygen. Vulcanizates having diphenylguanidine as an accelerator had the greatest tendency to become sticky and those with mercaptobenzothiazole the least.
Vol. 45, No. 10
PHYSICAL TESTING
The DeMattia test has been chosen for international standardization, and work is in progress to establish the test conditions for flex-cracking and crack-growth tests (87). Cooperative crackgrowth tests carried out in nine laboratoncs have shown that the agreement between laboratories is poor. The Internatioiial Organization for Standardization (10s)chisel is satisfactory for use with normal rubber compounds but not necessarily for hard compounds above 80" Shore hardness. An apparatus that subjects a rubber test piece to a force in simple shcar, varying sinusoidally with time in the frequency range 0.0017 to 71 cyclesper second has been described (68). The instantaneous values of force and displmemrnt are measured by photoelectric pickups, and, from the display on the screcn of a cathode-lay tube of the mechanical hysteresis loop described b y the vibrating rubber, measurements are madc which make possible calculation of the dynamic shear modulus and hysteresis. There is a great variation in results of tests depending on the size and shape of the spwimen; a rounded-shoulder spccimen should not be used for breaking pure gum vulraniaales because of breakage in the grips of the testing machine (78). At an Armed Forces rubber testing symposium the low temperature tests and apparatus chosen for manufacturers to use included brittleness, hardness, stiffness, and elastic recovery (04). A study is reported of the Goodrich Flexometer with synthetic polymer compounds, since previous tests were all made with natural rubber (107). The reputation of lack of reproducibility should be attributed less to imperfections in the apparatus than to lack of proper care in the adjustment of the equipment and improper preparation of test samples. Special care should be taken to adjust precisely the throw (deflection of the sp0cimens) of the test apparatus. Of subjects discussed a t the 1951 meeting of the International Organization for Standardization particular importance is given to five testing procedures-viz , hardness, tension stress-strain, tear strength, ply adhesion, and abrasion--all of which are described in detail (160). Satisfactory mulls for infrared examinations are obtained b>7 first grinding the gel with an nppiovimateIy equal volunic of sodium chloride until the gel has been disintegrated and each particle coated with salt ciystals (148). Then the h'ujol is gradually worked in and a uniformly dispersed slurry is obtained which is readily mounted 1)etwec.n the sodium chloride plates of the saniplc holder. A new hose testing machine featuring adjr~stabilit~ over :I wide range has been built and described especially for testing automobile radiator hose (153). The %-eather-Ometer has been improved by the addition of eight 20-watt Westinghouse fluorescent pun lamps which provides total ultraviolet distribution more closely remmbling that of sunlight (170). A careful discussion oi the errors of stress-strain testing covered thc history of the test, apparatus, and some present results and their interpretation (20). A rather complete outline and description of methods of control testing in the rubber industry have been published (19). CHEMIC4 L ANALYSIS
A comprehensive review has been given of analytical procedures for 90 important accelerators including 50 citations (as) Silica gel (Celite) allows chromatographic adsorption of S O I ~ P compounds from acetone extracts of vulcanized rubbers yithoiit the destruction of labile compounds, as occurs when alumina columns are used (156). The details are given in a second reference, in which 32 commercial accelerators and antioxidants are studied (156). h rapid sulfur deterniinntlon can be made polarographically on
October 1953
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INDUSTRIAL AND ENGINEERING CHEMISTRY
