refractories - ACS Publications

INDUSTRIAL AND ENGINEERING CHEMISTRY

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(86) Schoenfeld, F. K., Trans. Am. Jnst. Chem. Engrs., 35, 447

(1939). (87) Servais, P. C., Rubber Age, 58, 579 (Feb. 1946). (88) Shackleton, J. W., Modern Plastics, 21, 99 (Feb. 1944).

(89) Shine, w. Ma, “Modern Plastics Enwclopedia,” P. 201, New York, Plastics Catalogue Corp., 1946. (90) Stanton, G. W., and Henson, W. A., Modern Packaging, 19, 194 (Mar. 1946).

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(91) Strain, F., Xodern Plastics, 21, 97 (Aug. 1944). (92) Straka, C. J., Ibid., 20, 80 (July 1943). (93) Tompkins, H. W., Aero Digest, 46, 109 (July 15. 1944). (94) Wakeman, R. L.,Modern Plastics, 18, 65 (July 1941). (95) Williams, D. R., Chem. & Met. Eng., 52, 112 (Nov. 1945). (96) Young, D. W., and Harney, W. C., IND.ENQ.Cmhf., 37, 675

(1945).

REFRACTORIES RAYMOND E. BIRCH, Harbison-Walker Refractories Company, Pittsburgh, Pa.

N

OTWITHSTANDING the restrictions on new production facilities, some new refractories made their appearance during the war. Their use is now becoming more widespread, although readjustment is slow since the industry is still under great pressure for high production. Refractories are a large tonnage product, and the bulk of he tonnage is represented by products made of fire clay. This group of products represents in volume approximately 75% of all refractories (60y0of the total value), the remainder on a tonnage basis being silica refractories (about 20%), and the small but vitally important group comprising magnesia, chrome, graphitr, carbon, silicon carbide, forsterite, and many others. I n fields apart from heavy tonnage refractories, in the realm of the expensive and highly pure oxides, important developments are taking place. Refractories are being called upon to perform tasks which were formerly outside of their scope. The nature of the role performed by refractories in wartime atomic research has not been disclosed, but this subject is still active. I n the border zone between porcelains and refractories, an extensive program is being directed toward the development of ceramic parts for gas turbines, to gain the advantage of greater efficiency through operation a t temperatures beyond the range of metals. The age of pure oxides in the refractories field, long heralded, seems to be beginning a t last. Because refractories is an industry basic to almost all other industries, it must follow the course of industry; the accelerated industrialization of the Southwest and West has led to expanded facilities for refractories manufacture in those sections. FIRE-CLAY REFRACTORIES

Fire-clay refractories are classified primarily by pyrometric cone equivalent (P.C.E. or fusion temperature) but also with consideration of volume stability at high temperatures and resistance to thermal shock. The most refractory type is the superduty fire-clay brick comprised mainly either of pure flint clays or kaolin. To earn this classification these refractories shoJv a combination of high refractoriness, volume stability, and spalling resistance, which was unthought of prior to the advent of the superduty product in the early thirties. I n almost every industry, plant operators have learned that the life of certain furnaces is amply lengthened to warrant the slightly greater expense involved in using superduty fire-clay refractories, especially since labor costs and freight charges are the same. This product has had a profound effect in reshaping the outlines of the refractories industry, Its demand for controlled quality has intensified prospecting for the purest clays and has modified the character of quality control programs. I n the class of superduty fire-clay refractories is a product of extra high firing (2650’ to 2800’ F. us. the normal 2300’ to 2500’ F.), which has advantages including the fixation of its iron oxide impurities so that they will not catalyze the breakdown of carbon monoxide to carbon dioxide and

carbon. Where this reaction occurs in high concentrations of the monoxide, as in iron blast furnaces and various furnaces in the oil and chemical industries, carbon forms within the pores of the refractory in a graphitized form, the growth of which will disrupt the brick. High fired refractories of all types also tend to havr greater stability under load a t high temperatures. The next step below superduty brick, in descending the scale of refractoriness, is represented by the high heat duty refractories, which still amply fulfill the requirements of the vast majority of applications and actually prove better than superduty brick for many services. There are some services where even less refrac*tory types may be used. It is particularly true of fire-clay refractories that many important properties may be controlled by modifying composition and process. Thus, vast leeway is possible to meet particular conditions encountered in individual types of furnaces. The latest development in the construction of vertical cylirldricsl acid towers and tanks is shown in Figure 1. The novel feature is the use of universal circle acidproof brick, which are so designed that a single shape will turn almost any circle. Brick of similar design are also used in domestic furnaces and in grai iron cupolas. HIGH ALUMINA REFRACTORIES

I n the system alumina-silica, refractoriness increases directly with alumina content (except for compositions with less than 5.5% alumina), and it is therefore logical to proceed from fireclay refractories (alumina contents of 20 to 43%) to the high alumina products, in building furnace structures which will withstand higher temperature. The principal base material is most frequently a hard Missouri diaspore mined Kith its associated clay matrix so as to yield a raw material analyzing above 70% .41,0,, calcined basis. Blends of this material with clay or n i t h pure aluminum oxide yield the standard classes of high alumina refractories with alumina contents of 50, 60, 70, 80, and 90% A1203. During the \Tar the latter product became established for aluminum melting furnaces, for high temperature ceramic kilns, and for many other uses. This application for alumina was considered important enough to allow its diversion from supplies which otherwise could have been used in making metal. Brick analyzing 90% alumina have been marketed for years but are now stirring renewed interest because of their improved characteristics. Refractories with an alumina content of 99% are also available, and some are being fired to approximately 3200‘ F. High alumina refractories containing diaspore have long utilized this constituent in the form of dense material previously calcined to remove shrinkage. A recent development is the introduction of rotary kilns for this calcination, which replaces the prior practice in which crude shapes or dobies were fired in periodic kilns to temperatures which were necessarily lower. Rotary kiln calcination gives a more dense refractory grain. ID

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corisuquence the fired refractory made from these grains has lower porosity. A widely used 7OCL A 1 2 0 3 refractory now typically has a porosity of 24 to 267,, as compared to the 30 to 35% porosity for earlier brick of this type. Rotary kiln calcining has supplied the latest step of progress This improvement is particularly important for the use of these refractories in rotary kilns for burning portland cement, lime, and dolomite, where decreased porosity gives demonstrated extension of service life. 9 comparatively unheralded accomplishment is the development of high alumina brick in the 50, 60, and 90y0 A1*O3gradeq which equal the spalling resistance of superduty fire-clay brick. The so-called sillimanite refractories usually made from Indian kyanite (two minerals of the same composition: A1201.Si02)are well known for their combination of excellent properties which hm given them wide usage, especially in the glass industry. Kews from India (28) is highly discouraging for a continuance of shipments of kyanite in ample supply for established needs. Faced with a similar situation during the war, Germany produced a substitute material by high temperature reaction of bauxite and kaolin (36), but this introduces complexities. American kyanite does not burn to the high density of grain (34) characteristic of Indian kyanite, and the use of topaz is retarded by the difficulty of coping with the fluorine released when it is calcined (SO). The market for kyanite refractories was closely scrutinized during the war, since high priority for shipping from India was required (24). An unsuccessful attempt to use them in an open heartb roof replacing silica refractories was recorded (15). SILICA REFRACTORIES

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the silica roof is the factor in open hearth operation which sets the maximum temperature and limits the speed of steelmaking. Study of this problem led to the development of a new silica refractory, referred to as superduty, based on the use of pure washed quartzite in which the total content of alumina, titania, and alkalies does not exceed 0.5%. This degree of suppression of impurities, previously believed unnecessary, has given a product which has withstood a 25 pound-per-square-inch load t o 1705' C. (3100" F.), a close approach to the ultimate which can ever be achieved with silica refractories. The product is well established in glass tanks and open-hearth furnaces; in the latter a 20% increase in life is not unusual. Close correlation of open hearth roof life with alumina content has been reported by Kraner ( 2 6 ) , rTho has pioneered in bringing a realization of the importance of lovi alumina in silica refractories. Data on the melting characteristics, which explain the succes3 of the superduty silica brick, are given in Figure 2. The average silica brick develops 30% of liquid a t 2990" I?,, whereas the superduty product does not reach this stage of melting until a temperature of 3090" F. is reached-a full 100' F. higher. A series of papers by Harvey and others (28) has apparently established to the satisfaction of everyone that the brown-to-red blotches, or "liver spots," on silica refractories have nothing to do with quality, except for their tendency to suggest high purity. Silica refractories are now being analyzed quantitatively for alumina by spectrographic methods. Quarry-site washing plants, a new development in the industry, are on the drawing boards. Thus, especially in silica refractories, the emphasis is on increased purity. Effective dust control methods are practiced in the silica brick plants, and in the United States a plant-site unit for aluminum therapy was first>used in this industry.

Silica refractories are made by bonding pure quartzite with hydrated lime and then firing to about 2625' F. to produce substantial conversion to cristobalite and tridymite. While silica brick generally sell for the same base price as high heat duty h e MAGNESITE AND CHROME (BASIC) REFRACTORIES clay refractories, they are 30 remarkably well adapted to certain services that their worth bears little relation to their cost. I t is Magnesite and chrome were for a long time thought to be fully unlikely that any other refractory exists, a t any price, which competitive as refractory materials, but about fifteen years ago could serve so well in those services where silica brick are best it was found that, for most services, blends of the two materials known, including the by-product coke oven, the glass tank, and gave better refractories than did either alone. Together the chrome-magnesite refractories are widely extending their markets the basic open-hearth steel furnace. I n the sprung arch roofs of the two latter furnaces, silica refractories are necessarily standard as a result of very fruitful technical improvements. practice because of their ability to carry loads to temperatures of Refractory or dead-burned magnesite is so called because it was 3000' F. or higher. formerly produced exclusively by sintering the magnesia proThe silica refractories industry is still snowed under with orders. duced from the natural mineral magnesite. This name persists To the normal maintenance requirements of industry has been even though the refractory magnesia is now produced to a conadded the imminent need for rebuilding hundreds of coke ovens. siderable extent by dead-burning magnesium hydrate precipiIt has been estimated that 2400 by-product ovens are nearing the tated from sea water, bitterns, and inland brines, and also from twenty-year age limit, which is the nominal age a t which repair brucite (I?'). costs and technological advance unite t o urge replacement. Since chrome ore is of igneous origin and the magnesite is The melting point of SiOl is 1728" C. (3142" F.), and for years clinkered by high temperature firing in a rotary kiln, it might seem there had been great needless to apply high satisfaction with the temperatures when fact that lime-bonded h i n g brick made of silica r e f r a c t o r i e s their blends. Actuwere usable under ally more than half l o a d t o 1 6 5 0 " CJ of these basic refrac13002' F.), an aptories utilize chemical proach to the ultibonds which develop mate melting point in drying the brick, unequaled in any 30 that firing is unother commercial renecessary. However, fractory. I n a n y a large tonnage of o t h e r temperature chrome-magnesite rerange this margin of fractories (approxi78" C. would have mately 80% chrome been of little conseore blended with quence, but to the 20y0 magnesite) is steelmaker it is vital, fired to 3000" F. or since the melting of Figure 1. Universal Circle Brick for Vertical Acid Tanks higher.


