INDUSTRIAL A N D ENGIXE’ERING C H E M I S T R Y
1030
taining the dried residues, heating was continued until the contents were well charred, after which the dishes were cooled. Concentrated nitric acid (5 cc.) was added to each and heating was resumed until heavy fumes of sulfuric acid were evolved. The nitric acid treatment was repeated until the residues became light in color and remained so after evaporation to dryness. The dried material in each dish was completely dissolved in 8 cc. of 30 per cent sulfuric acid and 10 cc. of water.’ Qualitative tests were then made for the metals in each of the eight solutions thus obtained. Standard analytical procedure was followed. Solvent Action of o-Dichlorobenzene on Metals and M e t a l Oxides METALOR SOLVENT METALOR SOLVENT OXIDE ACTION OXIDE ACTION cu Nil Xi Faint trace CUO Appreciable NiO Appreciable Nil A1 Faint trace Appreciable AlzOa Trace
Discussion of Results The analytical tests showed that the oxides of the four metals treated are susceptible to the solvent action of odichlorobenzene. This action is more pronounced with the help of frictional rubbing. The negative tests for silver and 1
Noyes, “Qualitative Chemical Analyses,” p. 54.
Vol. 19. No. 9
copper were conclusive. The action on nickel was extremely slight. The test for metallic aluminum was not conclusive. o-Dichlorobenzene paste when used as a metal polish possesses the following merits: It contains no acid or alkali; it is not dangerous to handle nor is it inflammable at room temperatures; it does not scratch or corrode metal; it does not vaporize rapidly. It has been found that the incorporation of small quantities of aromatic oils will mask the persistent odor characteristic of o-dichlorobenzene. Table utensils treated with this polish need t o be dipped in boiling water before they are used again. I n industrial practice, metal articles may be merely dipped into a vat containing o-dichlorobenzene and then brushed briskly to produce a bright luster. The paste polish is particularly adaptable for door plates and knobs, where it performs the dual role of dissolving accumulated grease and removing tarnish. Summary Commercial o-dichlorobenzene is an excellent cleansing agent for metals. I n some industries it may be used unmodified. For domestic use it may be put up as a thin paste in bottles, or as a heavier paste in collapsible tubes or jars. I t acts as a solvent for the oxides of nickel, silver, copper, and aluminum. Its action on the metals is practically negligible.
Influence of Temperature on the Tensile Strength of Reclaimed Rubber’ By Henry F. Palmer THEX Y L O S RUBBERL O . , AKRON,OHIO
The effect of t h e temperature of the test strips and t h e surrounding atmosphere during test upon t h e resulting tensile of vulcanized reclaimed rubber mixtures is quite marked. The tensile, stress, and elongation decrease with rise in temperature. The large number of tests on whole-tire reclaim shows t h a t within normal room temperature limits of 18” to 32’ C. the relation tends t o be linear. Some variations from t h e linear relation have been observed, and may be due t o variation i n temperature rise in the strips during stressing or t o error in t h e method.
EVERAL
The percentage decrease in tensile for vulcanized reclaimed rubber mixtures with rise in temperature is appreciably greater t h a n for vulcanized new rubber mixtures, as found by other investigators, being between 16 and 24 per cent for t h e former and well under 12 per cent for the latter. I t is possible to use a correction chart for practical purposes, t h e error involvedin thecaseof t h e whole-tire reclaim studied being approximptely t h a t which may occur in a series of tests on the same vulcanized mixture a t one temperature, or *3.5 per cent when eight strips are tested.
investigators’ to have pointed out that the tensile strength of vulcanized new rubber is influenced by the temperature at which the tests are conducted. I n general they have concluded that as the temperature increases the elasticity and elongation increase and the tensile decreases, and that the tensile of low-grade rubber is influenced to a greater extent by temperature changes than that of high-grade rubber. The present investigation shows that the percentage change
in tensile strength with changes in testing temperature is more marked in the vulcanized mixture prepared from reclaimed rubber than when prepared from new rubber, although actual numerical differences are not so greatly different. This is of particular significance to the reclaimed rubber industry, since the product is often sold on a specification basis and seasonal variations in testing temperatures may result in the rejection of material in the summer months that would be quite acceptable during the winter.