a vulcanizate sample refluxed and dissolved in pyridine t o which has been added acetic acid, sodium acetate, tylose, and water (148). Sulfate ions can be titrated with barium chloride solution to maximum turbidity with the help of a photoelectric colorimeter, and thus the method is available for the determination of total sulfur in vulcanized compounded rubber (62). For the volumetric determination of persulfate in the presence .of organic substances the iodometric method is most convenient unless the organic substance reduces iodine or oxidizes iodide (99). A simple method that takes only 10 minutes for the determincc tion of acetylenes in specification butadiene consists in filling a sample tube with the gas, flushing it by a stream of nitrogen through a %foot column of alcoholic silver nitrate in an absorber and titrating the liberated nitric acid with standard 0.05 N sodium hydroxide (84). For the routine determination of CC hydro.carbons in furfural or absorber oil, the Cd's are driven through a -short vacuum-jacketed, Raschig ring-packed column and condensed in a graduated pear-shaped centrifuge tube submerged in a dry ice-acetone bath; the volume is obtained after proper corrections are applied (86). The method takes only 15 minutes. As little as 0.02% of ethylacetylene (1-butyne) and vinylacetylene (1-buten-3-yne) can be determined separately and quantitatively in mixtures with other C, hydrocarbons by a relatively simple procedure, which involves precipitation with alcoholic silver nitrate, titration of the liberated nitric acid for total acetylenes, recovery of the acctylenes by treatment with aqueous potassium bromide, followed by bromometric analysis (150). A rapid procedure for the precise determination of ash in GR-S and latices consists of burning the test material in a single sheet of folded ashless filter paper a t 550' f 25' C. (110). The ASTM manganous hydroxide test for oxygen in butadiene vapor has been modified to give reliable results for oxygen concentrations up t o 4.0 volume % (180). Light hydrocarbons in process cooling water and steam condensate are stripped with carbon dioxide and collected in a buret over concentrated potassium hydroxide solution (198). The determination of the isocyanate group in rubber bonding agents is done by treatment with diisobutylamine in chlorobenzene and titration of the excess of amine with hydrogen chloride in chlorobenzene and methanol (196). An ultraviolet spectrophotometric method of determining pfert-butylcatechol consists of weathering the sample of butadiene to dryness, dissolving the residue in distilled water, and measuring the light absorption of the aqueous solution a t a wave length of 279 mH ($8). The fifth annual review of analytical chemistry on natural and synthetic rubbers has been recorded ( 1 4 ) .
e
CARBON BLACK
t
Masterbatches from natural rubber latex and carbon black, prepared by a purely mechanical process and with the aid of a dispersing agent such as Darvan, as already applied to synthetic rubber latices, are satisfactory and offer the usual advantages
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(388). For a study of polar and nonpolar types of rubber loaded with carbon black, two polar elastomers (Perbunan and Hycar OR-25) and one nonpolar elastomer (GR-S) were loaded with SRF black, channel black, and thermal black and vulcanized (41). The carbon black has considerable influence on the dielectric behavior of nonpolar GR-S. Some of the changes of dielectric oharacteristics caused by the carbon black are independent of its type; others depend on type-e.@;., the second zone of dispersion at frequencies less than 10 kc. per sec. appears only with SRF and channel blacks and not with thermal black. The sorption capacities toward GR-S of commercial carbon blacks in decreasing order were Spheron-6, Vulcan-1, Philblack-0, Sterling-105, and Philblack-A (100). High molecular weight srtmples of GR-S are more readily sorbed than low.
2195
A systematic analysis of data in the literature shows that the strain modulus of a vulcanizate can be correlated with the hydrogen and oxygen contents and oil absorption capacity of the carbon black and viscosity of the unvulmnized rubber-carbon black mixture (176). Experiments show that fineness of carbon black-that is, its total surface area-is the dominant factor in the development of carbon-rubber gel and that structure, pH, and &her properties of carbon black play differing but minor rolw (177). The higher the molecular weight and unsaturation of the polymer, the higher is the carbon-rubber gel content, and the effect of unsaturation is great enough to indicate that unsaturation is essential for the full development of the gel. Experimental evidence is offered to show two important facts about carbon black: uniform particle dispersion in rubber does not give the best resistance t o abrasion to a vulcanizate; and hot mixing is very effective in obtaining the best ultimate qualityi.e., toughness, wear, and resilience (22). ADHESION