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The tuiiriel kilns in which thebe refractories are fired may operate for several years without a shutdown and thus present severe service conditions for the refractories of which they are built. Sprung arch construction in the firing zone has been used to date, although suspended arch construction is now to be tried. Thereas only high fired forsterite or chrome-magnesite refractories have previously been used in this sprung arch construction for 3000" F. service, the largest of the new kilnfunder cnnstrirc%tiori

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MgO) or more doloniitic in cvnipusition. An analysis ot quebtionnaire replies concerning preferred open-hearth constructior was supplied hv Dehenham (11). FOKYTERII'E

The mobt p i o g r e ~ b i ~step e of the la3t two decades in basic it'Irartories n a s the discovery that chrome and magnesite refractories would sustain loading to much higher temperature. if the ever-present silicate impurities were mnverted t c t iorsterite (2lIgO.SiO?),the niost refractorv of the magnc &mi silicates. This development extended the use of basir refractories from the hearth of high temperature furnace? to their side walls and crowns. Following these surcestit was natural that a new refractory would appear consistingalmost entirely of forsterite (19). I t has found many us+ of which one of the most impor'ant, classifiable as a NH' development, is in the glass industry. Forsterite refractorirs are now extensively used as glass tank checkers, anr, tor the walls and arches of the regenerative chamber ~ ~ Their reaction a i t h alkalies iq a dry one in which t h dr, not hecome glazed or fluxed. DV LVMITE

C. 1200 F. 2192

1300

1400

2372

2552

Figure 2.

1500 27'32

1600

2912

1700 3092

Melting Rehavior of Silica Refractoriel.

tiunb uf supeidutj silica brick and of a aluiiiiiitt product. Thus the refractories industry is providing its on n proving ground. I n a complete new refractories plant for nianufacturing basic brick, the raw materials mi11 be screened to various grain sizes to allow recombination to give close control of sizing and attainment of high density in the pressed brick. The art of metal-casing magnesite refractories continues to shorn progress. From MacCallum's discovery twenty-five years ago that magnesite grain4 rammed into steel tubes would fusc together in a furnace nall to give a monolithic heat-bonding structure, many variations ha>e been developed. The careful sizing of the brick mix and high pressure forming have contributed greatly to the improvement of this type of product. Plastic chrome ore rammed into place is used in the steel industry, particularly in heating furnace bottoms, and in the paper industry for packing the nalls and bottoms of sulfate recovery boiler units. Chemically bonded chrome brick have shown improved results in the bottoms of a number of these furnaces. The open-hearth steel furnace bottom, u hich traditionally was burned in by fusing inch after inch of magnesite grains, has swung in large part t o rammed basic bottoms containing a cold setting agent, such as sodium silicate. K i t h such a grain material, rammed with pneumatic rams, it has proved possible t o install a densely packed bottom and to produce steel many hours before the old practice would have allowed it. A good case can still be made for the traditional burned in bottom, particularly if a well giaded sizing of grains is used, and many operators prefer it. The basic ramming mixci may be of the high magnesia type (ahnut 8 0 5

( M y in the steel industry is dolomite an importunt I ( rractory, but there it is vital. A million and a quarter toriare used annually in the United States (%), primarily for maintaining the hearth in the basic open hearth furria~i \I hereas in this country refractory dolomite is fired II ~ o t a r ykilns, British practice is to ube shaft kilns to whirk both coke and lump dolomite are charged. The hi\t inierican plant utilizing the British process was recent11 installed by Dolomite Refractories Ltd. a t Dundas nral Hamilton, Ontario. The lime in such products, R hether burned in shaft or rotary kilns, is sufficiently stabilizec against hydration and recarhonation only for the interidec service. However, the permanent stabilization of dolomite d century-old problem, has been accomplished by addirig enough silica to convert, a t high temperature, all o' the lime to refractory compounds consisting chiefl? oi cither the orthosilicate (2CaO.SiOi) or the trisilirstt \3CaC).Si02). Dolomite grain, so stabilized, is now manufacturecl in England (39) and made into brick by a number of companieit served usefully during the Rar in England when sea water maynesite wab inadequate to whollv replace the dead-burned mayn 4 1 e forinrrly ohtained abroad. SILICV% CARBIDE

Silicoii carbide roller hearths for steel heating furnaces havt been described (37). Although they \Tere not a war-born drvelopment. the use of silicon carbide skid rails was given impetu. in replacing both uncooled alloy skids and tvater-cooled pipL Another interesting development is the use of silicon carbidc checkers in regenerators for making oil gas arid for the cracking o' hydrocrtrhnns. CARBO3 4 N D GRAPHITE

Graphrtt crucibles, retorts, m d stoppers for steel ladles supplied a greatly increased demand during the war in the face 0' aggravated supply problems. Carbon refractories are experiencing a postwar boom associated with many trials in blast furnace bottoms and hearths. They have been extensively used i r l blast furnace linings on the continent. ZIRCO3

The uw of Arconia is largely confilled to laboratory wait w h m w s w m e tonnagr markrtcl have hccn tirvrliped for t ' i ~ l l -

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sized brick made of zircon, the silicate. Applications include the aluminum melting furnace, where it is considered that this refractory as well as 90% alumina brick is resistant to wetting by the metal. Studies of thermal length change of zirconia were recently reported by Geller and Tavorsky (16). SPECIAL REFR4CTORIES

The d i p caating of clay pots for optical glazs riianufactuie at the Sational Bureau of Standards R as recently described (21j . Flux blocks for the hearths and loner side Ti-allq of glass tanks torni the principal market for slip ca>t refractories. Thia i q also rlie major market for fusion caat ware produced by fusing pure materials and casting them into molds to crystallize upon cooling. Primarily introduced as fused mullite refractories, these products may now contain zirconia or, i n some caqes, may consist moat largely of alumina. Electrically fused forsterite ha. been studied h\- the Biiremi of Mines a t Yorrir. Tenn. (231. PURE OXIDES G a i rulbiue research, a ne\\ arniospheric nitiuyrn pocca3, ana hangeb in glass technology ale R few of the reasons why there is a: present a great interest in pure oxide refractories. h recent .tudy (6) showed t h a t there are almost a -core of chemical elementa yielding compounds not melting belo\+ 1800' C. Only ten have compounds a t present produced in such abundance as to Zuggest t h a t brick could be made in large quantity, regardlesq of cost, assuming t h a t all technical problems could be solved. Thew tire the oxides of magnesium, aluminum, zinc, titaniuni,zircwnium, iiariuni, strontium, calcium, chromium, and nickel. When variIUS 3f these are dismissed because of stability limitations or over\\ helming econoniic considerations, the most promising refractor) materials for use a t highest temperatures are found to be magnesia (melting point 2800" C., 5070" F.), alumina (2030" C., 3720" F.) and zircon (2430" C., 4410" Fa). Except lor compounds of these three elements (and of carbon) there are no other stable I vfractory substances which would have a raw material cost (under $3.00 per 9-inch brick and a melting point above 2000" C. Each is available in a high degree of purity. l l u m i n a and magnesia resist a greater variety of slags than zircon, 15 hich is an acid refractory. Both are now extensively used as refractorie? and are iiwtined t o become even more important. For laboratory itare and for certain wartime i i w a cuat i. le32 important, and oi her oxides may be conaidered. One manufacturer lists beryllia and thoria tubes, and it has been stated (10 that tubes of the latter can be made ga-tight a t 2200" C. I n a private communication F. H. Norton of the Massachusetts Institute of Technology reported t h a t beryllia may produce a respiraCory tract disease similar t o silicosis, and that it is good practice to provide for thorough ventilation of furnaces and crushing and grinding equipment from which dust or fume may arise. The aeronautical companies represent a segment of indu.;tij now receiving initial introduction to the refractories field, through the atudy of refractories for coating exhaust tubes of jet-propelled engines and for construction of turbine parts. The German techarid ceramic turbine nicians had worked on this problem (35), blades might have been a reality had the research had a higher priority. Military research on this subject now engages a majoi part of the refractories reseaich facilitier of Unitrd Stater univer-ities and research institutes. When it is realized that marly factora are still unknown about the commonest types of refractories, it is evident that work n i t h pure oxides is in its infancy. Melting point data mark only the beginning in the search for knowledge. Thermal expansion, volatility, reduceability, reaction with gases, strength, and allotrophy are only a fev of the fartnr- which may govern servire pwformanrr. I

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INSULATING FIREBRICK

Since the int roduction of insulating firebrick for direct C X ~ J U sure to furnace atmospheres, their use has spread widely. Staiiliardized classes include types for service a t 1600°, 2000°, 2300' and 2600" F., and products are available which do not show higk shrinkage even a t 2800" F. The principal advantages of theat lightn eight refractories are (a,fuel economy through reducer r capacit? heat losses, ( b j quicker heating up time due to l o ~ e heat of the furnare, (c'i greater fleuibility in application resulting from, decreased meight, and (d economy of spar(' hecaurc of highe. insulating etficiency. CASTABLES, CEMEhTS, AhD PL4STICS

Kelractoriea niay be purchared as castables or refractory cui,. crete comprising a refractory aggregate and a cement, u-unllj I) the calcium aluminate type. Progress in this art is eviden((d IJ: the recent standardization by the American Society for Testing Material of grades for 2400 O F. and 2700' F. service, and by the Fact that the United States Kavy has recently established a specification ( 8 ) for a so-called 3000" F. service alumina-silica caatable. One such product is reported to show negligible shrinkage when heated at 3000" F. for 5 hours. Lea ( 2 7 ) has shown thar both calcium monoaluminate and high alumina cements show decrease in set strength nhen cured a t 45" C. as compared wit1 18" C. >\loser (SI)has survpved the entire topic of refractor! concrete. Progress has similarly been made in pla >hipped in moisture-retaining packages so as to be read) for uatThe United States Navy has used large quantities of a superdut: plastic a hich hay high spalling resistance and withitande a pane refractoiinezs test a t 3000" F. Mortars for laying refractor) brick are obtainable made irun alniost every available refractory material, but four types wil, rove1 almost all uses. These are mortars whose base is fire clay high alumina materials (above 50% + 1 1 2 0 3 ) , chrome ore, or silica Heindl and Pendergast (20)have studied the field extensively The cost of the mortar may represent a large part of the cost oi construction, and this is eqpecially true of acidprcof constructior where the mol tar cost may exceed by several times the investment in the brick. Since the joints are also the more vulnerable to attack, these factors argue strongly for the. use of larger hrirk sizes ro ac: to Ieduce the ioint area. FCRNACE CONSTRUCTION AND MAlNTENAhCL

In furnaces 1% here refractory life is >hart and a ahutdonn throM +\pensive equipment into idleness, there is a market for specia refractories which may strengthen the weakest spots. Boggs ( 7 ) has given a n example of a copper reverberatory smelting furnace designed for smelting 500 tons daily, now smelting 2260 tons, as a result of modifying the trpea of refractorie? used 2nd changing I he construction. Refractory sprung arches were studied by McDowell (2Q), aric .here have been a number of studies of the specific problem of replacing silica refractories by basic refractories (magnesite, chrome Eorsteritej in the open hearth roof. For a eprungarch roof of suck d periodically charged furnace it i4 now realized that silica refractories have the ideal and unique characteristic of essentially a zero coefficient of thermal expansion from about 1200" to 2800" F Thus the arch may not riae and fall appreciably during tapping and charging. Basic refractories continue to expand with temperature rise and to contract upon cooling. T o overcome thi? disadvantage, the brick may either besuspendedindividually or i r g r o u p (instead of sprung fiom .sal1 to wall), or a rotating skewback niay be provided. The advantage of operating the open. hearth furnace a t temperatures above the melting point of ailicb refrartoriw is appealing, and current trrtq arv pri>rni-iny I.?# .

