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20 and 22 cents per pound in 1912 and 1913. With the outbreak of the TVorld-War prices sky-rocketed to $1.31 per pound in 1916. From 1917 to 1920, inclusive, they were more stabilized and ranged from 55 to 67 cents per pound. Within the next two years prices dropped to a post-war low level of 15 and 17 cents per pound in 1922 and 1923. I n 1924 they again started on an upward swing which has continued through 1925, when the average price was about 41 cents per pound. Present prices are between 39 and 43 cents per pound, depending on size of purchases. The accompanying chart shows the average price of bromine for the five year period, 1901-1905, and for each succeeding year through 1925.
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Future Market Conditions
There is no occasion to fear that prices for bromine in the near future will reach the high level that existed during the war. So far as can be seen now, any scarcity for bromine that may arise will result from unexpected demands for leaded gasoline. Such a shortage must be temporary, in view of the large potential world resources and especially in view of the possibility of the recovery of bromine from sea water and of greatly increased production from German potash works. The bromine ship of the Ethyl Gasoline Corporation should prove to be a factor of great importance and should exert a stabilizing influence on the domestic bromine market.
Effects of Accelerated Aging upon Some Physical Properties of Hard Rubber Compounds' By E. 0. Dieterich and Harold Gray THEB. F. GOODRICH Co., AKRON,OHIO
HE meager literature
three, the most positive data A study of the impact strength of hard rubber comare furnished by the impact covering hard rubber pounds affords a simple, positive means of measuring strength, and this property contains very l i t t l e changes due to aging. Up to 14 days, aging at 158' F. concerning aging; the scathas largely guided the auproduces relatively small changes in the physical thors' conclusions. So far we tered references deal chiefly properties of hard rubber compounds. At 300' F. have been unable to obtain with the influence of expothe deterioration is rapid and very great. sufficiently detailed chemical sure to light upon surface disCompounds receiving the optimum cure are less and microscopical evidence coloration, and upon the deaffected than undercured compounds. The effect for publication. crease in the electrical resisof accelerators and age retarders on the aging curve tivity due to the formation of is not marked, so far as this investigation goes. The Methods of Testing c o n d u c t i n g films. Where percentage change in heavily loaded stocks is less than h a r d r u b b e r is used as a in pure rubber-sulfur compounds. The effect of I M P A C T STRENGTH-The s t r u c t ' u r a l m a t e r i a l , and aging is not an overcure, as the percentage of free samples are rectangular bars mechanical strength is imsulfur remains constant. 3 inches by inch by "18 to portant, it is desirable to know l/4 inch, generally milled to what may be expected of this material from the point of view of permanence of physical size from the cured sheet. The test pieces, after cooling in characteristics. Furthermore, i t is reasonable to anticipate cracked ice to 32' F. for a t least one hour, are mounted that a comprehensive study of the changes induced in hard on supports 21/2 inches apart in a n impact testing machine rubber by the agency of heat, for example, may lead to in- of the pendulum type, with the smallest dimension in the formation of value in the formulation of a satisfactory con- direction of travel of the pendulum. The pendulum carries ception of vulcanization. The data given in this paper, al- a rounded knife edge on its striking face and is arranged to though necessarily incomplete, present some new information deliver the impact to the sample midway between the supports. From the difference in the energy of the pendulum and indicate a method of attack for future study. I n the case of soft rubber compounds the stress-strain curve on release and that after impact, the impact strength of the has been found of immense value in following the changes compound, expressed in work units per unit area of cross which occur on aging. Obviously, the same criterion cannot section, is computed. Each result is the mean of three tests. TRANSVERSE SmENGTH-The test pieces are of the same so easily be applied in the study of hard rubber, since here we are generally dealing with much smaller elongations and dimensions as for the preceding test. The sample is mounted relatively high stresses. Both factors contribute to a de- as a simple beam on knife edges 2 inches apart, and loaded crease in the accuracy of measurement. Moreover, the time by a calibrated spring attached to a third knife edge midway factor involved in the preparation and testing of samples between the supports. Prom the breaking load the transand the uncertain interpretation of the results make this verse strength is calculated by the formula for the rupture of a simple beam. Three tests are made for each value given method of doubtful value. We have the choice of about a dozen different physical in the tables. SOFTENING TEMPERATURE-The test piece, also Of the of characteristics, mechanical, thermal, and electrical-all which have been more or less thoroughly investigated in re- same dimensions as the preceding one, is mounted as a simple lation to this question. Of these, three show most promise beam on knife edges 2 inches apart, and loaded at the center of yielding intelligible data-namely, impact strength, with a dead load attached to a third knife edge, the apparatus transverse strength, and softening temperature. Of the being inclosed in an electric oven. The temperature is raised uniformly at the rate of about 2' F. per minute, and 1 Presented before the joint meeting of the Division of Rubber Chemdeflections of the center are read at intervals, by means of istry and the Akron Section of the American Chemical Society, Akron, a reading telescope, until excessive deflection has taken place. Ohio, February 22 and 23, 1928.