A panel discussion, followed by questions and answers (166), on automotive adhesives was held a t Detroit. Copolymers of butadiene and 15 to 24y0 of methacrylic acid, prepared in a modified reaction and cured with an organic peroxide, are strong adhesives for attaching rubber to metal (61). Satisfactory bonding between natural rubber and terylene polyester fiber was obtained with polyisocyanate adhesives (123). RECLAIMED RUBBER
The system of making vulcnnized scrap tire rubber with fiberfree rubber for reclaim has been described; the method assures a fiber-free stock by mechanical methods with less elaborate e q u i p ment than for digestive methods ( 4 7 ) . A practical process has been developed for reclaiming ground rubber tire scrap by the use of microorganisms for the removal of cellulosic material (173). Unsterilized ground rubber scrap is wet with dilute inorganic nutrient solutions, inoculated with selected mixed cultures of aerobic, cellulose-decomposing, sulfur-tolerant fungi, and fermented in compost piles until free of cellulose. An article is available on recent developments (1952) in reclaimed rubber (9). APPLICATIONS
I n the present and future requirements of rubberlike materials for a global air force, development is being carried out on fluorinecontaining elastomers, modifications of silicone-base polymers, investigation of polysulfides and acrylates, synthesis of new plasticizers and other compounding ingredients, and fundamental studies of the mechanism of ozone degradation, oxidation, and low temperature failures (11). Airplane tires must withstand high temperatures, perhaps even as high as 500' F.; poly-1,ldihydroperfluorobutyl acrylate (Poly FBA) exhibits sufficiently interesting chemical resistance and physical properties for such use, and in a nonflammable hydraulic fluid, dibromoethylbenzene, exhibits a slight shrinkage only. A general description of the requirements for elastomeric materials for the newer jet bombers and supersonic fighter aircraft has been published (141). Temperature requirements range from -65' t o 600' F., and resistance to swelling in oils and solvents and t o ozone are required. Titles of Air Force contracts and names of some monomers and methods of polymerization being considered are given. The proper selection of transmission belts starts with a determination of the maximum horsepower to be handled by the belt, and this is obtained by multiplying the rated horsepower of the driving unit by a service factor which represents the overload on the drive while starting ( 1 3 7 ) . Tables of the factors are given. Nitrile rubber gaskets give excellent service in electrical e q u i p
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 45, No. 10
The surface coating and impregnation of fabric, including 53 illustrations, the general design considerations and application techniques of many types of coating machines for fabric surface coatings, and saturating systems for fabric impregnation, have been described (111). Reviews are published for recent dcvelopments in footwear--1952, and industrial rubber products-1952 ( 3 3 ) . GENERAL
4 survey has been published consisting of 139 references of contributions in journals and reports on chemical, physical, and engineering subjects (36). The use of GR-S in sponge, tires, COURTESY QOODYEAR T I R E & RUBBER CO. molded goods, footwear, foam, and Playgrounds Surfaced with Pelletized Rubber Protect Children from Injuries extruded goods and the functions of the technical service branch of the ment, showing a n ideal behavior against transformer oil, coolants, Office of Synthetic Rubber were discussed by a panel a t a meeting of the Chicago Rubber Group (197). and water permeability (3). 