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In the glass industry, and to a more limited extent in the steel industry (@), it has become good practice to schedule furnace rebuilds perhaps months ahead instead of waiting for the failure of qome furnace element. For maintaining the silica walls of coke o w n s , Tweedy (40) surveyed three methods of patching: cement spnifing, t r o d i n g , and spray welding. The latter British method has not been reported tried in the United States, but the1 t, has been interest in mixtures for gunning against hot walls, and gun has been reported capable of applying 100 pounds of refrart n r v per minute in this manner. TESTIVG MhTH0I)S

l'he American Society for Testing Materials lids annourkctd i t ? third manual of refractory tests (1). Notable inclusions are studies of service conditions for refractories in Yarious industi ies, including steel, malleable iron, copper, by-product coke, lime, ylass, and portland cement. I n lieu of tests for ultimate refractoriness, testing schediiles have been adopted to determine the temperature of failure of silica, magnesite, chrome, and other refractories under a load of 25 pounds per square inch. Permeability of refractories to gases may ordinarily be or niinor significance, but report,s have been made ( 2 ) of the successful trial of novel furnaces with an inner lining of permeable insulating firebrick, such that the products of combustion may be vithdi an n through the brick wall without the use of flues. The literature on slag tests was surveyed by Hurst and Read Me),but there is still no suitable slag test except for a f e v exceptional conditions. -4 phase rule approach to the problem &-as preqented by Dobbins (12). There is also no wholly suitable test For acid resistance, the reflux condmser test having proved to be poorly simulative of service. The development of the superduty fire-clay refractories which rxcel in resistance t o thermal shock was closely linked to the development of the panel spalling test method which applies air mist to heated panels of brick folloping a preheat a t 1650" C. This A.S.T.M. method is now almost universally used in the United States following its incorporation into the newest federal specification (14). The spalling of silica brick was investigated by Ilowie (23),who determined the maximum rate a t which they could be heated on a hot plate before fracture would occur. Phelps ($8) demonstrated t h a t furnace pressures may affect the life of refractories, since high pressures disturb the heat gradient through the walls and result in the deeper extension of vitrifying influences. The thermal conductivity of refractories is difficult to measuie, but, after much cooperative work between laboratories, a method and apparatus for testing insulating firebrick have been adopted as standard by A.S.T.M. ( 3 ) . Austin (4)published an exhrtusrive study of the thermal conductivity of refractories. The task of studying the resistance of various refractories to ~~ombinationa of gases a t the various tempcratures and pressures ivhich may today be encountered in industrial processes seems endless. The British Refractories Research Association continues to work on thia subject (25). T n studying a wide variety of refractories in a pilot plant for tile production of hydrogen by pyrolysis of natural gas, TVright F. and Wolff (41) reported t h a t severeattackoccurrcdals0ve2500~ spparently because of the reduction of silica t o a volatile form by carbon. Studies by Baulcloh and Spetzler (.5) on the breakdown of car!)on monoxide to carbon dioxide and carbon have advanced the idea t h a t this reaction, which proceeds a t about 750-1000° F. to disintegrate refractories (through carbon deposition) in high carbon monoxide atmospheres, is effectively catalyzed only R hen the irony impurities are converted to metallic iron. Comprehensive data on creep are notably difficultto find ill the literature. The tests require a multiplicity of expensire tenting

unitir and are time consuming Studim in this firJld

Vol. 39, No. 10

('h s rf al. (91 recently reported

LITERATUKE CITED

Twting Materials, Standards on Refractory htaterialr ' 2 Anderson, R. H., G u m , D. C.. and Roberts, A. L.,Iron & Coal Trades new., 148 (3983), 998-9 (1944). ;i1 A.S.T.M. Method C 182. 41 Austin, *J, B., A.S.T.M. Symposium on Thermal Insulating >laterials (1939). , 3 ) Baukloh, W., and Spetaler, E., Arch. Eisenhiittenw., 13, 223-6 (1939). 1 ; ) Birch, R. E., Ohio State Univ. Eng. Expt. Sta., XeLIsa, 17 (41, 3-7 (1945). 71 Boggs, W. B., ilnderson, J. N., and Stevens, W. L., Trans Can. Inst. Mining M e t . , 48, No. 398,402-28 (June 1945). 18) Bur. of Ships (U.S. Navy) Specification 32R4 (May 15, 19461 ( 9 ) Clews, F. H., Richardson, H. M., and Green, A. T., Trans. Brit Ceram. Soc., 43, 2 2 3 4 6 (1944). (10) David, L., Metallurgia, 30 (176), 91-3 (1944). (11) Debenham, W. S., Proc. Natl. O p e n Hearth C07Lf. A m . Mining Engrs., 28, 89-110 (1945). ' 1 2 ) Dobbins, N. E., Refractories J . , 17 (5), 173-85; (6) 203-21 (1941). (13) Electrotherni. Sec., Electrotech. Lab., J . Am. Ceram.. SOC.,26 (12), 405-13 (1943). (141 Federal Specification for Brick, Fire Clay, HH-B-671c (Oct. 10, 1946). (15) Fondersmith, C. R., Proc. Natl. Open Hearth Conf. A m . Inst Mining Engrs., 28, 87-8 (1945). (16: Geller, It. F., and Yavorsky, P. J., J . Research Natl. Birr Standards, 35, 87-110 (1945). (lit Goudge, M. F., J . Am. Ceram. SOC.,27 ( l ) ,8-10 (1944). (181 Harvey, F. A., and Thompson, C. L., J . Am. Ceram. Soc., 26 ( l l ) , 361-4; McDowell, J. S., 364-7; Trostel, L. J., 368-73: Phelps, S. M., and Limes, R. W., 378-87 (1943). (19; Harvey, F. A., Birch, R. E., and Goldschmidt, V. M,, IKD. EN(; CHEM.,30, 27-34 (1938). (201 tleindl, R. A., and Pendergaut, W. L., Natl. Bur. Standarda (U. S.),R. P. 1219 (1939), 1461 (1942), 1534 (1943). 1211 tleindl, R. A., Massengale, G. B., and Cassette, L. G., Glnxs Ind., 27 (4), 177-81,2004,208,214 (1946). d - ) Heuer, R. P., Brick & Clay Record, 100 (3), 50-1 (1942). (23) I-Iowie, T. W., Trans. Brit. Ceram. SOC.,45 (2), 45-69 (1946) (24) Hurst, T. L., and Read, E, R., J . Am. Cemm. SOC.,25 ( I l ) , 28394 (1942). (C),,

tron & Steel Inst. [Brit.), 3rd Rept. on Refractory Matclrials. Special Rept., 32, See. F, 381-7 (1946). 1.26) Kraner, I€. AM., PTOC.Na,tl. Open Hearth Conf. Am. Inst. Jli7ring Engrs., 27, 303-9 (1944). 7) Lea, F. M., J . SOC.Chem. Ind. (London), 59 ( l ) , 18-21 (19.40 28) Lyons, M. D., Eng.Mining J., 148 (I 83-5 ), (1947). (29) McDowell, J. S., Blast Furnace Steel plant, 27, 592-7 (June,. 947-51 (Sept. 1939); 28, 161-8, 178 (Feb. 1940). :XI) McVay, T. N., and Wilson, Hewitt, J . Am. Ceram. SOC.,26 125j

( 8 ) , 252-66 (1943). ;811 Moser, A., Tonka'.-Ztg., 63, 763-3, 775-6, 789-9 1 (1939).

(32; Phelps, S. M., Am. Rejractories Inst., Tech. Bull. 79 (Feb. 1943) ( 3 3 ) Russell, Ralston, Jr., O 5 c e of Milit'ary Govt. for Germany, Fiat F h l Rept., 617 (1945), PB 18776. Sawyer, J. P., Jr., and Whittemore, J. W., Bull. Virginia, Polytech. Inst., Eng. Exper. Sta., Series 49 (1941). (:st;) dchallis, A., U. S. Bur. Mines, Inform. Circ. 7227 (Jan. 1943).

Pcil, G. E., Phelps, S. M., and team, O5ce Tech. Services. Fiat Rept., 432, PB 37804, PP. 41 (1946). (371 Snodgress, M. L., Ind. Heating, 12, 834-6 (1945). (38) Sosman, R. B., PTOC. Natl. O p e n Hearth Conf. Am. Inst. Minino Engrs., 28, 54-71 (1945). (39') \windon, T., and Chesters, J. H., J . Iron Steel Inst. (London)' 144 ( 2 ) , 105-18 (1941). ( q j j Tweedy, S., Gas World (Coking Sec.), 31 (359), 7-12 (1943). (41) JTrright, R. E., and Wolff,H. I., Am. Cfiram.floc. Bull. (Abstract). (36)

26 (a), 79 (1947). (42) yarotsky, M. F., PTOC.Natl. Open Hearth conf. Am. I m t . ,Ifining Engrs., 26, 48-53 (1943).

HARD RUBBER F. S. MALM, Bell

Telephone

Laborutories, ,Ilurruy Hill,

T

A’.J .