T
ILVDUXTRIAL ALVD ENGINEERI,VG CHE,VISTRY
April, 1926
A temperature-deflection curve is then plotted (Figure I), which consists of three distinct portions: (1) a nearly linear region, ( 2 ) a portion in which the deflection increases more rapidly than the temperature, and (3) a second linear region in vhich excessive flow takes place. The softening temperature is determined from this curve in a purely arbitrary manncr. The tangent to the curve in the region of excessive flow is drawn, and the intersection of the tangent with the temperature axis is taken as the softening temperature. 0;rooH
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years before definite changes are detectable. At elevated temperatures, however, conditions are different, as evidenced by the data in the succeeding tables. Up to 14 days the effect a t 158' F. is, in general, to raise the softening temperature and the transverse strength while the impact strength decreases; that is, the stocks become stiffer but more brittle. At 300" F. the effect is much more marked, and deterioration in all three of these characteristics sets in rapidly. T a b l e I-Percentage C o m p o s i t i o n of Stocks A B D E F G H K Rubber 7 0 . 0 7 0 . 4 2 22.19 70.42 71.43 52.79 35.21 52.79 Sulfur 2 8 . 0 28.17 13.86 28.17 28.57 21.15 14.08 21.15 Clay . . . . . . 44.95 25.00 50.00 Antimony sulfide ... 5.20 25.00 Accelerator B B . . . i:4i 6.93= i:66 1.06 Accelerator DPG . . . . . . . . . 1.41 . . . . . . . . . . . . Accelerator A 2.1 Ager 6.93 . . . . . . . . . . . . . . . a 10 per cent master batch.
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TEMPLRbTURE
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The o r d i n a t e a t 1his point intersects the temperature-deflection curve in thtl region in which excessive flow commences. The load on the test piece is adjusted to give a maximum fiber stress of 2500 pounds per square inch. This is extremely high, but allows the determination of the softening temperature in a reasonably short time. It, is important that the thickness of the samples be kept within rather narrow limits on account of the dependence of the rate of rise of temperature within the test piece on the cross-sectional area. AGrw-Tlie samples are subjected to accelerated aging a t 158' F. in the Geer ovens, and a t 300' F. in a well-ventilated electric oven. At 158' F.aging is continued for 7 and 14 days. At 300" F.the procedure consists in heating the samples for 5 hours on successive days, allowing them to cool for the remainder of the 24 hours, until a maximum of 60 hours has been reached.
Table I1 shows the results obtained for rubber-sulfur niixes containing various accelerators and age retarders that have been found of value in soft rubber stocks. It is not possible to distinguish any certain effect of the accelerators in changing the course of the aging curves, as the percentage changes in impact and transverse strength are roughly equal for the different compounds. T a b l e 11-Effect of Aging on R u b b e r - S u l f u r Mixes ---AGING RECORD-Softening Impact Transverse Tem erature temperature strength strength Time g F. ' F. In.-lbs./sq. in. Lbs./sq. i n . Compound , i . Cure: 3 hours' rise, 12 hours at 300° F . Steam 167 205 12,500 Original 7 days 15s 165 147 11,300 i s 162 152 13,000 14 days 300 165 90 13,100 5 hours 300 165 142 12,800 10 hours 300 171 74 13,800 15 hours 300 161 26 13,600 25 hours 300 158 19 4 0 hours 300 142 7 6,800 60 hours Compound B. Cure: 3 hours' rise, 12 hours at 300' F . Sfeam 169 168 12,700 Original 178 19s 14,400 7 days 158 178 145 14 600 14 days 158 173 134 13:900 5 hours 300 177 81 16,300 10 hours 300 179 102 13,200 15 hours 300 155 50 9,800 23 hours 300 300 40 hours 167 21 8,100 152 2 4,900 60 hours 300 Compound E . Cure: 3 hours' rise, 12 hours at 300' P . Steam Original 267 121 7 days 158 170 14 days 158 61 5 hours 300 109 10 hours 300 15 hours 75 300 40 25 hours 300 22 40 hours 300 13 60 hours 300 Compound F . Cure: 3 hours' rise. 12 hours at 300' F. Steam Original 172 230 12.200 7 days 158 197 231 14,800 14 days 158 196 144 14,900 5 hours 300 173 107 14,000 25 hours 300 181 36 14.100 300 13 6;900 60 hours
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Results
The compositions of a few of the stocks investigated are given in Table I, and cover the range from pure rubbersulfur mixes to heavily compounded stocks. From the results obtained to date, hard rubber may be considered relatively permanent in its physical properties a t room temperature, as the indications are that it will be
For heavily loaded stocks the effect of aging is not so pronounced (Table 111). With increase in the percentage of fillers the impact strength drops rapidly, but deterioration at high temperatures is less marked. Figure 2 shows the curves obtained for three stocks of different composition. For the minimum a t 5 to 10 hours a t 300" I?. no satisfactory explanation has been found. The effect of cure on the aging curve is very pronounced in compounds containing no fillers. I n Table IV are given comparisons of two cures on two stocks. Both a t 158' F. and a t 300" F. the undercured stock shows a greater percentage drop in the impact strength than the stock which has received the optimum cure.