4 n interesting article describes the mechanical applications of flowed-in gaskets (1.44). A liquid A review has been published of the latest developments in synthetic resin or rubber compound is flowed into the gasket synthetic elastomers during 1951-52 ; it includes a brief discussion channel, and the entire part, with gasket applied, is then baked, and 82 references (57). A very good review has been published and the compound becomes a solid rubbery gasket. of the book entitled “Linear Polymers’’ by Frith and Tuckett Thiokol polymers dispersed in solvents containing other resins (63). give better protective systems than water-dispersed systems, and Laboratory experiments on the use of rubber in bituminous synthetic resin-Thiokol polymer latex dispersion mixtures made pavements show, in general, that the addition of rubber to paving with nonextractable dispersing agents give better protection for mixtures increases elasticity, cohesion, viscosity, and softening steel than Thiokol polymer latices alone (181). point of the bitumen (56). Polybutadienes when hydrogenated to residual unsaturations Ro-search, Inc., is an organization engaged in spreading industrial “know-how” to more than 30 different countries on all of less than 50% produce a class of thermoplastics of outstanding six continents (109). Its approach, scope, and relatively small freeze point, oil resistance, and tensile strength (03). These size are unique. They do no manufacturing but license their hydrogenated polybutadienes are known as Hgdropols. They do not break when struck at - 100’ F. with a hammer, are very hard patents, especially those on footwear. A considerable number of synthetic plasticizers were tested for but not brittle a t temperatures of liquid nitrogen, are useful for their toxicity and skin effects and in most cases were found t o be wire coating, have low resistance to swelling in solvents, have innocuous; a few were irritating, and Paraplex G-25 and Flexol improved ozone resistance, and are vulcanizable. There is a description with photographs of rubber in building 8 x 8 showed severe reactions (116). Carcinogenic material can construction (91). be extracted from commercial carbon blacks as indicated by tests on the skin of Swiss-strain mice. A new portable fuel supply hose, 4 inches in diameter and of synthetic rubber throughout, has been prepared; it weighs less From the pathological standpoint, those dusts containing free than 1 pound per foot and has a bursting pressure of 500 pounds silicate or sericite cause a silicosis, if inhaled in sufficient quantities, provided the size of the mica particles is between 1 and 10 ‘(87). Also freeze-resistant white rubber bands are available for use in packaging foods for storage in refrigerators in temperatures microns (6). The size of the mica particles generally used in dusting rubber is about 312 microns and therefore is not noxious as low as -40’F. Lubricants containing a blend of di-2-ethylhexyl sebacate and aa the causation of pulmonary silicosis. hydrocarbon oils swell rubber less than grease made with the GR-S versus crude natural rubber mas the subject of a symposium sponsored by the Akron Rubber Group, and many ester alone (74). A description is printed of the manufacture and typical cominteresting questions and answers have been published (89, 156). pounding of the four general classifications of rubber hoseDesign principles have been outlined for the use of natural and woven, wrapped, horizontal braided, and vertical braided (71). synthetic rubbers in equipment lining, vibration damping, and Possibilities exist for the use of considerable quantities of corrosion-resistance applications ($3). rubber aboard ships in various decking applications, such as The polysulfide polymer (Thiokol) linings in underground synthetic rubber matting, standing mats, latex-mastic comconcrete storage tanks which are used for the storage of liquid fuels are subject to attack by molds and bacteria under conditions pounds, and seam calking (70). An annotated bibliography on O-rings has been published of tropical temperature and humidity (4). This attack can be inhibited by treating the linings with an appropriate fungicide, (55). For the continuous extrusion and coagulation of latex for the notably pentachlorophenol. Severe biodeterioration was also production of latex thread there is published an illustrated deencountered in the similar linings of tanks that were operated by water displacement systems. scription of the technical aspects, with calculations of extrusion factors, composition of mixtures, changes in volume and in acid An interesting description is given of a new belting plant including its equipment and products made; photographs and a concentration, and maintenance of constant concentration of acid for coagulation (90). flow diagram are included (166). I