1 Presented before the Division of Rubber Chemistry a t the 73rd Meeting of the American Chemical Society, Richmond, Va., April 11 t o 16, 1927. 2 Breuil, C Q O U ~ C ~ b’gulla-percha, OUC 8,5298 (1911). 8 Wormeley, “The Rubber Industry,” p. 246 (1914). 4 Buv. Standards, Circ. 88, 60, 83 (1921). 5 Nuckolls, India Rubber World, 67, 79 (1922). Report of Physical Testing Committee of Division of Rubber Chemistry, THISJOURNAL, 17, 535 (1925). 7 Boone and Newman, I b i d . , 18,539 (1926).
Conditions of Work The data recorded herein were obtained according to the standard practice recommended by the Physical Testing Committee of the Division of Rubber Chemistry.8 The stocks were mixed on an 8 by 16-inch (20 by 40-cm.) mill having a roll rat@ of 3: 2, the slow roll making 14 r. p. m. Cures were made at 141.1 C. in a platen press which was checked by means of a calibrated thermometer inserted in a special mold. Tests were made on a
S
*
‘ 9
INDUSTRIAL A Y D ENGINEERING CHEMISTRY
September, 1927
calibrated Scott machine having a jaw separation under load of 22.5 inches (57 cm.) per minute. Although the room in which tests were conducted did not have thermostatic control, when once the desired temperature had been obtained it invariably remained constant to within *0.5" C. during the period of ex-
1031
being tested for each point, check very closely and the slope of the curve obtained agrees with that obtained from the fifty test strips. These results are shown in Figure 2. The above findings have further been established for other reclaimed rubbers as given below. Solid-Tire, Tube, a n d Carcass Reclaims
Five parts of sulfur were mixed Tvith 100 parts of each reclaim and the mixture cured 25 minutes a t 141.1" C. I n the case of the carcass reclaim 1 per cent of di-o-tolylguanidine was also added. The results are given in Figure 3. The tensile and stress in each case decrease with increased temperature, as does the elongation for the solid tire and carcass reclaims. With the tube reclaim the elongation shows a slight increase from 10" to 20" C. Further tests have shown that there is a tendency for the elongation of the tube reclaim to decrease, but this decrease is not marked. Figure 1
Effect of C u r e and Process
Whole-tire reclaim Xo. 1 was cured 15, 25, and 35 minutes, ten strips being tested a t 10 ', 20 30 ', and 39 C. The results (Figure 4) show the same trend as those in Figures 1 and 2. These results, as well as other check tests (in which the 45minute cure was included), show no particular effect of cure on the curve except t o displace it, as the magnitude of the physical properties varies with the cure. Figure 4 also shows that maximum physical properties are obtained with the 25minute cure. The curves are very similar to those of Nuck011s' for a low-tensile, new-rubber mixture. O,
~
I
I
I
I
I
I
I
I
O
I
I
I
1
Figure 2 Whole-Tire R e c l a i m No. 1, 2 5 - M i n u t e Cure
posure and testing. The test strips were exposed to the temperature at which they were to be tested for a t least 2 hours, this time being sufficient for the establishment of equilibrium. The relative humidity during the tests remained between 20 and 40 per cent, being determined by a sling psychrometer. According to StringMda in the case of new rubber mixtures relative humidity changes between 40 and 60 per cent are taken care of by proper exposure. The samples of reclaimed rubber were exposed for 16 to 24 hours in the uncured state after mixing a t a room temperature of 20" to 23" C., and after curing for 20 to 24 hours at the same temperature and for a t least 2 hours within =+O.5' C. of the testing temperature. Whole-Tire Reclaim Figure 3-Solid-Tire,
I n a mixture of 100 parts of whole-tire reclaim No. 1 and 5 parts of sulfur the maximum physical properties are obtained in 25 minutes when vulcanized a t 141.1" C. This cure was chosen for the more exhaustive investigation and in order to simplify the work. The reclaim was very well blended both before and after mixing in the sulfur. Tests were conducted a t IOo, 20°, 30°, and 37.5" C., fifty test strips being broken a t each temperature. The probable error for all temperatures as calculated by the method of least squares averages *0.6 per cent from the tensile given by the arithmetical mean. The results (Figure 1) show that the effect of temperature on tensile here is best represented linearly up to about 32" C., where with increased temperature the tensile appears to tend toward a minimum value. The stress a t 300 per cent elongation also decreases with increased temperatures, but to a lesser degree than tensile. The elongation decreases with increased temperature, whereas with new rubber mixtures* to 7 s .'nI it has been found to increase. Subsequent tests on three different samples of the same stock tested at 4 O , 5.5", 1 3 . 5 O , 19.5", 27", and 27.5" C., eight strips 8
THISJ O U R N A L , 17, 833 (1925).