HE advent of World War I1 brought a period of problenis and shortages to the Rubber Industry solved only by a monumental effort that is now history. I t was believed that a summary of the literature on hard rubber for this period might be valuable to future investigators in the field, and, with this end in view, the present survey was prepared. One article (eO5) describes the impact of the events of the early war period rhronicling the efforts toward conservation of natural rubber and the introduction of ebonite from synthetic elastomers. Buna S obtained from Europe as early as 1938 was formulated by the writer and colleagues into various types of hard rubber suitable for making rods, tubes, and sheets for insulations in electrical apparatus, but it was not until the war that the use of synthetic rubber became a necessity. At this time the War Production Board, through the office of Rubber Director, appointed a Hard Rubber Technical Committee selected from industry t o cooperate in allocation of natural rubber for specific uses, where use of GR-S alone would work a hardship on manufacturers of hard rubber. This cooperative work greatly facilitated production and was carried out in a commendable manner. Although many of the polymeric materials which have appeared during the past five pears have proved satisfactory for certain applications, such as piping, tank linings, battery cases, combs, etc., statistics show that the annual production of hard rubber as an engineering material and high quality dielectric has not dccreased. This suggests that many of the inherent properties of ebonite that can be realized through compounding will continue to make this material desirable for a multiplicity of applications. A bibliography of the recent literature on hard rubber is appended. Examination of this list reveals that, significant as was the introduction of commercial synthetic ebonites, it was nevertheless outneighed in the literature by the many papers and patents on new applications and processes which constitute ovilr half of the publications for that period. The bibliography lists twelve p a p m (9, 22, 65, 81, 83, 206, 124, lC54,160, 189, 156, 204) having to do with the compounding of synthetic ebonites of various types. The second referc.nce cited deals with sulfur-free ebonites from Russian S.K. rubber, whereas the eighth is a series of circulars on compounding and processing published by the Ministry of Supply in London. I n addition, three other references deal Tvith variations in base elatomer: Ratnaparkhe reports the preparation of ebonite from African wild rubber (188), and others (266, 257) describe the preparation of hard rubbers from latex and from all reclaim, respectively. Acceleration is discussed by Davies ( 5 2 ) and cowred by a patent ( 4 ) , while blowing agents are the subject of a paper 1105) and four patents (48, 52, 226, 649). References 7 and 99 have to do with colored ebonites. Fillers and extenders for haid rubber are covered in items 66, 86, 90, 103, 111, 115, 137, I o i , 174, 181, 199, 215, 217, 24.49, 255, and 267. Among the contributions to theory are a series of papers by Suniaziri (167) dealing with the mechanism of the hard rubber reaction, a paper by Booth and Beaver (2%) reporting the results of researches in accelerator action in soft rubber during which evidence was obtained attaching significance to the role of hydrogen sulfide in the curing of ebonite, and a paper by Okita (170) dealing with the same subject. The physico-chemical aspects of ebonite are dealt with by Scott in papers on its plastic-elastic behavior (216) and on the relation between rheological behavior and structure (218). Bridgman

(30) reported the flow behavior of liard rubber under e x t r c r d j high pressures, and found high plasticity and prominent, time effects. Leaderman (133) studied creep and recovery in hard rubber threads. Other authors have reported on the dielectric properties of hard rubber (55, 146, 156, 161, 2.492), and investigated its heat resistance (76) and its energy transmission and absorption (219 ). Moisture permeability was investigated by Barrer (15) and br Evilova (70),who reported that pure water will not pass through microporous ebonite because it becomes electrically charged. Results of water absorption studies were reported by Daynes (56) and by Quarmby (185), while Parris and Scott (177) and Wakeman (258) observed other changes due to immersion in various liquids, including water. Several authors (40, 119, 1.94, 160, 197, 214) published generai articles on the properties of various types of natural and synthetic ebonites, and concise tables are given in the Boonton Molding Company’s “Ready Reference for Plastics” (%) and the “Plastics Catalog” ($9,184). Bourgois ( 2 7 ) , Gartner (75), and Saito (207) give reviews for the French, German, and Japanese products, comparing the properties of natural and syntheti,, ebonites with those of other plastics. I n a more recent publication (267) Winspear, Herrniann, Malm, and Kcmp coniniented in detail on the differcnees between GR-S, nitrile arid natui,ai ebonites and loaded hard rubbers, covering compounding and vulcanization, heat of exothermic reaction, c!iernical stability, and physical and dielectric properties. Valuable contributionmere made also by Church and Uaynes in a continuation of their wries of papers on the chemistry of hard rubber (43)report#ing011 experiments in aging, thermal effects during vulcanization, surface deterioration in sunlight, and the influtxice of t h c rubbersulfur ratio on me-hanical and dielectric pr0pt:rtii.s. The literature contributions on testing include studies of the effects of variables on dielectric strength determinations (161 and on impact testing (163, 240). Guinier and Berthelin (86) and Schwittmann (213) have published critical reviews of the latter topic. Rerently published test methods include papers by Arcrid (Sj on testing the corrosion resistance of ebonite, by Callcnder ( 3 6 ) on brittleness, by Frolich (75) on the dynamic determination of t,he modulus of elasticity, and two papers from the A.S.T.M. on impact methods by Lubin and Winans (1S8),and by Stock (2331. Coutlce, Field, IPausmann, Ilazen, and Meahl ( 4 9 ) discuss measurement of power factor at, ultrahigh frequencies, while Daynes (58) reports on surface resistivity measurements. Items 32 and 3.49 refer to British Standard Test 1Ierhods and British War Emergency Standards, respectively, for hard rubber, Khile item 163 is a British specification for expanded hard rubber for usc in aircraft. Sweeney and Caul (237) proposed a standard specification for denture base materials. New test equipment is described in references 11 (plastometer), 14 and 130 (hardness testers), 64 (apparatus for determining heat resistance), 224 (audio frequency bridge), and 241 (impact tcster). The balance and major part of the bibliography consists of items referring to the practical aspects of hard rubbcr, covering processing equipment ( 1 , 20, 67, 88, 109, l l d 3 123, 139, 179, 208, 209, 212, 242, 269), machining and finishing techniques (18, 91, 47, 50, 147, 148, 160, 172, 182, 8.90, 222, 260, d68), and many specific applications. Prominent among the last are battery applications, including cases, sealing devices, and separators.

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1244

T h e history of the development of microporous battery separators through 1931 is given by Dawson and Thompson (64). Porous ebonite is described for other purposes such as filter media, lightweight structural compositions, etc. (IO,12, 34, 37, 71, ,%,‘ 74, 84, 102, 128, 180, 183, 231, 247, 252). Use of polyvinyl chloride plastics as adhesives in conjunction with hard rubbor is advocated by Enderlein (69) and the same materials patented as surface coatings by Hempel (97). Several good review articles are included in the bibliography. Those on compounding and impact testing have been mentioned. Daynes (59,60) has published two broad reviews of hard rubber, and those by Davies (61) are concise and informativr, giving brief synopses of manv of the more important papers. BIBLIOGRAPHY

l i Abbe Engineering Co., New York, Bull. 50 (1941) ; Modern Plastics, 19, 86 (19-12). Advertising special type grinders

for ebonite. 2 ) Acheson, E. G., Ltd., Electrician, 130, 109 (1943). Preparation of hard rubber surfaces for metal coating. : 3 ) Allison, H. V., U. S. Patents 2,229,879-80 (Jan. 28, 1941).

Methods of making porous rubber-bonded abrasive articles, via concentrated latex and employing Buna N, respectively. 4) .Illison, H. V. (to Allison Co.), Ibid., 2,311,605 (Feb. 16, 1943). Use of zinc selenide (about 0.5%) to increase strength of hard rubber. ‘ 5 ) Alyaudin, N., Tsuetnaga .Met., 1940, No. 7, 12. Powdered ebonite the best matrix for holding powdered ores for microscopical examination. 6 ) American Hard Rubber Co.. Brit. Patent 497,908 (Jan. 11, 1939). Production of hard rubber articles featuring pearly luster. 7) Anchor Chemical Co., Ltd.. Manchester, Lab. Rept. 21 (1940). Use of cadmium red as substitute for vermilion in dental compositions. %) Arend, A. G., Rubber A y e (London), 22, 244 (1941). Testing the corrosion resistance of ebonite. .9) Aziation, 42, No. 6, 195 (1943). Heat resista,nt hard rubber from Hycar. :lo) Axilrod, B. M., and Koenig, E., Natl. Advisory Comm. heronaut., Tech. Note 991 (1945). Cellular hard rubber was among materials investigated for aircraft applications. 11) Bailey, C. R., IND.ENG.CHEM.,ANAL.ED., 13, 173 (1941). Instrument for study of plastic-elastic phenomena in ebonite. :12) Banks, J. L. M. S.,Brit. Patents 551,211 (Feb. 2.1, 1943) and 551,733 (Mar. 17, 1943). Attempts to utilize hard. rubber in light structural materials. a13) Banks, J. L. M. S.,and Jicwood, Ltd., Ibid., 542,897 (Feb. 11, 1942). Porous hard rubber by release of gas pre*sure after partial curing. 14) Barber-Colman Co., S e w s Ed. ( A m . C‘hem. Soc.), 19, 394 (1941). New hardness tester. ‘‘15) Barrer, R. M.,Trans. Faraday SOC.,36, 644-8 (1940). Permeability of organic polymers including hard rubber. IC,) Baty, J. A., and Mey-er. A. IT. (to U. S. Rubber Co.). C’anadian Patents 397,702-3 (July 1, 1941). Same as Brit. Patents 504,549 (May 10, 1939) and 532,475 (Feb. 5, 19413. Hard microporous products. Also use of inorganic hydrogel t o produce the pores in battery separators. U. S. Pateni 2,329,322 (Sept. 14, 1943). 17) Beiersdorf, H., and Haeger, H. (to Siemens-Schuckertwerke A-G.), German Patent 694,853 (July 11, 1940). Hard rubber coatings by spraying compounded latex. 1%) Bentley, L. F., Brit. Patent 556,374 (Oct. 13, 1943). New machine for cutting hard rubber as strips from sheet, with less waste than sawing, involves local heating ahead of rotary knives. ,19) Berman, G. S., Ibid., 547,088 (Sug. 26, 1942). -411 rubber umbrella. 20) Blackfriars Engineering Co., Ltd., Rubber Age (London), 23, 65 (1942) ; India-Rubber J., 103 (1942). Cover advertisement, special type grinders for ebonite. 21) Blake, G. G., J . PTOC. Roy. SOC. S. Wales, 77, 106 (1943). Use of strip of ebonite as sensitive element in infrared radiometer. 22) Blokh, G. A., and Zaionchkovsky, A. D., Kauchuk i Rezina, 1941, No. 4, 7. Sulfur-free hard rubber from Russian S.K. with peroxides and nitro compounds. 23) Blomfield, R. M., Burt, F. E., and Britannia Batteries, Ltd., Brit. Patent 564,077 (Sept. 27, 1944). Sealing device to prevent loss of electrolyte from batteries.