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T a b l e 111-Effect of Aging on Heavily Loaded S t o c k s PAGING RZCORDSoftening Impact Transverse Temg%ature temperature strength strength Time O F. In.-lbs./sq. in. Lbs./sq. in. Compound G . Cure: 3 hours' rise, 12 hours at 300' P . Steam 0rig in a I 181 89 13 600 7 days 158 195 61 14:400 158 195 14 days 74 14,200 187 5 hours 61 14,300 300 10 hours 190 64 14,300 300 15 hours 33 14 100 300 187 30 300 25 hours 189 9'200 23 300 8:500 40 hours 168 10 300 7,800 60 hours 150 Compound K . Cure: I hour rise, 4 hours at 300' P . Press 0rig in a I 201 85 13,800 7 days 158 202 67 16,100 14 days 209 63 15,000 158 202 41 300 5 hours 10,800 195 25 hours 26 300 13,000 190 19 300 60 hours 6.600 Combound D. Cure: 1 hour rise, 4 hours at 300' P . Steam Original 181 21 7,500 5 hours 187 14 300 8 800 10 hours 176 300 10 9'100 15 hours 300 185 14 8'400 25 hours 300 170 15 9'000 60 hours 300 185 10 7:600
--AGING Time Original 7 days 14 days 5 hours 10 hours 15 hours 25 hours 40 hours 60 hours
T a b l e IV-Effect of C u r e (Figures in inch-pounds per square inch) -COMPOUND B-COMPOUND E3 hours' 3 hours' 1 hour rise, 1 hour rise, rise 20 hours rise, 12 hours RECORD-4 hot& a t 270' F. 2 hours a t 300' F. Temgerature a t 270' F. Open a t 300' F. Open F. Press steam Press steam 4ni 267 258 185 ._55 158 183 140 142 43 158 130 44 300 110 53 61 300 150 109 300 90 75 300 59 29 30 40 300 24 .. 22 300 8 17 8 13
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I n general. the effect of intermittent heating is greater than chat of 'continuous heating for the same total time, as demonstrated by the data in Table V. The 60 hours of intermittent heating were divided into twelve 5-hour periods with 19 hours of cooling to room temperature between successive heatings.
