July 1, 1919.] 



THE INDIA RUBBER WORLD 



What the Rubber Chemists Are Doing. 



VULCANIZATION WITHOUT SULPHUR. These figures tend to show that after 10 to 15 minutes the 



THE RESULTS obtained by L. Ostromyslenski in vulcaniz- sheet exhibits its best mechanical properties, which decline on 



ing rubber without sulphur, that were published in The PJo'o"ged curing. Initially the rubber, on increasing the time 



T -D n; ^T u , ir,,^ ^r J -VT °^ ^urc, becomes somewhat stiffer. After some time this ceases 



India Rubber World, November 1, 1916, page 65, and No- and the curves of the stress-strain diagram begin to run parallel, 



vember 1, 1917, page 84, have been reviewed by W. Bunschoten,' If the vulcanization be continued the only consequence is that the 



who has made an extended series of experimental investiga- ^"'^ point is situated lower on the curve; in other words, the 



tions on the subject, the results of which are quoted below: breaking load is diminished While the sample with the highest vul- 



^ ' " " canization coefficient cured the faster in these experiments, this 



ACTION OF ACCELERATOES WITHOUT SULPHUR. "^^V "Ot be accepted as a rule. 



T, If- . . . 1 1 .u 1 . J • Other mixtures were prepared, consisting of 100 parts sheet 



It seemed of importance to test whether accelerators used in rubber (vulcanization coefficient 4.5), 8 parts litharge and re- 



the normal sulphur-curing process would show catalytic action spectively, 1, 2, 3, 4, 6 and 8 parts of m.-dinitrobenzene ; also of 



ma mixture without sulphur and thus lead to a well-vulcan- iqq parts sheet rubber (vulcanization coefficient 4.5), 4 parts 



ized product. In order to carry this out, mixtures were made m.-dinitrobenzene, and, respectively, 2, 5, 8 and 11 parts of 



of he following composi ion : 100 parts raw rubber 4 parts y,^^ ^^e vulcanization was carr ed out for increasing 



dinitrobenzine, 1 part accolerene or instead o the latter 1 par p^Hods in the oil bath at 147 degrees C. The results are seen"n 



vulcaate. and these cured for /^ 1, V/2, 2 2^ and 3 hours at Table III, from which it is evident that with increasing quantities 



147 degrees C an the oil bath. The result was that the prod- „£ n,.-dinitrobenzene and litharge the velocity of vulcanization is 



ucts were not Vulcanized and m these experiments these ac- increased j- u a u is 



celerators were without effect. 



Ostromyslenski found that different metallic oxides which Table III. Influence or Increasing Quantities of M.-Dinitrobenzene 



accelerate the normal vulcanization process, in contradistinction and Litharge on the Mechanical Properties and the 



to the above-named organic accelerators, do promote the curing Veiocitv of Vulcanization. 



without sulphur. Stevens^ confirms that vjith mixtures of nitre 10 Minutes' Cure. 20 Minutes' Cure. 60 Minutes' Cure, 



compounds to which litharge has been added vulcanization does , * — ^ , -» , , * — ,, 



take place. All of the following tests were made with the addi- Composi- M.-Di- Breaking Elonga- Breaking Elonga- Breaking Elonga- 



tion of litharge, and it was found that vulcanization resulted "™ f/^- K^t^t at BrTak. K^ms. at 'Cak. Kgms. at 'fireak. 



In order to judge as to the behavior of various rubbers with Mixture, zene. Per Cm^ Per Cent. PerCm^. Per Cent. Per Cm». Per Cent. 

 reference to this new curing method, two different raw rubbers 



were used, namely, a slowly vulcanizing crepe and a fast vul- Rubber f 2 70 5 938 108 870 7" 772 



canizing sheet. The vulcanization coefficients (quantity of com- lOO J 3 lOo' 1,005 106 818 79 715 



bined sulphur calculated on 100 parts of raw rubber) of these Litharge i 4 103 '798 ... ... 51 640 



rubbers were, respectively, 2.6 and 4.5 in a mixture of 7^ per ^ 1 | -j^ ^^j j^^ ^°^ ^| ^^ 



cent of sulphur and 92^< per cent of rubber after vulcanization 



for V/i hours at 50 pounds gage pressure. Litharge. 



With these rubbers the following mixtures were made : 100 raw ''^"oo" 



rubber, 8 litharge, and 4 nitrobenzine. These mixtures were vul- M.-Di- 



canized for increasing periods in the oil bath at 147 degrees C, nitro- ") 8 103 798 



corresponding to 50 pounds gage pressure. Tensile tests were ^'"^e 

 then made on a Schopper machine with the following results : 



Taete I Curing Tests Without Sulphur The influence of the curing temperature is shown by the figures 



Smoked First Latex e'^'e" '" Table IV. 