Vol. 39, No. 10

(24) Bloornfield, G. F., and British Rubber Producers’ Research .-hoc., Ibid., 558,080 (Dee. 30, 1943). Electrical resistance

units from incorporation of conducting materials in hard rubber st,ock. (25) Hoonton Molding Co., “Ready Reference for Plastics” (1947) ; Rubber Age (N. Y.), 47, 415 (1940). Includes data on synthetic and hard rubber. (26) Booth, E. W., and Beaver, D. J., ISD. ENG.CHEM.,32, 1006 (1940); Rubber Age (N.Y.i, 46, 376 (1940); India-Rubber J . , 99, 346 (1940). Research on accelerator action in soft rubber; role of HgS m a y be significant in curing of ebonite. (27) Bourgois, P., Gummi-Ztg. 21. Kautschuk, 1943, Apr.-May, 3910K. Rubber and synthetic materials as protective agents against at.tack by chemicals; a review and discussion with table including hard rubber, Oppanol, and Vinidur. Chim. peintures, 6, 278-82 (1943); Chem.-Zcntr., 1944, I. 238. (28) Rrentnall, G. C., and Dunlop Rubber Co., Ltd., Brit,. Patent 637,144 (June 25, 1941). Guides for machine gun ammu-

nition belts with hard rubber beads. (29) Breskin Pub. Corp., “Modern Plastics Catalog,” 1941, 150. Brief summarized comparison of properties of hard rubber

with those of other plastics. (30) Bridgman, P. W., J . Applied Phys., 17, 201-12 (1946). Hard

rubber acquired great plasticity and showed prominent time effects under hydrostatic pressures up t o 29,000 kg.!sq. em. exerted by isopentane. (31) Brit. Plastics, 11, 468 (1940). Chrome plating recommended for tools and gages for use with ebonite. Ibid., 11, 535 (1940). Surface treatment of hard rubber prior to deposition of metallic surface layer. (32) British Standards Institution (London), British Standard Methods of Testing Vulcanized Rubber, Spec. No. 903 (1940). (33) Ibid., B. S. 234 (1942). War emergency specificat,ion for ebonite for electrical purposes. (341 Brooks, A. E., U. S. Patent 2,185,586 (Jan. 2, 1946); Canadian Patent 397,163 (June 10, 1941); Brit. Patent 525,537 (To U. S. Rubber) (Sept. 11, 1940); Microporous rubber filt,er-

ing medium. (35) Butcher, C. H., Chem. Age, 45, 165 (1941). Uses of hard rub-

ber in valves and cocks. (36) Callender, L, H., Brit. Plastics, 13, 441 ff. (1942). Brittleness

test. (37) Carrington, J. H., Roberts, F. S.,and Revertex, Ltd., Brit. Patent 565,677 (Dee. 6, 1944). Porous ebonit,e linings for

plaster molds. (38) Chem. Age, 44, 359, 367 (1941). Comparison of linings of hard rubber and other materials for protection against corrosive

liquids. (39) Chevassus, F., Rev. Ghn. caoutchouc, 22, 162-3 (1945). Ebo-

nite coatings with a latex base; compounding and technique for high adhesions wit,h thin coats by spraying or dipping. (401 Cheyney, La.V, E., and Robinson, A. L., IND.ENG. CHEW., 35, 976 (1943); India R ~ b h PT’orZd, ~r 108, 57 (1943). Properties of GK-Sebonites. (41) Chichester-Xles. H. G. W., U. S. Patent 2,264,931 (Dee. 2, 1941). UFe of loaded hard rubber in protective helmets. (42) Chloride Electrical Storage Co., Ltd., Brit. Patent 526,579 (Dee. 2, 1940). Porous ebonite as bonding agent for wood particles or glass wool in battery separators. Ibid. (with B. Heap), 530,721 (Jan. 1, 1941). High loading with dry starch which is leachrd out after dry vulcanization to give porous ebonite. Ibid. (to C. .1.Hall), 537,181 (June 25, 1941). Use of vinyl resin fibers imbedded in hard rubber membrane for battery separators. Ibid., 568,033 (Mar. 28, 1945). Sealing device to prevent leakage of electrolyte. Ibid., 570,894 (1945). Plastic fibers bonded with hard rubber as separators. (43) Church. H. F., and Daynes, H. A., J . Rubber Research, 12, 133-9 (1943); Rubber Chem. Tech., 17, 913-22 (1944); Properties of hard rubber; experiments on aging. J. Rubber Research, 13, 55-8 (1944). Experiments on thermal effects during vulcanization. Rubber Chem. Tech., 17, 923-8 (1944) : with Cooper, L. H. X., J. Rubber Research, 14, 1559 (1945). Influence of some ingredients on surface deterioration in sunlight. Rubber Chem. Tech., 19, 753-9 (1946); J . Rubber Research, 14, 165-72 (1945). Influencr of rubhersulfur ratio and vulcanization time on the properties of pure rubber-sulfur compositions: chemical composirion, density, thermal expansion. Ruhbsr Chem. Tech., 19, 760-72 (1946) ; J . Rubber Research, 15, 127-53 (1946). Influence of rubbersulfur ratio and vulcanization time on the properties of pure rubber-sulfur compositions: mechanical and electrical proprrries. l h f d , , 15, 163-79 (1946). Influence on rubber-

October 1947


sulfur ratio and vulcauization time on the propert,ies of pure rubber-sulfur compositions: swelling, water absorption, aging, and general discussion of results. r44) Clarke, R. B. F., Trans. I n s t . Rubber Ind., 16, 51 (1940). Use as a tie-stock of flexible hard rubber containing Neoprene. ’ 45) Compagnie General d’Electricite, Brit. Patent 495,710 (Nov. 30, 1938). Bat.tery separator of glass threads bonded by porous rubber. .46) Coinpagnie Rhnies des Glaces et Terres speciaux du Kord de la France, French Patent 845,427 (Aug. 23, 1939). Use of glass fibers imbedded in hard rubber membrane as battery separators. 47) “Consultant,” Factory M a m g e r , 8, 255 (1940). Discussion of techniques for machining ebonite goods. ;48) Cooper, A., and Expanded Rubber Co., Ltd., Brit. Patent 528,746 (Dec. 20, 1940). Cellular hard rubber by gas impregnation. Ibid., 545,302 (June 3, 1942). Blowing agent for cellular hard rubber. 149) Coutlee, K. G., Field, R. F..Hausnann, E. O., Hazen, T., and 41, 1172Uealil, H. R.,A m . Soc. Testing Materials, PTOC., S2 (1941). Measurement of power factor at ultrahigh frequencies with discussion of theory. 150) Creevey, J., Chem. d g q 47, 55 (1942). Lessening explosion hazards during ebonit,e grinding. :51) Davies, B. L., Ann. Rept. Prog. R u b . Tech., 4, 131-5 (1940); 5 , 115-18 (1941); 6, 104-7 (1942); 7, 104-6 (1943); 8, 110-13 (1944); 9, 95-8 (1945). Annual reviews of hard

rubber developments. (52) Davies, B. L., Rw. GBn. caoutchouc, 18, 268-71 (1941); Chem.Zentr., 1942, I, 2940. Acceleration of vulcanization of

ebonite. ‘53) Davies, B. L., and United Ebonite & Lorival, Ltd., Brit. Patent 572,797 (Kov. 7, 1945). Insertion of paper be-

tween ebonite battery wall and soft rubber lining as a safety measure. 541 Dawson, T. R., and Thompson, E. A . M., J . Research 3ssoc. Brit. M j r s . , 14, 179 (1945). Summary of development of microporous battery separators up to 1931. ,55) Daynes, H. A., J . Rubher Research, 10, 45-87 (1941). Properties of hard rubber; (Tlectrical properties in relation to coniposition. (56) Ibid., 11, 67-9 (1912). Absorption of water by hard rubber as affected by the type of rubber and the method of rulcanization. ,57\ Ibid., 12, 131-2 (1948); Rubber C‘hem. Tech., 17, 929-31 (1944). Changes in physical properties of hard rubber shortly after vulcanization. ’58) Daynes, H. A., J . R u b b s ~ Krscarch. 13, 81 (1944). Surfar,e resistivity measurement?. (59) Daynes, H. .4., Siemens Rev. (Eng. supplement), 1942, KO. 204, 1. A review of niajor physical properties of hard rubber using three types as examples. ;60) Daynes, H. A., Trans. Inst. Rubber I n d . , 17, 151-60 (Oct. 1941). Rubber-base insulating plastics. General review and discussion. (61) Dillehay, E. R., U. S. Patent 2,310,619 (Feb. 9, 1943). Vulcanization of sheets in contact with regenerated cellulose film. (62) I b i d . (to Richardson Co.), 2,365,335 (Dec. 19, 1944). Loadiiig with powdered cured phenolic resin. ‘63) Doolittle, A. K. ( t o Carbide & Carbon), Canadian Patent 400,428 (Nov. 4, 1941). Coated hard rubber article, with vinyl chloride acetate copolymer. ,64) Dubinker, Y. B., Kauchuk i Rezina, 1940, No. 11, 14-16. Apparatus for determining the heat resistance of ebonite. (65) Du Pont, E. I., de Nemours & Company, Inc., Rubber Chem. Div., Rept. BG55 (1942). Hard vulcanizates from Neoprene. 66) Durez Plastics and Chemical Co., Inc., Rubber Age (N. Y.), 56, 634 (1948). New type resins t o give hardening and reinforcement of soft stocks. 167) Eder, O., German Patent (to Semperit Gummin-erke A-G.) 732,268 (Jan. 25, 1943) ; Machine for applying metal foils on hard rubber plates, etc. ,68) Elliman, H., Brit. Patent 552,844 (May 12, 1943). Use of ebonite in razor blade sharpener. 69) Enderlein, >I., Kunststofe, 32, 289 (1942); Plastics, 8, 166 (1944). Use of polJ-vinyl chloride adhesive in repairing broken ebonite. :io) Evilova, ByuZZ. Obmrna Opyt. Lakokrasoch. Prom., 1939, No. 6-7, 25. Pure water cannot be passed through microporous ebonite because it becomes electrically charged. (71) Expanded Rubber Co., Ltd., Mechanics, 37, 89 (1944). Use of porous ebonite as an interply in composite lightweight boards.

1245

(72) Faidutti. AI., and SociBtB Chimique de Gerland, French Patent 881,890 (May 11, 1943); Rev. Ghn. caoutchouc, Doc. Anal., 21, 100 (1944). Proposal to improve processing and control