October 1953
I N D U S T R I A L A N D E N G I N E E: R I N G C H E M I S T R Y
A review is published of present treatment and improvements in treatment of wastes from synthetic rubber plants since 1946 (151). A bibliography of the action of chemicals on natural and synthetic rubbers has been compiled by the R. T. Vanderbilt Co. and supplemented by Betty Clinebell, librarian of the Division of Rubber Chemistry of the AMERICAN CHEMICAL SOCIETY;the literature of the past 25 years is covered and references to many chemical manufacturer’s and supplier’s bulletins are included (184). The chemicals are grouped in their various general classifications and keyed numerically with the articles or other references in the author-subject index. LITERATURE CITED
(1) Adams, R. J., and Buckler, E. J., Trans. Inst. Rubber I n d . , 29, 17-31 (1953). (2) Aisenberg, I., Nielson, C., and Leonard, F., Rubber A g e (N. Y . ) , 72, 759-61 (1953). (3) Aitchison, T. C.. and Bowers. B. N.. Gen. Elec. Rev.. 55, No. 3. 46-50 (1952). (4) Allen, F. H., and Fore, D., Jr., IND.ENG. CHEM.,45, 374-7 (1953). (5) Ambelang, J. C., Shotton, J. A,, Gottschalk, G. W., Stevens, H. P., and Smith, G. E. P., Jr., Ibid., 45, 204-10 (1953). (6) Ambery, A,, I n d i a Rubber World, 128, 344 (1953). (7) Amerongen, G. J. van, IND.ENG.CHEM.,45, 377-9 (1953). (8) Antlfinger, G. J., and Lufter, C. H., Ibid., 45, 182-6 (1953). (9) Ball, J.,M., I n d i a Rubber World, 128, 201-2 (1953). (10) Banigan, T. F., Jr., IND. ENG.CHEM.,45, 577-81 (1953). (11) Bartholomew, E. R., Rubber A g e (N. Y.), 72, 64-8 (1952). (12) Barton, B. C., and Hart, E. J., IND.ENQ.CHEM.,44, 2444-8 (1952). (13) Beatty, J. R., and Juve, A. E., I n d i a Rubber World, 127, 35762, 423 (1952). (14) Bekkedahl, N., A n a l . Chem., 25, 54-64 (1953). (15) Bestul, A. B., Belcher, H. V., Quinn, F. A., Jr., and Bryant, C. B., J . Phys. Chem., 56, 432-9 (1952). (16) Biard, C. C., and Svetlik, J. F., I n d i a Rubber World, 127, 363-4- (19.521. (17) Bischoff, J., Catsiff, E., and Tobolsky, A. V., J . Am. Chem. SOC., 74,3378-81 (1952). (18) Boggs, F. W., J . Chem. Phus., 20, 632-6 (1952). (19) Boucher, M., et al., Assoc. franp. ing. caoutchouc et inst. frang. caoutchouc, 1949, 2-57. (20) Bowell, S.T., and Rush, I. C., Rubber Age (N. Y . ) ,72,215-19 (1952). (21) Bradford, E. B., J . Applied Phys., 23, 609-12 (1952). (22) Braendle, H. A., Rubber Age ( N . Y . ) , 72, 205-10 (1952). (23) Brazier, S. A., Trans. Am. I n s t . Chem. Engrs., 30, 46-57 (1952). (24) Brooks, R. E., Strain, b. E., and McAlevy, A., I n d i a Rubber World, 127, 791-3 (1953). (25) Brown, R. W., Messer, W. E., and Howland, L. H., IND. ENG. CHEM.,45, 1322-9 (1953). (26) Buhrer, N. E., Rev. q u f m . ind. ( R i o de Janeiro), 20, No. 235, 19-20 (1951). (27) Buist, J. M., Trans. Inst. Rubber Ind., 29, 72-91 (1953). (28) Buist, J. M., and Stafford, R. L., Symposium on Oil Resistance of Rubber, Fdredag Severiges Gummitek. Fdren Hastnote (Swedish Inst. Rubber Technol.). 1952 fin English). (29) Buscar6ns, F., and Capitan, F., Industria putmimica (Buenos A i r e s ) , 14, 18-22, 61-3, 104-7, 109 (1952). (30) Busse, W. F., and Smook, M. A., I n d i a Rubber World, 128; 348-50 (1953). (31) Campbell, A. W., and Tryon, P. F., IND.ENG. CHEM..45. 125-30 (1953). (32) Campbell, G. G., and Tacker. 5.A.. Anal. Chem... 24., 1090-2 (1952). (33) Capen, B. H., I n d i a Rubber World, 128, 199, 201 (1953). (34) Clark, F. E., Banigan, T. F., Jr., Meeks, J. W., and Feustel, I. C., IND. ENG.CHEM.,45, 572-6 (1953). (35) Clinebell, B. J., and Cunningham, E. N., I n d i a Rubber World, 127, 74-8 (1952). (36) Clinebell, B. J., and Straka, L. E., Rubber Age ( N . Y.), 72, 485-92 (1953). (37) Compagnon, P., Rev. g8n. caoutchouc, 29, 478-82 (1952). (38) Compagnon, P., and Liponski, M., Ibid., 29, 272-5 (1952). (39) Creed, K. E., Jr., Hill, R. B., and Breed, J. W., Anal. Chem., 25, 241-4 (1953). (40) Currie, L. L., Ibid., 24, 1327-30 (1952). (41) Dalbert, R., Rev. g8n. caoutchouc, 29, 515-18, 588-92, 649-52 (1952). \----