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of Intermittent Heating IMPACT STESNGTH (IN.-LBs./SQ.IN.) 60 hours 60 hours a t 300° F. a t 300° F. Intermittent Continuoun heating heating CURB Compound A 3 hours' rise 2 hours at 300" F Steam) 15 9 3 hours' rise: 12 hours a t 300' F: [Steam) 7 13 Combound B 1 hour rise 4 hours a t 270' F. (Press) 8 18 6 1 hour rise' 4 hours a t 300' F. Press) 20 1 hour rise: 8 hours a t 270" F. {Steam) 13 13 3 hours' rise, 12 hours a t 270' F. (Steam) 17 18 3 hours rise, 12 hours a t 300' F. (Steam) 2 28 3 hours' rise, 20 hours a t 270' F. (Steam) 17 26 1 hour rise, 2 hours a t 270' F. (Steam) 3 1s 3 hours' rise. 2 hours a t 300' F. (Steam) 14 21 Compound E 1 hour rise, 2 hours a t 300' F. (Press) 8 13 7 1 hour rise, 4 hours a t 300' F. (Press) 15 3 hours' rise, 12 hours a t 300' F. (Steam) 20 13 Compound P 3 hours' rise, 12 hours a t 300' F. (Steam) 13 32 Compound G 1 hour rise 2 hours a t 300' F. (Press) 46 32 1 hour rise: 4 hours a t 300" F. (Press) 44 41 3 hours' rise 2 hours a t 300' F. (Steam) 10 12 3 hours' rise: 12 hours a t 300" F. (Steam) 10 7 Compound H 3 hours' rise, 12 hours a t 300' F. (Steam) 10 12 T a b l e V-Effect
The results in Table VI indicate that the deterioration a t high temperatures is not due to progressive vulcanization since the free-sulfur content remains constant within the limits of experimental error. The evidence of these experiments indicates a definite weakening of the internal forces existing within the hard rubber structure. T a b l e VI Compound B. Cure: 6 hours' rise, 20 hours a1 300' P. Hol Waler Number of hoursat 300'F. 0 5 10 15 20 25 60 Impact strength, inchpounds per square inch 144 139 68 47 21 33 12 0 . 4 2 0 . 4 4 0.45 0 . 4 4 0 . 4 3 0 . 4 4 0 . 3 9 3ooo F. Hot F r e e ~ ~ ~ ~ ~ ~ ~hours, t C rise, u r2oe hours : Number of hours at 3000 F. 15 20 25 60 Impact strength, inchpoundspersquareinch 18 22 11 12 16 9 12 Free sulfur, per cent 0 . 3 7 0 . 3 7 0 . 3 8 0.40 0 . 3 8 0.36 0 . 4 0
The Chemical Industries in America Under this title Peter N. Peters, a specialist in chemical securities and the head of the New York firm bearing his name, has issued an interesting discussion of the chemical industry, which he describes as perhaps the least appreciated of American industries. From the statistics presented we learn that fourteen chemical industries had an output worth $2,090,000,000 in 1919, $5,530,000,000 in 1921, and $7,536,000,000 in 1923. After discussing the place of chemistry in industry and civilization and noting the post-war progress, Mr. Peters has presented in tabloid form information concerning such chemical industries as the manufacture of acids, alcohol, alkalies, aluminium, cement, drugs, explosives, fertilizers, glass, leather. paints, paper, rayon, soap, and solid fats, indicating something of the importance of each and in some cases the ultimate use of the chemical product. We learn from this specialist in investment something of the attitude of the layman toward investments in the chemical industry. "While other younger and less important basic industries have rapidly passed the usual stages of private financing, public participation, and consolidation, the chemical industry-from the investment standpoint-is still not very far removed from the pioneering stage." While America is famous for her enormous industrial organizations, there are only one or two in the chemical field which can be compared in scope and activities, and indeed in strength, with their largest European competitor. Chemists have been stressing for some time the fact that most bankers know very little about chemistry, and that chemical manufacturers in the past have been unduly reticent regarding their business, having made public few complete financial statements which would help to change the attitude of the public investor. The market career of such industrial securities as have been offered
could scarcely be expected to excite public interest, for until recently most of them have been dormant. Even the stock market boom of 1925 failed to mark them up as rapidly as other stocks have advanced in price. This may be accounted for by the lack of public following, which eliminated chemical stocks from speculation. Recently, however, the public attitude has undergone a marked change. It is one of the possible fruits of the persistent effort to take to the public the story of chemistry in a form which it can understand. This interesting account of the chemicaI industries of America by a financial'man concludes with a discussion of pending developments, treating particularly synthetic ammonia, synthetic methanol, and the possibility of other commercial syntheses. A note is made of the military importance of chemistry, the stock market trend, and the advantages which come to those who do pioneer in the field of applied chemistry. As for the present outlook, Mr. Peters says: Stimulated by the new developments and by the constantly growing demand for their products, the chemical industries i n America are beginning to hum. T h e inefficiently operated companies, which t o the last moment preferred to cling t o the antiquated manufacturing processes, have been summarily wiped out during the post-war depression. The only producers who could weather the slump were those who were fitted best for economical operation. Hence, it is only natural t h a t with the increased demand, the survivors-geared t o highly competitive production a t low costs-are now disposing of their output a t a fairly satisfactory margin of profit. The wave of prosperity has already covered many a branch of the chemical industries: i t is constantly spreading, and there are reasons to believe t h a t this time the period of prosperity will be of more permanent nature t h a n ever before. T h e chemical industries are beginning t o come into their own-apparently, the chemical boom is already in the making.