hardness of loaded stocks by use of a plasticizer which can be extracted after vulcanization. (73) Filter Medium Carp., Rubber A g e ( S . Y . ) , 46, 295 (1940). 4 superior type of porous hard rubber for filters. (74) Frank, F., and British Artificial Resin Co. Ltd., Brit. Patent 551,179 (Feb. 24, 1943). Vse of porous ebonit,e in coverings for industrial rollers. (75) Frolich, K., Kunststofe, 30, 10-12 (1940). Dynamic determination of the elasticity modulus of synthetic materials by means of bending vibrations; includes hard rubber. (76) Frunikin. L. S., and Dubinker, Y. B., Kauchuk i Rrzina. 1940, KO. 1, 21-8. Investigations of the heat-resistance of ebonite. Khim. Referat. Zhur., 1940, No. 6. 120-1. (77) Fryd, E., and Oppenheimer Pipes, Ltd., Brit. Patent 53,209 (Jan. 29, 1941). Hard rubber pipe stems. (78) Garbisch, S . S.,U. S. Patent 2,220,759 (Nov. 5 , 1940); Brit. Patent 535,417 (Apr. 23, 1941). Use of hard rubber loaded nit,h mixture of silica and glass (spent residue from plate glass grinding) in battery boxes. (79) Gartner, E., Kautschuk, 16, 109 (1940). Comparison of mechanical, electrical, and chemical propertie$ of natural and various synthetic hard rubbers. (80) Gartrell, R. D. (to U. S. Rubber Co.), U. S. Patent 2,235,148 (Mar. 18, 1941). Method of making rubber printing plates. (51) Ga.rrey, B. S.,Jr., and Sarbach, D. V., IND. ESG. CHEM., 34, 1312 (1942). Heat resistant hard rubber from Hycar. (82) Geiger, L. M., I n d i a Rubber WorZd, 105, 489 (1942). Tse of coumarone resins as extender. $33) Ghez, H. C., Ibid., 105, 379 (1942); 106, 142 (1942); Rubber A g e (N. Y.), 50 (1912). Advert’isements; Xervastral process for ebonite w-ithout rrude (using reclaim). (84) Gibbns, T. A. (to U.S. Rubber Co.), U. P. Patent 2,232,109 (Feb. 18, 1941). Manufacture of microporous articles with predetermined relief designs. (55) Goodyear Tire & Rubber Co., Kational Batter!, (Co., Sci. American, 173, 158 (194.5). Glass fiberr bonder1 with hard rubber for bat,tery separators. (86) Guinier, A , , and Berthelin. J. P., Rcc. Gbt. caoutchouc, Uoc. Anal., 21, 88 (1944). C.‘ritical review of impact testing methods (871 Halls, E. E., Pairit Manuf., 9, 299, 309 (1939). Use of varnishes and lacquers to preserve surface insulating properties. (88) Halls, E. E., Plastics (London), 4, 234 (1940). Chrome plating of molds for loaded hard rubbers to facilitate machining of products. (80) Ibid., 4, 140 (19401, 7, 549 (1943); 8, 112 (1944). Application of metallic surface layers. (90) Ibid., 6, 267, 352 (1942). Fillers for hard mbber, Includes slate flour and zinc sulfide. (911 Ibid.. 8, 305, 3ti9 (1944). Use of naphtha for cleaning hard rubber. (921 Hamilton, G . bf. (to Callender’s Cable and Construction Co. Ltd.) U. S . Patent 2,404,171 (July 16, 1946). Use of FeC204 t o impart cellular form to hard rubber during vulcanization. (93) Hampton, H. J., and Chloride Electrical Storate Co., Ltd., Brit. Patent 551,731 (Feb. 17, 1943). LIicroporous battery separators. (94’1 Harding, H. L., and India Rubber, Gutta-percha and Telegraph, Brit. Patent 571,435 (Sept,. 8, 1945). Blending of neoprene with natural rubber for improved battery containers. i96) -, Harkiris. H. H. (to U. a. Rubber). LT. S. Parent, 2.218.16, ~-,-(Oct. 5, 1940). ‘ Flexible hard rubber. (96) Hazell. E., Canadian Patent 397,889 (July E;, 1941) ; ( t o U. 8. Rubber Co.). Brit. Patent 518.153 (Feb. 28, 1941). Battery paste container featuring outer laye1 of perforated hard rubber and inner layer cf soft sponge rubber. (97) Hempel, C. H. (to Heresite & Chemical Co.), U. S. Patent 2,312,296 (Feb. 23, 1943). Method of coating hard rubber with a synthetic resin. (98) Herold. IT. E., Brit. Patent 549,73b ( D e r . 16, 1942). Hald rubber caster wheels. (99) Hiernann, W., Canadian Patent 386,947 (Feb. 20, 19401. Color shadings for hard rubber articles. (100) Hollywood Comb-Curler Inc., Brit. Patent 529,419 (Dee. 4, 1940). Hard rubber hair curlers. (101) Holm, R.. Kiss. Verofent. Siemens-Werken, 20, 68-84 (1941) ; Chrnr.-Zentr.,1942, I, 1032-3. Study of friction and wear of Fe contacts on various materials including hard rubber. (102) Hubbard, S,,Ltd., Autocar, 88, 4 (1943). Advertisement, porous hard rubber with felt interply as structural material. (103) Hukusima. K., Japanese Patent 134,347 (Jan. 25, 1940). Treated vrgeta,ble fibers as filler for hard rubber. \ -

~I~

1246

INDUSTRIAL AND E N G I N E E R I N G CHEMISTRY

(104) Imperial Chemical Industries, Ltd., Neoprene ‘Vews, 10, 8 (1940). Linings in storage of errosive liquids. (105) Imperial Chemical Industries, Ltd., Rept. R-26 (1941). Blowing agent for cellular hard rubber. (106) Ibid., R-45 (April 1942). Typical all-reclaim hard rubber mix. (107) Imperial Chemical Industries, Ltd., Tech. Bull. Shockproof ebonite. Ibid., Rept. N-35; Rubber Chemicals, Bull. 10, Rept. N-16 (1940). (108) India Rubber, Gutta-percha & Telegraph Works Co., Ltd., and R. J. Tudor, Brit. Patent 561,839 (June 21, 1944). Neoprene will vulcanize t,o a hard product. (109) India-Rubber J., 100, 128 (1940). Hard rubber molds. (110) India Rubber World, 101, 64 (1940). Hard rubber pads for men’s hats. (111) Ibid., 104, 48 (1941). English walnut shell flour as filler. (112) ISD. ENG.CHEM.,33, NO. 3, 16; No. 9, 28 (1941). Advertisements, case, histories, and photos of hard rubber storage tanks for corrosive liquids. (113) International Latex Processes, Ltd., Brit. Patent 535,924 (May 7, 1941). Battery separators. (114) Jones, F., Plastics (London), 4, 236 (1940). Hard rubber molds. Use of Al powder for better heat conduction. (115) Jones, F., Trans. Inst. Rubber Ind., 15, 352 (1940). Utilizing ground scrap in hard rubber industry. (116) Joy, B. C., and Simms, F. R., Brit. Patent 531,971 (Jan. 29, 1941). Corrosion-resisting diaphragm pumps. (117) Jumau, L. J., U. S.Patent 2,247,091 (June 24, 1941). Battery separators. (118) Juve, W. H., A.S.T.M. Bull., 127, 12 (1944). Properties of GR-S hard rubber. (119) Keen, A. W. (to U. S. Rubber Co.), Canadian Patent 398,855 (8ug. 26, 1941). Battery paste retainer. (120) Kent, C. A., Brit. Patent 528,116 (Nov. 6, 1940). Combs. (121) Kirkman, D. W. T., Thompson, W. S., and Nife Batteries, Ltd., Ibid., 557,745 (Dec. 15, 1943). Batteries. (122) Kistler, S. S.,Canadian Patent 396,667 (May 20, 1941). Rubber and resin-bonded abrasive article. (123) Klaas, E. O., and Meyers, E. H., U. S.Patent 2,194,757 (Feb. 26, 1940). Special machinery for battery cases and covers. (124) Klebsattel, C. A., India Rubber World, 103, 47 (1940). Perbunan hard rubber. ,124) Klinger, E., Knapp, 0.. Leonberg, K., and Luta, bf. (vested in the Alien Property Custodian), U. 8. Patent 2,395,785 (Feb. 26, 1946), Hard rubber insulation for metal and conductors. (126) Kolovsky, L. R., Ibid., 2,269,628 ( J a n . 13, 1942). R i t h silica for blackboards. ‘127) Koptsiovskii, L. Z., Korroziya i Borba s Net, 7, No. 2, 49-55 (1941). Chemical apparatus parts. t128) Kremer, H., Brit. Patent 558,166 (Jan. 4, 1944). Porous ebonite in structures. Ibid., 569,030 (May 16, 1945). As an interply in light-weight boards. (129) Krymov, P. M., Russian Patent 52,033 (Oct. 31, 1937). Hard rubber disks for cutting and grinding stones. (130) Kuntze, IT., Kunststofe, 30, 323 (1940) ; Chem.-Zentr., 112, I, 1261 (1941). Hardness tester with pyramidal indentor. ;131) Kuzmick, J. N. (to Raybestos-Manhattan), U. S. Patent 2,197,552 (Apr. 16, 1940). Bonded abrasive. In U. 8. Patent 2,258,774 (Oct. 14, 1941) the rubber bond incorporates metallic elements which later serve as a lubricant. (~132)Laning, E. R., Ibid., 2,367,786 (Jan. 23, 1945). Shock resistance through graded vulcanization. (133) Leadermaq, H., Testile Research, 11, 171 (1941); J. Teztilc Inst., 32, 277d (1941). Study of creep and recovery includes hard rubber threads. (134) Lee, 0. R. J., Proc. Inst. >Vfech.Engrs. (London), 143, 114 (1940). Study of effect of variables on results of impact tests. (135) Lillicra,p, J. R., Brit. Patent 550,822 (Feb. 10, 1943). Hard rubber eye bath. (136) Logan, K. H., and Romanoff, J,,J . Research A’atl. Bur. Standards. 33. 145 (1944). SuDerior corrosion resistance in soil. (137) Lougee, E.F., Modern Plaitics, 19, 35, 100, 102 (1942). Walnut shell flour as filler in battery Sox mixes. (138) Lubin, G.. and Winans, R. R., A.S.T.M.BuZl., 128, 13 (1944). Proposed new method for impact test involves falling steel balls. (139) Lunt, R. L., U. S. Patent 2,206,908 (July 9, 1940). Details of plating rubber molds. (140) McGibbon, J. E., Brit. M e d . J . , 1940, 11, 365. Hard rubber ear plugs. (141) Madge, R. G., Brit. Patent 553,823 (June 16, 1943). Ebonite bullets for toy guns. (142) Malby, C. D., and London Name Plate Co., Ltd., Ibid., 549,531 (Dec. 9, 1942). Method of putting designs, as name plates, on hard rubber articles.