I
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2197
Decker, G. E., and Roth, F. L., I n d i a Rubber World, 128,33943 (1953). Delattre, R., Rev. g8n. caoutchouc, 29, 278-82 (1952). Dermer, 0. C., and Hawkins, J. J., J. Am. Chem. Soc., 74, 4595-7 (1952). Di Giorgio, P. A,, and Safford, M. M. (to General Electric Co.), U. S. Patent 2,613,199 (Oct. 7, 1952). Dinsmore, R. P., Trans. I n s t . Rubber I n d . , 28, 166-206 (1952); Rubber Chem. Technol., 26, 25-56 (1953). Dorris, T. B., Rubber Age (N. Y.),71, 773-80, 821 (1952). Drogin, I,, I n d i a Rubber World, 127, 365-9 (1952); 127, 50510, 646-50, 797-801 (1953); 128, 59-63, 203-5, 345-7, 350, 353 (1953). (49) Dwyer, 0. E., and Gleich, W. A., Chem. Eng. Progr. Symposium Ser. 48, No. 2, 80-91 (1952). Egloff, G., I n d i a Rubber World, 127, 226-8, 232 (1952). Ericson. H. L., and Carver, L. D., IND. ENG.CHEM.,45,792-5 (1953). Feldon, M., McCann, R. F., and Laundrie, R. W., I n d i a Rubber World, 128, 51-3, 63 (1953). Feldon, M., McKennon, F. L., and Lawrence, R. V., IND. ENG.CHEM.,44, 1662-4 (1952). Filachione, E. M., Fitzpatrick, T. J., Rehberg, C. E., Woodward, C . F., Palm, W. E., and Hansen, J. E., Rubber Age (N. Y.),72, 631-7 (1953). Finigan, C. M., Fullerton, H. V., and Taylor, G. W., IND. ENG. CHEM.,45, 1356-9 (1953). Fisher, H. K., I n d i a Rubber World, 127, 220-2 (1952). Fisher, H. L., Ibid., 127, 641-5, 712 (1953). Fletcher, W. P., itnd Gent, A. N., J . Sci. Instr., 29, 186-8 (1962). \_.__,_
Flory, P. J., Mandelkern, L., Kinsinger, J. B., and Shultz, W. B., J . Am. Chem. SOC.,74, 3364-7 (1952). Foster, F. C., and Binder, J. L., Ibid., 75, 2910-13 (1953). Frank, C. E., Kraus, G., and Haefner. A. J., IND. ENG.CHEM., 44, 1600-3 (1952). Prey, H., A n a l . Chim. Acta, 6 , 28-30 (1952). Frith, E. M., and Tuokett, R. F., J. Am. Chem. Soc., 75, 2535 (1953). Garvey, B. S.,Jr., Yochum, D. W., and Morschauser, C. A., Rubber A g e (N. Y . ) , 73, 361-8 (1953). Gehman, S.D., I n d i a Rubber World, 128, 199-201 (1953). Gilbert, R. D., and Williams, H. L.. J . Am. Chem. SOC.,74, 4114-18 (1952). Gillman, H: H., and Hames, W. M., Jr., Rubber Age ( N . Y . ) , 71, 767-71 (1952). Gowanq, W. J., A n a l . Chem., 24, 1648-9 (1952). Grace, N. S., and Winter, G., I n d i a Rubber World, 126, 633-5 (1952). Greenleaf, E. F., Rubber A g e (N. Y . ) ,71,495-9 (1952). Gregory, F. S., I n d i a Rubber World, 127, 223-5 (1952). Griffith, T. R., and Mac Gregor, D. W., IND.ENG.CHEM., 45, 380-6 (1953). Grummitt, O., and Splitter, J., J . Am. Chem. SOC.,74, 3924-9 (1952). Harper, R. M., Rubber Age ( N . Y . ) ,73, 355-8 (1953). Havenhill, R. S., Carlson, L. E., Emery, H. F., and Rankin, J. J., IND. ENG.CHEM,,45, 1128-33 (1953). Heinisch, K. F., and Bie, G. J. van der, Arch. Rubbercultuur ned-India, 28, 1-60 (1951); Mededeel. Indones. I n s t . Rubberonderzoek, No. 84, 60 pp. (1951); I n d i a Rubber World, 127, 503-4 (1953). (77) Helin, A. F., Gyenge, J. M., Beadell, D. A., Boyd, J. H., Mayhew, R. L., and Hyatt, R. C., IND.ENQ.CHEM.,45. 1330-6 (1953). Herzog, R., and Burton, R. H., Schweiz. Arch. angew, Wk.U . Tech., 18, 177-89 (1952). Hillyer, J. C., and Smith, J. V., Jr., IND.ENO.CHEW.,45. 1133-6 (1953). Houwink, R., Rev. g8n. caoutchouc, 29, 346-53 (1952). Houwink, R., de Vries, A. J., and van’t Wout, J. W. F., Ibid., 30, 181-5 (1953); G u m m i u. Asbest, 6 , 104, 106-7 (1953). Howland, L. H., Neklutin, V. C., Provost, R. L., and Mauger, F. A., IND. ENQ.CHEM.,45, 1304-11 (1953). Howland, L. H., Reynolds, J. A,, and Provost, R. L., Ibid., 45, 1053-9 (1953). Hyzer, R. E., A n a l . Chem., 24, 1092-3 (1952). Ibid., pp. 1093-4. Iknayan, A. N., I n d i a Rubber World, 126, 505-7 (1952). I n d i a Rubber World, 126, 530 (1952). Ibid., 127, 640, 712 (1953). Ibid., 128, 75-9 (1953). James, R. G., Rubber A g e and Synthetics, 33, 167-9 (1952). Jones, F. E., Rubber Developments, 5, 83-90 (1952). Jones, H. C., and Klaman, C. A., Rubber Age ( N . Y.1, 73, 63-70 (1953).
