November, 1933
INDUSTRIAL AND ENGINEERING CHEMISTRY
1211
01: TENSILEPROPERTIES OF NATURAL AND METHYLRUBBER TABLE111. EFFECTOF TEMPERATURE
20'
--AT
RUBBER
STOCK
Natural Gum Natural Carbon black Methyl (heat polymer) Gum Methyl (cold polymer) Gum Methvl (cold . uolumer) Carbon black . a This cure was 30 minutes at llOo C.
CURE Min. / C. 20 30 40 60 40 b This cure was
110 110 110 110 110 40 minutes
Taaa
TB
18.6 48.0 19.2
285 347 28.2 77.6 153
.. ..
c.-
5'
-AT
EB
Tam
694 649 509 293a 278
22.3 72.2 33.1 36.0
..
TB
c.-
272 350 181 64 138
EB 622 593 516 393 230
-----AT
Tsm 17.1 38.7 8.1 6.8
..
37'
TB
c.-
219 285 14.8 13.2 55.0
EB 712 668 360 317 230)
a t 110" C.
5. The elastic properties of vulcanizates from methyl rubber were much more sensitive to change of temperature than in the case of natural rubber. The heat polymer was particularly sensitive to fall of temperature. Reduction in the temperature of the rubber (gum stock) from 20" to 5" C. increased its tensile strength from 28.2 to 181 kg. per sq. cm. with no reduction in the extensibility. The cold polymer on the other hand, while not markedly affected by a fall in temperature to 5' C., was very sensitive to rise of temperature; increase of temperature from 20" to 37" C. reduced the tensile strength of the gum stock from 68.4 to 10.9 kg. per sq. cm. Natural rubber, on the other hand, showed little stiffening when the temperature was reduced to 5" C. and relatively little softening when it was raised to 37", the figures for the tensile strength of the gum stock a t 20°, 5 O , and 37" being 282, 272, and 219 kg. per sq. cm., respectively. Even a t 70" the natural rubber retained a substantial amount of its tensile strength, whereas the strength of methyl rubber had almost vanished.
Although, as just pointed out, rise in temperature seriously reduced the tensile strength of methyl rubber, it improved its nerve and caused the rubber to retract from moderate extension without the sluggishness which characterized it a t ordinary temperature. The above statements concerning the tensile properties of methyl rubber are exemplified by the data of Tables I1 and 111. Not the full series of cures made but only the optimum cures (Table 11)or typical cures (Table 111) are quoted. Some experiments bearing on the use of elasticators were included. To a stock made from the cold polymer heavily loaded with carbon black were added 5 and 10 parts of an elasticator in the shape of a cellulose ester plasticizer (methylcyclohexyladipate). The effect was to increase the softness and extensibility of the vulcanizates and the speed of retraction, but the improvement in those respects was only moderate and left the product still far inferior to natural rubber. RECEIVEDMay 18, 1933.
(This paper will be concluded in the December, 1933, issue
Of I N D U S T R I A L AND
ENGINEERING CHEMIBTRY.)
Chlorinated Paraffin I. Relation of Chlorine Content to Physical Properties F. T. GARDNER,University of Tulsa, Tulsa, Okla.
0
Some physical properties have been determined light yellow to a deep ~mame1 CCASIONAL mention is for a series o,f samples, prepared by chlorination color with increasing c h l o r i n e m a d e of c h l o r i n a t e d parafin in the literature content. The chlorine content of commerciul parafin at 70' C., varying in (1-3), but correlated data on the of the series ranged from 2o to p h y s i c a l p r o p e r t i e s of the chlorine content f r o m 20 to 48.5 per cent cl* 40.5 per cent by weight. products of chlorination of comIntroduction of more than 40 per cent chlorine is The analyses reveal that it beaccomplished with increasing dificulty. Viscomes increasingly difficult to mercial paraffin are not availcosities of the samples ascend quite sharply after introduce further chlorine after able. S a m p l e s of chlorinated paraffin were necessary as startabout 40 per cent by weight of more than 40 per cent of chlorine is introduced. ing materials in work planned chlorine has been incorporated by the writer. Some physical POlymeriZatiOn, as a secondary process following in the paraffin. chlorination, occurs to a limited extent, if at all. The densities of the samples properties have been determined were determined pycnometrif o r a n u m b e r of samples of varying chlorine content. c a l l y a t 37.8" a n d 100" C. A series of chlorinated paraffin samples was prepared by (212" F.). The results obtained are shown in Figure 1. bubbling dry chlorine through commercial parafin, mainThe viscosities of the samples were determined a t 37.8" tained a t a temperature of 70" C. (*3O). The paraffin and 100" C. TWOcapillary tube viscometers were employed. employed had a melting point of 55.6" C. (132" F.), and an One viscometer having a small orifice was used for samples average molecular weight of 403 (cryoscopically determined which were fairly fluid. The