Tube, a n d Carcass R e c l a i m s
Two other whole-tire reclaims, Nos. 2 and 3, which were processed on different factory equipment, were tested. Five parts of sulfur were mixed with 100 parts of each of the reclaims and the mixture cured 25 minutes. Ten strips were tested a t 5.5", 20", 30°, and 37" C., with the results shown in Figure 5. The effect of temperature on tensile does not appear to be modified by the type of process. Discussion of Results
It has been observed that the points do not always fall on a straight line, especially when fewer strips were tested. Further tests on carcass and tube reclaims showed a slight dip in the curves a t 20" C. These irregularities may be due to a temperature variation during stressing, as described by Boone and NewmanJ7 or to error in the tests, which is *3.5 to 4.0 per cent for eight to ten test strips. The data show that as the temperature increases from 20° to 30" C. the tensile of whole-tire reclaim No. 1 (25-minute cure) decreases approximately 21 per cent. The drop in tensile in this same range for the 15- and 35-minute cures of
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
1032
whole-tire reclaim No. 1, 25-minute cures of whole-tire reclaims Nos. 2 and 3, solid-tire, tube, and carcass reclaims as shown in the curves, ranges between 16 and 24 per cent. The percentage decrease in tensile for vulcanized new rubber to 30" C. appears t o be well under m i x t ~ r e from s ~ ~ 20' ~~~ 12 per cent. While the numerical magnitude of the decrease in tensile of reclaimed rubber with increase in testing tem-
Vol. 19, No. 9
Table I gives eleven tests on different samples of wholetire reclaim No. 1 in which eight strips were tested a t 20", 30.5", and 31.5"C. The figures obtained a t 30.5" and 31.5" C. were referred back to 20' C. on the chart and the figure thus obtained was compared with that of the actual test. The error averages less than 5 per cent, the maximum noted being 7.3 per cent. S t r e n g t h of Whole-Tire Reclaim No. 1-25-Mlnute Cure TEMOBFROM FIG- DEVIA-
Table I-Tensile W
TEST
PRRATURE
C.
co
A B
0 50
5 \ 45
C
$10
35
D
E F G
Figure 4-15,
25-, 35-Minute Cures, Whole-Tire Reclaim No. 1
H
20 30.5
Diff.
20 30.5
Diff.
20 30.5
Diff.
20 30.5
Diff.
20 30.5 Diff. 20 30.5
Diff.
20 30.5
Diff.
20 30.5
Diff.
SERVED
Kg./sq. cm. 51.0 40.1 10.9 48 9 41.5 7.4 48.2 39.4 8.8 46.4 34.4 12.0 47.1 37.3 9.8 47.1 37.6 9.5 49.9 38.0 11.9 46.7 36.9 9.8 70.7 57.3 13.4 66.0
URE 6 K g . / s q . cm. 51 3
TION
K g . / s q . cm.