2198
INDUSTRIAL AND ENGINEERING CHEMISTRY
(93) Jones, R. V., Moberly, C. W., and Reynolds, W. B., IND. ENG.CHEM.,45, 1117-22 (1953). (94) Kahn, I., I n d i a Rubber WorEd, 126, 500, 507 (1952). (95) Keen, W. N., Ibid., 128, 351-3 (1953). (96) Kiffer, A. D., and Dowell, L. G., A n a l . Chent., 24, 1796-8 (1952). (97) Kirshenbrsum, A. D., and Streng, A. G., Ibid., 25, 638-40 (1953). (98) Kirshenbaum, A. D., Streng, A. G., and Nellen, A. H., Rubber Age ( N . Y.), 72, 625-30 (1953). (99) Kolthoff, I. M., and Carr, E. M., A n a l . C'hem., 25, 298-306 (1953). (100) Kolthoff, I. M., and Gutmacher, R. G., J . Phys. Chein., 56, 740-5 (1952). (101) Kolthoff, I. M., and Meehan, E. J.. J. Polvmer Sci.. 9, 43352 (1952). (102) Kolthoff, I. M., Meehan, E. J., and Carr, E. RI., J . Am. Chena. Soc., 75, 1439-41 (1953). (103) Kolthoff, I . M., and Miller, I. K., Ibid., 74, 4419-22 (1952). (104) Kurtz, S. S., Jr., and Martin, C. C., I n d i a Rubber World, 126, 495-9 (1952). (105) Kuz'minskii, A. S., and Angert, L. G., Doklady Akad. N a d i S.S.S.R., 82, 747-50 (1952). (106) Kuz'minshi, A. S., and Leshnew, N. N., Ibid., 83, 111-14 (1952). (107) Labbe, B. G., I n d i a Rubber World, 128, 193-8 (1953). (108) Lepetit, F., Reo. g i n . caoutchouc, 30, 256-61 (1953). (109) Leslie, L., I n d i a Rubber World, 126, 773-6 (1952). (110) Linnig, F.J., Milliken, L. T., and Cohen, IZ. I., J . Research iVatl. B u r . Standards, 47, 135-8 (1951). (111) Litaier, C. A., Rubber Age ( N . Y.), 71, 501-6, 631-8, 781-6 (1952). (112) McDonald, H. A., Administrator, Reconstruction Finance Corp., March 1, 1953. (113) Macey, J. H. (to B. F. Goodrich Co.). .:1 S. Patent 2.567.741 (May 20, 1952). (114) Mack, C. H., and Bickford, W. G., J . Am. Oil Chcniists' Soc.. 29, 425-30 (1952). (115) Madge, E. W., Trans. I n s t . Rubber Ind., 28, 207-23 (1952). (116) Mallette, F. S., and Von Haam, E., Brch. l n d . Wyg. and Occupational Med., 6, 23142 (1952). (117) Maron, S. H., Moore, C., and Powell, A. S., J. Applied Phys., 23, 900-5 (1952). (118) Marvel. C. S.,Menikheim, 5'. C., Inskip, H. K., Taft, 'AT. K . , and Labbe, B. G., .I. Polymer Sei., 10, 39-48 (1953). (119) Marvel, C. S., Pet-rsnn, 1%'.R., Inskip, H. K., RlcCorkle, ,J. E.. Taft, W. K., a n d Labbe, B. G., IxD.~ExG. CEEM., 45, 1532-8 (1953). Marvel, C . 9.. Weil, E. D., Wakefield. L. B.. and Fairbanks. C. W., J. Am. Chenk. Sx.,75, 2326-30 (1953). Massa, A. P., Colon, H., and Schuiig, W. F., IND.E w . CHEX..45. 775-82 11953). Messenger, T . H., and Graham, P. C. C., R7rhber Deilelopnients, 6, NO. 1, 2-10 (1953). Meyrick, T. J., and Watts, J. T., India-Rubber J.. 122, 467-8 505-6 (1952). Miller, E. C., Crawford, F. W., and Simmons, B. J.. Anol. Chem., 24, 1087-90 (1952). Montu, M., Rev. gSn. caoutchouc, 29, 506-10 (1952). 71,025-8 Morris, R. E., and James, R. It.,Rubber Age (N. Y.), (1952). Morton, A. A., Rubber Age (iV. Y . ) , 72, 473-6 (1953). Morton, A. A., Bolton, F. E., Collins, F. W., and Cluff, E. F., IND. ESG. CHEM.,44, 2576-82 (1952). IMorton, A. A,, and Cluff, E. F., J . Am. Chem. SOC.,74, 4056-9 (1952). Miiller, E., Bayer, O., Petersen, S., Piepenbrink, H. F., Schmidt, F., and Weinbrenner, E., Angew. Chem., 64, 52331 (1952). Nelson, R. A., Jessup, R. S., and Roberts, D. E., J . Research Natl. B u r . Standards, 48, 275-80 (1952). Newton, R. G., Rubber Developments, 5, No. 2, 49-56 (1952). Nolle, A. W., and Mifsud, J. F., J . A p p l . Phys., 24, 5-14 (1953). Paley, W. S., India Rubber World, 126, 501-4 (1952). Parker, C. A,, Nature, 170, 53940 (1952). Parker, C. A., and Berriman, J. M., Trans. I n s t . Rubbe/- I n d . , 28,27%-96 (1952). Perry, N., Rubber Age (N.Y , ) ,71, 629-30 (1952). Pollack, M. A,, I n d i a Rubber World, 127, 497-502, 810 (1953). Polmanteer, K. E., Servais, P.C., and KonMe, G. M., IND ENG.CHEM.,44, 1576-81 (1952). Popper, F., Rubber Age ( N . Y.), 73, 81-3 (1953). Postelnek, W., Chem. Eng. News, 31, 1958-60 (1953). Proske, G. E., Kautschuk u. Gummi, 1, 339-43 (1948); Chem. Zentr. (Russian Zone Ed.), 1949, I, p. 1428.