^ Sheet Vul c.Coeff. 4.5.^ _ Crepe Vulc. Coeff. 2.6. ^ ^^^^^ jy^ Influence of Cure on the Mechanical Properties. Compo- 



Time Breaking Elongation Breaking Elongation sition of the Mixture: 100 R.iw Rubber (Vulcanization Co- 



of Cure, Load, at Break, Load, at Break, efficient 4 5) 8 Litharge and 3 M -Dinitrobenzene. 



Minutes. Kgnis. Per Cm=. Per Cent. Kgins. Per Cm=. Per Cent. efi icient ^.5). b lith.^ge, and 



30 05 697 Undercured .. Tern- 5 Minutes' Cure. lOMinutes' Cure. 20 Minutes' Cure. 60Minutes' Cure. 



45 '..'.'...'!!..!! 14.5 982 Undercured . .'. Pera- , ^—^ ^ r- --' > <- —-^ ^S 7—^ > 



60 20.4 906 Undercured ... ture BreaK.ng Breaking Breaking Breaking 



90 .. 35 8 825 10.4 610 of Load. Elonga- Load. Elonga- Load. Elonga- Load. Elonga- 



120 27.8 874 22.0 704 Cure. Kgms. tion Kgras. tion Kgms. tion Kgms. ticn 



De- Per at Break. Per at Break. Per at Break. Per at Break. 



These figures show that curing took place, but that the me- Brees C. Cm^ Per Cent. Cm=. Per Cent. Cm». Per Cent. Cm^. Per Cent 



chanical properties are much inferior to those obtained with the 137 7.4 650 68 908 99 845 85 727 



normal vulcanization methods. Judging also by the exterior and J« ^f^ g^ ^H 570 ^94 793 60 682 



the course of the elongation curves leads to the conclusion that 152 40' 9^6 88 823 .". . ... 



all the test pieces were much under-vulcanized. That curing did 157 86 940 94 808 84 760 40 710 



take place was evident from the fact that the product was _, , • , .• r .1 a 1 * j „» o «„ 



insoluble in benzene although considerable swelling took place. The njechanical properties of the cured product do not seem 



Similar curing tests were carried out with m.-dinitrobenzene to be influenced much by the temperatures of curing, 



in the same proportions and at the same temperature of cure. The author expresses the opinion that while this method of 



The products obtained did not show any swelling in benzene, curing without sulphur could replace vulcanization with sulphur, 



thus proving that complete curing had taken place. (Table II.) it would not prove practicable, owing to the rapid deterioration 

 ' ■* ^ ^ i' \ 'of the product by aging. The alteration of properties that takes 



Table II. Curing Tests Without Sulphuh. place is unexplained. Probably it is not due to oxidation because 



Smoked First the acetone extract from a sample after six months' aging was 



Sheet, Vulc. Coeff. 4.5 . Latex Crepe, V ulc. Coeff. 2.6. found about equal to that of the raw rubber. From this it is 



'Breaking Elonga- Loa"dl?r Breaking Elonga- Load for' also evident that very little dinitrobenzene remains after vulcan- 



Tinie I nad, tion Elongation Load, tion Elongation ization. Also the product remained entirely insoluble in benzene, 

 ot Cure, Kgms. at Break, of 600% Kgms. at Break, of 600% 



Minutes. Per Cm.^ Per Cent. Per Cm.^ Per Cm.^ Per Cent. Per Cm.' OXIDIZING AGENTS. 



10 103 798 32 Underc'd Underc'd Undercured , , . . ... 



15 105 737 45 82.5 742 38 The curing action of several inorganic oxidation agents was 



25 87 663 54 79.5 675 57 investigated because Ostromyslenski regards vulcanization as a 



45 .■■;.■;:.■.■ 62.5 662 « 73.5 14 li kind of oxidation. The following list of substances were em- 



60 '.'...'.'.'.'. 51 640 50 73.5 629 59 ployed: arsenic acid, postassium persulphate, chloride of lime, 



75 52.5 616 48 74 622 57 potassium bichromate, potassium permanganate, potassium chlor- 



joo ,34 352 ;; 58 612 '.'. ide, potassium nitrate, sodium nitrate, manganese peroxide, and 



- .. .. potassium ferricyanidc. The test mixtures consisted of 1(K) 



1 "Communicatiou of the Netherland Government Institute for Advising grams raw rubber and 4 grams of these oxidation agents. They 



the Rubber Trade and the Rubber Industry," at Delft. Holland. were ViPat^H in fht. nil hath fnr nnp half hniir tn nnp hour ut 



'••Tournal of the Society ot Chemical Industry." February 15, 1917; also were heated in tne oil DatH tor one nait nour to one nour at 



The India Rubber World, May 1, 1917, page 451. 147 degrees C. 