ERROR
Per cent
+0,3
+0.6
52 5
13.6
+7.3
50 5
+2.3
+4
45 4
-1.0
-2.2
48 5
+1.4
~ 3 . 1
48.7
t1.6
+3.4
49 3
-0.7
-1.4
48 2
+1.4
t 3 0
8
perature is in many cases no greater or as great as that for Ia 20 +2.3 68 2 +3 3 31.5 vulcanized new rubber mixtures, the percentage change is Diff. 20 0 65 0 0.0 J" much greater as vulcanized reclaimed rubber has in general 31.6 541 a much lower tensile strength. It has been rec0mmended4~Q Diff. 10.9 K5 20 -1.2 -1.7 69.9 68 7 that tests on rubber goods be conducted a t a room temper31.5 57.6 Diff. 12.3 ature between 65" and 90" F. (18.4" to 32.2" '2.). It is quite a High-tensile No. 1. evident that such a range is too wide for testing reclaimed rubber a t least. It seems desirable that a standard testing The error in testing this reclaim has been found to be apor reference temperature between 70" and 75" F. (21.1' and proximately *3.5 per cent when eight test strips are used. 23.9" C.) be agreed upon. This method of compensation is therefore quite applicable Compensation for T e m p e r a t u r e Effect and, although it has not been tested thoroughly in other cases, gives indicaI n order to have comparable tensiles on a given reclaimed tions of being satis7o rubber a t all times either the vulcanized mixture must be factory for prac- s6s tested in a constant temperature room or a method of com- tical purposes. It pensating for the difference in tensile caused by temperature is sufficiently ac- ysI changes must be used. The applicability of the second alter- curate as a control 9 check, but where several reclaimed''2 rubbers are t o be studied a t various 3f; F *s times it would be JO yo.. i n c o n v e n i e n t to /O /2 I t /6 /B 20 12 d# 26 28 JO 82 TzYP.qqn/&r T. 2 4s determine t h e Figure 6-Correction Curves for Whole-Tire specific correction &a Reclaim No. 1 curve for each one. % . For such work a constant-temperature room is desirable. JO Possibly humidity control should be combined with temperature control, though the magnitude of the effect of humidity changes on the tensile of reclaims has not been published.
GS0
50
Figure 5-Whole-Tire Reclaims Nos. 2 a n d 3, 25-Minute Cure
n a t k e has been tried out quite thoroughly in the case of wholetire reclaim No. 1. For this purpose Figure 6 was used, in which a series of straight lines has been drawn parallel to the tensile curves shown in Figures 1 and 2. By means of this chart tensiles obtained a t any temperature within the limits given may be referred to any desirable reference temperature. @
Bur. Standards, CirC. IS2, 6 (1925).
Discussion Q. Was any sample, after exposure to higher temperature, dropped back again to a lower temperature and tested to eliminate any possible effect of post-vulcanization? A. No, not exactly that. The effect of overcure on the general slope of the curve appears small, from the data given on 15-, 25-, and 35-minute cures of whole-tire reclaim No. 1. In another test a 45-minute cure was also made. Further, strips held at the warmer temperatures 2 to 3 hours were found to give results which checked with those of strips held a t the warmer temperatures for 10 to 12 hours.
September, 1927
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Q. Do the curves on freshly made reclaimed rubber follow the same general trend as that which has been developed? A . I think that they would. The tests given were on reclaims a t least one day old. The magnitude of the tensile for more freshly made stock-that is, say one hour old--is less, but I would expect a similar effect of temperature changes. Q . Do you consider reclaim one day old as good as one, say, a week or 2 weeks old? A. That depends on how you measure the “goodness” of it. The tensile of a stock one day old is not vastly different from that of a stock a month old. Q. Is there a displacement of the stress-strain curve or is it merely shortened? A. There would be a slight displacement of the entire stressstrain curve toward the strain axis as the temperature rises.
1033
Q. Will an overcured stock follow the same curve in tensile strength as undercured stock? A. I gave the three cures 15, 25, and 35 minutes. The longest cure made on the whole-tire reclaim was 45 minutes, but up to 45 minutes there was no change in the general slope of the curve, so it would be my conclusion that the effect of temperature on tensile would be the same with the different cures, the curves being displaced as the magnitude of the tensile changes with the degree of cure. Q . Would the same curve obtain on reclaims mixed with rubber definitely proportioned to rubber, say one-third to onehalf? A. It would be the same type of curve but have a different slope. Note-The
answers in this discussion are by the author in each case.