Vol. 45, No. 10
(143) Pryor, B. C., Harrington, E. W., and Drueaedow, D., IND. ENG.CHEM.,45, 1311-15 (1953). (144) Rand, W. M., Jr., Rubber A g e ( N . Y.), 72, 477-81 (1953). (145) Reich, M. H., Schneider, R. E., and Taft, W. K., IND. ENG. CHEM.,44, 2914-22 (1952). (146) Reich, M. H., and Taft, W. K., R u b b w Age (N. Y.1, 72,619-24 (1953). (147) Reinisch, L., Rea. g i n . caoutchouc, 29, 593 (1952). (148) Rippere, R. E., A n a l . Chem., 25, 363 (1953). (149) Roberts. E. A.. I n d i a Rubber World. 126. 767-71 (1952). (150) Robey, R. F., 'Hudson, B. E., Jr.,'and .Wiese, H. K.,' A n a l . Chem., 24, 1080-2 (1952). (151) Rostenbach, R. E., Sewage and I d . Wastes, 24, 1138-48 (1952). (152) Rubber A g e ( N . Y.), 71, 639 (1952). (153) Ibid., 72, 69-70 (1952). (154) Ibid., 72, 624 (1953). (156) Ibid., 73, 73-80 (1953). (156) Ibid., 73, 209-10 (1953). (157) Ibid., 73, 388 (1953). (158) Rubbex Research Inst. Malaya, Circ. 35 (1952). (159) Schallamach, -4., Trans. I n s t . Rubber I d . , 28, 256-68 (1952). (160) Scott, J. R., Ibid., 28, 249-55 (1952). (161) Seeger, N. V., AIaslm, T. G., Fauser, E. E., Farson, F. S., and Sinclair, E. A , , I n d i a Rubber World, 128, 216 (1953) [Rnbhci,Age (AV,Y.), 73, 216 (1953)f. (162) Shankar, U., J . S a . I n d . Reswrclt [Jptdtb), 10B, 263-9 (1951). (103) Shelton, J. R., and Cox, W.L.,TND,
[email protected].,45, 392-401 (1953). (164) Slabey, V. A., J . Am. C'hem. Soc., 74, 4930-2 (1952). (165) Slovln, D. G. (to United States Rubber Co.), U. S . Patent 2,610,983 (Sept. 16, 1952). (166) Smith, W. L., I n d i a Rubber Wovld, 126, 641-4 (1952). (167) Gmook, AI. A., Roche, I. D., Clark, W. B., and Youngquist, 0. G., I n d i a Rubber World, 128, 54-8 (1953). (168) Snyder, H. R., and Hallada, D. P,, J . Am. Chem. SOC.,74, 5595-7 (1952). (169) Spencer, W.B., Jr., Davis, K. R., Kilbouine, F. I,., Jr., and Montermoso, J. C., IWD.ENG.CHEST.,45, 1297-304 (1953). (170) Stalinsky, E., Rev.g S n . caoutchouc, 29, 510-4 (1952). (171) Stambaugh, R. B., IXD. Evo. CHEV.,44, 1590-4 (1952). (172) Stewart, R. A., and Williams, PI. I,., Ibid., 45, 173-82 (1953). (173) Stemart, W. D., Cramfold, I