Vol. 39, No. 10

(143) Mfg. Chemist, 11, 40 (1940). Flexible hard rubber. (144) Marick, L., U. S.Patent 2,266,561 (Dec. 16, 1941). Conductive carbon to eliminate static charge on hard rubber combs, (145) Martin, R. H. (to Norton Co.), T;. S. Patent 2,254,612 (Sept 2, 1941). Rubber-bonded abrasive article. (146) Massey, L., Trans. Inst. Rubber Ind., 16, 325 (1941). Cheniical aspects of electrical insulators. (147) Matthis, 4.R., and Flight, W. S.,“A Technical Work for thr Electrical Industry.” Preston, Attwater & Sons, Ltd. Tools for machining hard rubber. (148) Maxfield, R. F., Modern Plastics, 20, 73 (1943). Toola i i r machining hard rubber. (149) LMaxted,R., Electrician, 127, 351 (1941). Possible econornieof heating by infrared radiation. (150) Mechanics, 36, 78 (1944). Tools for machining hard rubber (151) Meijden, H. van der, Rubber, 2, No. 6, 4 (1939). Uses ir chemical plant. (1.52) Melton, R. L., and Chapman, G. L. (to Carborunduni (20.). U. S. Patent 2,233,176 (Feb. 25, 1941). Bonded abrasive articles via high frequency current. (153) Ministry of Aircraft Production (London), Spec. D.T.D.-421. Vulcanized expanded hard rubber. (154) Ministry of Supply (London), Repts. on Compounding arid Processing of Synthetic Rubber by Rubber Manufacturers. (155) Mirza, R. N., Brit. Patent 549,372 (Dec. 2, 1942). Grooved filter automatically indicates choking. (156) hforey, D. R., Ibid.. 37, 255 (1945). Mechanism of fracture. (157) Morgan, S.O., and Yager, W. A., IND.EXG.CHEY.,32, 1519 (1940). Dielectric constants of materials including hard rubber. (158) Morris, H. B. (to Firestone), U. S. Patent 2,258,026 (Oct. 7, 1941). Method of producing abrasive articles. (159) Morris, R. E., Hollister, S.W., and Mallard, P. A,, IND.E m . CHEM.,36, 649 (1944). Overheating during cure of thick articles from Glt-S ebonite. (160) Morris, R. E., Mitton, P., Seegman, I. P., and Werkenthin, T. A., Rubber Age (N. Y.), 54, 129 (1943). Composition and properties of some GR-S ebonites. (161) Muravjeva, G. J., Kauchuk i Rezina, 12, 23 (1940); Chem.Zentr., 112, I, 2461 (1941). Influence of variables on measurement of dielectric strength. (162) Murray, C. W. ( t o U. S.Sec. of Agr.), U. S.Patent 2,286,636 (June 16, 1942). Use of hard rubber dust in insecticides. Modern Plastl:cs, 20, 81 ff. (1942). Influence of (163) Myers, C. S., striker velocity in impact tests. (164) Nelki, W., Brit. Patent 528,237 (Nov. 6, 1940). New denture design involving steel and hard rubber. (165) New Jersey Zinc Co., India Rubber World, 102, 45 (1940); Rubber Age (N. Y.), 46, 376 (1940). Advertisements claim that special grades of zinc sulfide increase impact strength with little effect on cold flow. (166) S o r t o n Co., Brit. Patent 533,363 (Feb. 26, 1941). Abrasive articles. (167) Numaairi, S.,J. SOC.Chem. Ind. (Japan), 42, 319H, 369B (1939); 43, 92B (1940) ; 43, No. 9, suppl. bind., 285 (1940); Brit. Chem. Abst. (B) 630 (1940). Studies of the hard rubber reaction. (168) Nunn, D., Weston, W. R., and Standard Telephones and Cables, Ltd., Brit. Patent 528,323 (Nov. 6, 1940). Hard rubber spacers in coaxial cable. (169) Nusslein, J., and Kirst, W. (to I. G. Farbenindustrie A-G.), German Patent 729,845 (Dec. 3, 1942). Process for dyeing vulcanite goods with leuco salts of sulfuric acid esters of vat dyes. (170) Okita, T., J . SOC.Chem. Ind. (Japan), 42, 586B (1939). Sig. nificance of H2S liberation during heating of vulcanizate. (171) Osborne, J., Brit. Plastics, 16, 243 (1944). Reports discard of vulcanite for dental purposes in 1942. (172) Osenberg, W., Maschinenbau, Der Betrieb, 17, 127 (1938); Plastics (London), 8, 509 (1944). Tools for machining ebonite. (173) Overstreet, It. L. (to Salts Corp.), U. S. Patent 2,271,498 (Jan. 27, 1912). Closed cell cellular hard rubber products by releasing gas pressure after curing to soft rubber stage. (174) Owen, E. W. B., Walker, R., and H. G. Miles Ltd., Brit. Patent 543,143 (Feb. 25, 1942). Use of crushed fiber scrap as filler in manufacture of light weight protective helmets. (175) Palmer, H. F., Rubber Age (N. Y.), 47, 249 (1940); India Rubber World, 102, 53 (1940). Value of reclaim in improving processing of ebonite stocks. (176) Parker, T. C., Brit, Patents 533,757 (Mar. 5, 1941). Cigaret holders. (177) Parris, R. W., and Scott, J. R., J . Rubber Research, 10, No. 12, 123 (1941); Rubber Chem. Tech., 15, 280 (Apr. 1942). Swelling in various liquids.

October 1947


Partridge, E. G. (to B. F. Goodl.irh Co.), G . 8.Patent 2,256,408 (Sept. 15, 1941). Microporous rubber articles, such as filter or storage battery separators: apparatus and method of manufacture from a stable. flowable, latex compound, confined during vulcanization in a watertight mold. 1 i 9 i Perry, J. H., “Chemical Engineers’ Handbook,” 2nd ed., New Tork, McGraw-Hill Book Co., Inc., 1941. Zndia Rubber R’orld, 106, 181 (1942), Requirements for roller-grinders for ebonite. 1x0) Pfleumer, H., Zndia Rubber World, 105, 573, 577 (1942). Requirements of cellular rubber for use in refrigerators. l k l i Pichugina, A. A,, Znf.-Tekh. BguZZ. Glavkhimplast, No. 1-2, 81, (1940). Proposing boghead, a low grade coal, as cheap filler for ebonite from Russian S.K. rubber. 182) Plastics, 8 , 359 (1944). Diamond tools for machining. ;183) Zbid., 111. Use of expanded hard rubber in aircraft industry. 1184) Plastics Catalog Corp., “Plastics Catalog,” 1942, 184: 1943, 80; 1944, 98; 1945, 88. Brief summarized comparison of properties of hard rubber with those of other plastics. ’ 185) Quarmby, B., Brit. Plastics, 13, 376, 405, 484, 493, 545 (1942). Water absorption. 1XHi Quinn, N. G., India-Rubber J . , 105, 62 (1943); Rubber Chem. Tech., 17, 192 (1944). Controlling cure of thick samples of natural and synthetic mixes. 1 1 X i i Rainier, E. T., U. S. Patent 2,216,135 (Oct. 1, 1940); Zbid. (to U. S. Rubber), Canadian Patent 387,523 (Mar. 19, 1940). Abrasive articles from mix including anhydrous, water-soluble inorganic salt of alkali metal. ,lb8) Ratnaparkhe, A. D., Science and Culture, 7, No. 1, 55 (1941). Satisfactory ebonite from African wild rubber. (189) Rev. Gkn. caoutchouc, 17, 63 (1940). Flexible ebonite containing neoprene. $190) Itewell, H., Brit. Patent 549,442 (Dee. 2, 1942). Ebonite cigaret holders. ,191) Richardson, R. P., and Burndept, Ltd., Zbid., 558,207 (Jan. 5, 1944). Battery applications. 192) Rieser, 0 . O., U.S. Patent 2,336,423 (Dec. 7, 1943). Battery applications. ,193) Rimarski, W., and Noack, K.. Autogene Metallbearbeit, 33, 69 (1940). Causes of the burning out of pressure-reducing valves for oxygen and methods of eliminating these causes. Materials tested include 11 grades of hard rubber and 3 hard rubber substitutes. lY4) Itoberts, D., Cooper, L., and Bascom, R. C., Canadian Patent 386,504 (Jan. 23, 1940). Rubber boat fender. 195) Roberts, S. T., Brit. Patents 537,846-7 (July 23, 1941). Electroplating barrels. 196, Roelig, H., India-Rubber J., 105, 621 (1943). Satisfactory articles froin all Buna. 197) Roelig, H., Kunststofe, 30, 15 (1940). Properties of all Buna vuloanizates. 1198i Rohm & Haas G. m. b. H., Dutch Patent 50,446 (May 15, 1941); German Patent 709,886 (July 17, 1941). Method of molding objects from natural or synthetic hard rubbers involves partial vulcanization to soft rubber state, stretching, and completion of vulcanization under tension. 1Y8i Rostler, F., and Mehner, V., India Rubber World, 104, 47 (1941). Use of Naftolen to improve surface finish and resistivity. (200) Royal SOC.for Prevention of Accidents, Industrial Accident Prevention Bull., 12, 19 (1944). Unsatisfactory performance of lifting tackle wit8h ebonite coverings used in metalpickling processes. 4201) Rubber Age (London), 21, 201 (1940). Rubber-bonded cutting wheels for steel-cutting operations. !202) Zbid., 21, 284 (1940). Use of hard rubber rods in white lead manufacture. 203) Ibid., 22, 9 (1941). Need for greater heat resistance in the dyeing and bleaching industries. ‘204) Ibid., 23, 166 (1942). High yield-temperature ebonite from ilmeripol. 20a) Rubber A g e (N. Y.), 49, 104 (1941). Effect of outbreak of war on hard rubber production. ,206) Sachs, E., German Patent 615,194 (June 28, 1935): Kautschuk., 16, 11 (1940). Preserving surface finish during heating. 2 0 7 ) Saito, M., J . Electrochem. Assoc. (Japan), 8, 91 (1940). Physical, mechanical, and electrical properties compared to those of other plastics. 208) Sauter, E. (to Siemens-Schuckertwerke A.-G.), German Patent 714,125 (Oct. 30, 1941). Thermocouple for measuring temperature during heat treatment. in a high frequency field. 209) Zbid., 725,859 (Aug. 20, 1942). Use of dew point of certain liquids as indicator in temperature control during drying of vulcanite, etc. 178)

~

b

1247

(210) Schelhammer, H. J. (to American Hard fiubber Co.), tr, 9. Patent 2,214,182 (Sept. 10, 1940). Tank linings. (211) Schelhammer, H. J., and Coursen, D. H. (to American Hard Rubber Co.), U. S. Patent 2,274,260 (Feb. 24, 1942). Per-

(212)

(213) (214) (215) (216) (217) (218) (219)

12201 (221) (222) (223) (224) (225)

(226)

(227)

meable hard rubber batteiy separators, filters, etc.; process involves wet vulcanization against unglazed, unstretchable paper which is removed after drying. Schelhammer, H. J., a,nd Hunt, K. E. ( t o American Hard Rubber Co.), U. S. Patent 2,336,754 (Dec. 14, 1943). Apparatus for preparing uncured permeable h r d ruhber composition strips for vulcanization. Schwitttnann, A., Kunststoff-Tech. u . Kunststoff-Antuend., 12, 286 (1942). Critical review of impact testing methods. Scott, J. R., J . Rubber Rcwarch,, 13, 23 (1.944). Properties of Buna ebonites. Scott, J. R., J . Sci. Znd. Research (India), 3, 345, 407 (1945, Effects of shellac as compounding ingredient. Scott, J. R . , Trans. Faraday SOC.,38, 284 (1942) : India-Rubber J., 103, 374 (1942); Rubber Chem. Tech., 15, 82G34 (1942) Plastic-elastic behavior of ebonit,e. Theory. Scott, J. R., Trans. Inst. Rubber Ind., 17, 74 (1941). Crushed glass a8 a compounding ingredient. Zbid., 20, 8 (1944). Relation of rheological behavior to strncture. Sears, W. C., J . Applied Phys., 12, 35 (1941): J . Testilp Inst., 32, 189A (1941). Energy trarismlssion and absorption by rubber, etc. Theory. Sheet Metal Worker. 30, KO.8, 25--6 (1939). Finishing with rubber and other grinding wheels. Common troubles and correction. xrdschlag, K. G., U. S. Patent 2,331,612 (Oct. 12, 19431 Combination of hard and soft rubbers to form a hinge. iimonds. J. C., Plastics Resins Znd., 1, 14 (1943). Fundamentals of sawing sheets, rods, and tubes. Sinithers, V. L., U. S.Patent 2,198,845 (Apr. 30, 1940). Bat tery separators. Snelson, J. W.,Metropolitan-Vickers Gazette, 20, 175 (19433, New bridge for measuring power factor a t audiofrequencies. Societa Italiana Pirelli, Belgian Patent 433,992 [Nov. 21, 1939). Machine bearings with graphite and cotton. Brit. Patent 537,665 (July 16. 1941). Steering wheels. Zbid., 528,892 (Nov. 20,1940). Snci6t6 Anon. de Manufactures des Glaces et Products Chimiclues de Saint-Gobain, Chauny et Cirey, French Patent $45,744 (Aug. 31, 1939). Cse of starch in microporous rubber. Yoci6t6 Franco-Belge du Caoutchouc Mousse, Italian Patent 380,299 (May 4, 1940). Process for microporous hard rub-

her. (228) Soci6t6 Industrielle des Cornprimes de l’Quest, French Patent $79,200 (Nov. 10, 1942); Belgian Patent 449,119 (Nov. 2. 1943); Rm. Gkn. caoutchouc, Doc. Anal., 21, 79, 160 (1944).