New Chemical Reactions of Rubber Hydrocarbons‘ Reactions with Metallic Halides By H. A. Bruson, L. B. Sebrell, a n d W. C. Calvert THEGOODYEAR TIRE8- RUBBERCOMPANY, AKRON,OHIO
I
T HAS been o b s e r v e d
The rubber hydrocarbon a d d s the halide salts of t i n , many classes of organic cornthat unsaturated hydroiron, a n t i m o n y , a n d t i t a n i u m to f o r m colored addition pounds that contain an unc o m p o u n d s . A s t a b l e addition p r o d u c t w i t h SnC14 has carbons, such as isoprene, saturated atom or a double cyclopentadiene, and indene, been isolated a n d possesses t h e f o r m u l a (C6H8)10.SnC14. bond.3 when treated with the halide Elimination of t h e SnCI4 by alcohol gives a polymer of The addition of SnCl, to salts of tin, iron, antimony, rubber. Two s u c h isomeric p r o d u c t s have been obrubber hydrocarbon occurs a t titanium, boron, and arsenic, t a i n e d f r o m Hevea r u b b e r which f u r n i s h additional the most reactive point in the evidence of its two-phase n a t u r e . T h e a c t i o n of halide molecule. A c c o r d i n g t o u n d e r g o polymerization to yield compounds of appars a l t s on balata, isoprene, a n d polymerized isoprene is Staudinger’s theory of end described. v a l e n c e s , 4 addition of the ently high molecular weight.2 S u c h polymerized products halide salt should take place are white amorphous powders. The halide salt first forms a t the ends of the hydrocarbon chain. Since SnC14 possesses a colored addition product, after which an exothermal polym- two reactive secondary valences, it is probable that two erization occurs a t room temperature. By treatment with molecules of rubber hydrocarbon add to the SnClr in such rllcohol the addition product is decomposed, quantitatively a manner that upon subsequent treatment with alcohol some liberating the polymerized hydrocarbon component. of the double bonds of the hydrocarbon bridge across to It seemed probable, therefore, that rubber, gutta-percha, form rings in the more reactive positions of the double moleor balata hydrocarbons, when treated analogously, would cule, leaving other unsaturated bonds intact. This would react in a similar manner to yield first an addition product explain the decreased unsaturation. Isoprene and balata and then a polymeride. This has been found to be the case. would be expected to behave similarly, but would, of course, yield different polymers. The mechanism of the reaction F o r m a t i o n of Additive C o m p o u n d s with rubber mav be formulated as follows: When rubber solutions were treated CH3 CH3 CHI with anhydrous SnC14, a t room temper- - - - CHz-C=CH-CH-(CH-C=CH-CH~)z-CH-&=CH-CH~I I -Rubber ature in an inert nitrogen atmosphere, +SnCli chemical addition occurred with the forCH3 CHI CHI ~:H~~=CH-CH-(CH-C!=CH-CHz).-CHr-C=CH-~Hz I mation of a colored compound. The addiRubber-SnCh * addition product tion product was fairly stable in dry nitrogen, but readily split off the metallic s:(’*‘ SnClr halide when t,reated with alcohol or C!Hz--C=CH--CH-((CHz--CCH--CH2) =,-CH~-C=CH-CHZ I I I acetone. The SnClr-rubberaddition prodCH3 CH3 CH3 *Alcohol uct possessed the empirical composition C H3 CHI CHI (CsHa)lo.SnC14. Upon treatment w i t h CH-C-CH--CH~(CH~d-CH-CH~).-CH~C-CH-CH~ I I -Rubber polymer alcohol the SnC14 split off, simultane- - - I I I 1 I 1 OUSly precipitating the h y d r O C a r b On - - - CH-C-CH-CH-(CH-C-CH-CHZ)~-CH-C-CH-CH~ -I I I ( C ~ H Bas) ~a white amorphous powder. CH3 CHI CH3 TiC14, FeCls, and SbC15 reacted in a similar way. Since TiCI4 also possesses two secondary valences it should Each of these halides possesses so-called “‘secondary” be expected to give a polymer similar to that obtained from valences of the Werner type, which enable it to add to SnC14. On the other hand, FeC13, with three secondary 1 Received June 3, 1927. For a preliminary report of some of this work valences, and SbC16, with one secondary valence, should see Dinsmore, THISJOURKAL, 18, 1140 (1926). 3 A comprehensive survey is given by Pfeiffer, “Organische Molekulver2 Bruson and Staudinger, THISJOURNAL, 18, 381 (1926); Staudinger and Bruson, A n n . , 447, 110 (1926); Bruson, Dissertation, Zurich, E. T. H., bindungen,” F. Enke, Stuttgart, 1922. 1925. 4 Ber., 87, 1203 (1924); Kaufschuk, August, 1925, p. 5.