second was employed for more in naphthalene). No catalyst was employed in the chlorina- viscous materials. The viscometers were mounted in an air tion. TFenty grams of paraffin were used in each run. bath constructed from a glass tube 2.50 cm. in diameter. The freshly prepared samples mere stored in a desiccator The air bath was immersed in a water bath. Each viscometer was calibrated against four oils of known over soda-lime for a number of days before using in order to remove hydrochloric acid. Saybolt viscosity. The kinematic viscosity of the oils was The chlorine content of the resulting samples was deter- calculated from the equation: mined by the lime method (6). Samples containing 15 per cent chlorine or less were partially solid a t 37.8" C. (100" F.) Vr = 0.22t - 180 t and were not studied further. A series of seven samples was taken for further study. The color of these varied from where t = Saybolt Universal viscosity '
INDUSTRIAL AND ENGINEERING CHEMISTRY
1212
I
30 CL C O N T F N T
I
I
I
20
50
40 1% BY
Vol. 25, No. 11
WFIGHT)
FIGURE 1. RE1,ATION OF CHLORINE COXTEXTAND DEKSITY
-00.1
zo
CL CONTEXT /%BY
40
50
WEIGHT)
FIGURE 3. RELATIONOF CHLORINE CONTENTAND CONGEALING POINT
FIGURE2. RELATIOSOF CHLORINE The calibration curves plotted on longCONTENTAND VISCOSITY Employing this equation, the moleculog scale were straight lines. lar weights of several samples have been The absolute viscosities obtained for calculated; they have also been deterthe samples are plotted on semilog scale mined cryoscopically in naphthalene as 51 in Figure 2. The three largest values solvent. shown for the 37.8” C. curve were obThe agreement between experimental tained using an extrapolation of the values and calculations is shown: calibration c u r v e for the viscometer used, and are thus subject to the possiSAMPLE 1 2 3 Mol. C1 content wt. (from C1 content) 501.5 20.21653.0 29.40 749.0 48.70 bility of some error from this source. The extreme sluggishness of flow of the Mol. wt. (cryoscopically) 306.0 663.0 762.0 three samples a t 37.8” C. indicates that The concordance between the mothe results are of a proper order of lecular w e i g h t s obtained by the two magnitude. There is no evidence that the samples are plastic rather than methods indicates that polymerization occurs to a s l i g h t e x t e n t , if a t all. viscous. A very slight pressure will The slight discrepancy between the two c a u s e slow but definite movement in the most sluggish of the samples. sets of r e s u l t s m a y be attributed t o possible slight polymerizrttion or, more The congealing points of the samples probably, to experimental error. were determined by a method analogous t o that used for the pour point of petrol e u m p r o d u c t s (4). T h e c o o l i n g Ac KNOWLED GME NT 5 samples were held in a horizontal posiThe writer wishes to e x p r e s s his FIGURE 4. REL.4TION OF CHLORINE tion for 3 seconds after each temperaCONTENT AND SURFACE TENSION thanks to several of his students who ture drop of 2” C. The temperature collected the surface tension data, and reading when no flow was discernible was taken as the congealing point. The samples were vitre- to the Continental Oil Corporation who furnished the oils ous in all cases when the congealing point was reached. The used for viscometer calibration. results obtained are plotted in Figure 3. LITERATURE CITED The surface tensions of the samples were obtained a t 37.8” C., employing a du Kouy tensiometer. The results are (1) Brooks, “Chemistry of the lion-Benzenoid Hydrocarbons,” plotted in Figure 4. p. 102, Chemical Catalog, 1922. The molecular weight of the final product may be calcu- (2) Dakin and Dunham, Brit. Med. J.,1918, I, 51-2. (3) Davis, U. 5. Patent 1,815,022 (1931). lated from the equation: (4) Federal Specifications Board, Bur. Mines, Bull. 323B, 37,
L_
iCllT,
36.46 X 100 = % c1 403 34.45~ where 5 = atoms of c1replacing H in the paraffin molecule 403 = original mol. wt. 403 34.452 = mol. wt. of chlorinated product
+
+
ITALIAN SYNTHETIC CAMPHOR ISDCSTRY. The S.A. Marengo
of Genoa is the only producer of synthetic camphor in Italy. It is also an important producer of cop er sulfate; the controlling interest is held by the Montecatini, t i e largest Italian manufacturer of copper sulfate. The synthetic camphor plant, however,
Method 20.12 (1927). (5) Treadwall and Hall, “Analytical Chemistry,” 4th ed., Vol. VII, p. 329, Wiley, 1911. RECEIVEDMarch 27, 1933. Presented before the Division of Petroleum Chemistry at the 85th Meeting of the American Chemical Society, Washington, D. C., March 26 to 31, 1933.
is operated independently. Official trade figures show 358 tons of camphor exported in 1931; 384 tons, in 1932; and 99 tons, during the first 5 months of 1933. Principal export markets are
the United States, India, France, Germany, England, and Austria.