Separators with premolded ribs. (229) doday, F. J., U. S. Patent 2,345,013 (Mar. 28, 1944).

TPI,I. perature control during vulcaiiization of thick articles. (230) Sorin, A., Rev. G6n. Mat. Plastiquas, 15, 236 (1939). h1:triu. facture of combs. (231) Sponge Rubber Products eo., S.A.E. Journal, 53, 106 (1945, Advertisement, cellular hard rubber for floats. (232) Standring, W.G., J . Znst. Elec. Engrs. (London), 88, 11, 36Li (1941). Influence of variables on dielectric strength !ilea,+ urenients. (233) Stock, C. It., A.S.T.M. Bull., 130, 21 (1944). Desctiptinr, of rolling ball method of impact testing. (,234) dtretton, A. T., and British Thomson-HousLon Co.. L I . ~ . , Brit. Patent 553,597 (June 9, 1943). Use to support lwatiup elements in de-icing equipment for airplane propeller.,. ( 2 3 5 ) Btriclihouser, S. I., and Uhlig, E. C., U. S. Patent 2,:142.929 (Aug. 14, 1945). Battery separators with hollow ri (236) Stuck, E., German Patent 707,659 (May 21, 1941). A for celluloid to ebonite. (237) Sweeney, W.T., and Caul, H. J., J . A m . Dental Assoc.. 127, 1446 (1940); Rubber Age (N. Y.), 48, 199 (1940). Prlnposed standard spec. for denture base materials. i288) Szper, J. A., and Varley Dry Accumulators, Ltd., Brit. I’ 537,377 (July 2, 1941). Use of glass fibers in batterjrators. Zbid., 540,591 (Nov. 5, 1941). (239) Tegner, C. E.,Ibid., 563,362 (June 2, 1943). Eboniteear ~ ~ I L I P (240) Telfair, D., and Nason, 11. K., A.S.T.M. Bull., 128, 50 (l(1-1 1 Influence of variables in impact strength tests. (2.41) Tinius Olsen Testing Machine Go., Zbid., 130 (1944). . \ & vertisement, impact testing machine of new design. (242) Tornberg, H. T., (to National Rubber Machinery Co.) G ,> Patent 2,330,319 (Scpt. 28, 1943). Apparatus for fcrmiijg and vulcanizing articles such as vehicle steering wheels of hard rubber.

1248


Shellac az a conipounding ingredient. (244) Trevaskis, H., Wright, J., and Dunlop Rubber Co., Ltd., Brit. Patent 550,101 (Jan. 6, 1943). Hard rubber wind vanes to spin wheels of large aircraft prior to landing. (245) Tupper, E. S., Ibid., 553,912 (June 23, 1943). Ebonite combs. (246) Turner, C., Ibid., 518,936 (Feb. 28, 1940). Roller coverings with a soft cushion layer. (247) United Aircraft Corp., Mech. World, 116, 364, 458 (1944). Porous ebonite cuffs for propeller blades. (245) U. S. Rubber Co., Brit. Patent 525,537 (Kov. 11, 1940). Flexible ebonite; porous hard rubber filters. (249) Ibid., 532,475 (Feb. 5 , 1941). Increasing pore size in microporous products through use of silica gel. (260) Ibid., 547,648 (Sept. 16, 1942). Static-free combs. (251) Ibid., 569,076 (May, 16, 1945) and 569,989 (June 27, 1945). Use of natural-synthetic blends in abrasive articles. (252) U. S. Rubber Co., Sci. American, 167, 28 (1942). Use of cellular hard rubber as insulation under decks of naval vessels and for supporting fuel tanks in aircraft. /253/ Ibid., 171, 227 (1944); Mech. T o d d , 116, 515 (1946). Advantages of hard rubber battery separators. (254! Van Antwerpen, F. J., IKD.ENG. CHEM.,32, 1580 (1940). Characteristics of uorous hard rubber comuared with those of other filtering media. (255) Vanderbilt Sews, 10, No. 1, 8 (1940). Fillers. (256) Ibid., 10, 90.6 , 12 (1940). Preparation of ebocite directly from latex. (257) Ibid., 11, No. 5, 4, 66 (1941). All reclaim ebonite. (258) Wakeman, R. L., Modern Plastics, 18, No. 11, 65 (1941). Dimensional effects of prolonged immersion in cold and boiling water. (243) Trans. I T L S Rubber ~. I n d . , 15, 225 (1939).

Vol. 39, No. 1C

(2.59) Walker, B. F. (to hl'etaylaat Corp.), Brit. Patent 524,819 (Aug. 28, 1940); India-Rubber J . , 100, 378 (1940); (tc Metaplast Corp.). U. S.Patent 2,303,571 (Dee. 1, 1942)

Metal-coated plastic material including hard rubber. Chromiurr boride cutting tools. \Tallace and Tiernan Products Inc., Brit. Patent 562,537 (July 19, 1944). Applications of expanded ebonite. Waring, J. R. S., Trans. Inst. Rubber Ind., 16, 23 (1940,. Method of following changed during vulcanization by measuring electrical conductivity. Washburn, L. 8. (to Norton Co.), C. 8. Patent 2,196,09(1 (Apr. 2, 1940). Rubber-bonded abrasive. Webster, D. E., Canadian Pat,ent 389,911 (July 9, 194Ui Cutting-off wheel. Wells, L. E. (to Willwd Storage Battery), T2.S. Patent 2,247,. 161 (June 24, 1941). Storage battery. Weathead, J., and United Ebonite & Lorival, Ltd., Brit Patent 564,773 (Oct. 25, 1914). Method of curing litrgc battery boxes. Winspear, G. G., Herrmann, D. B., Malm, F. S . , and Kemp 1.R., ISD. ESG. CHEM., 38, 687-94 (1946). Comparison of natural and synthetic hard rubbers. Winton, G. E., Rubber Age (N. Y . ) , 50, 363 (1942). Specia: abrasive cloth for wet use during finishing operations. Woods, S. H., and Ebonite Container Co., Ltd., Brit. Patent 523,690 (July 31, 1940). Special machinery for nianufarture of storage battery cases. Zhornitskii, I. G., Gosudarst. Inst. Prikladnoi Khim.,Sbornih Statei., 1919-39, 233-40 (1939) ; Khim. Referat. Zhur. 1940, No. 3, 97-8. Microporous ebonite from nat,iiral latex.

(260) Wall Colmonoy Corp., Plastics, 6, 191 (1942). (261) (262) (263j (264)

(266) (266) (267)

(268) (269) (270)

Stainless Steels and Other Ferrous Alloys E. 1. d u Pont de iliemours & Company, Znc., Wilmington,Del.

R

ESEARCH and development in the field of stainlebs ateels

and related alloys were greatly influenced during the war by urgent and specialized needs. Examples of such investigations aimed specifically at wartime objectives were: ( a ) the development of information t o permit the use of the high strength-toweight ratios of cold-rolled stainless steels in aircraft construction: ib) the application of austenitic stainlebs electrodes to the welding of ferritic materials, such as armor plate; (e) the wtension of basic knowledge t o allow the eld ding and application of the high chromiuni ferritic alloys in synthetic rubber process equipment; and ( d ) the development and production of alloys possessing high strength a t elevated temperatures and meeting other requirements for gas turbine service. Traluable results of the last-named investigation have been recently published but are not discussed here because most of the alloys involved are no6 within the scope of this article. There has also been considerable progrebs on some of the mole fundamental aspect5 of stainlesa steels, such as stresscorrosion cracking, the phenomenon of passivity, occurrence of sigma phase, and modifications in composition t o meet specific needs. This review deals principally with the advances made in austenitic stainle.ss steels diiring the period from the bt,ginninp of the war through 1946. YEW COMPOSITIONS

Several new eompositionP, some uf major importance, have heen developed during this period. Shortly before the war, the use of columbium-stabilized 18-8 in the chemical industry became widespread. The principal advantage to be gained through the

addition ~f this and other stabilizing elements to stainlesa -tee1 Ithe elimination of post-fabrication heat treatment without liability of service failure by intergranular attack. Columbium additions to molybdenum-bearing 18-8 seemingly should be simi. l a d y effective, but early attempts to add columbium to converrtional Type 316 and Type 317 alloys gave erratic and unsatisfar tory results. Franks, Binder, and Bishop (40) reported thai close control of composition to maintain an austenitic structurt was required in order to obtain effective stabilization, and that, ain Type 316 or Type 317, formation of sigma phase (a brittle constituent) occurred upon exposure to intermediate temperatures, ii appreciable amounts of ferrite were present. B molybdenum COIItent of approvimately 2y0 was recommended by these workers Developmmt of the alloy was retarded by the war, but limitec rommercial experience has supported the conclusion that a whollj austenitic ~ t r u c t u r eis highly desirable. The present preferred cornpodion range (in per cent by weight) is C 0.07 may., Cr 17.50-19.00, S i 13.0-14.5, MO 2.0-2.5, >In 1.50 min., Si 0.7.'~ max., Cb and 0.5CFO.90. Further extending the field of columbium-stabilized alloys, ti considerable tonnage of 25-12-CtJ (composition in per cent b~ weight C 0.07 max., Cr 22.0 min., S i 12.0 min., M n 1.25-2.5 Si 0.75 mas., C b ten times c/c C min. to lYo max.) has been employed for severe service conditions, and limited quantities of 2520-Cb have been produced. Another possibility for achieving thc same objective -that is, avoiding the necessity of heat treatment for severely corrosive service-which is under investigation ann in limited commercial use, but not yet reported in the literature. is an extra-low carbon (0.03% max.) grade of 18-8 and 18-8-1Itr

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