560 



THE INDIA RUBBER WORLD 



Judging by the exteriors, with all the compounds a beginning 

 of vulcanization took place, but in no case did a well-cured 

 product result. Still, going by the exterior and the rate of dis- 

 solving in benzene, all mixtures were more cured than those of 

 raw rubber mixed with nitro and dinitrobenzene, without the 

 addition of litharge. It seems possible, therefore, that with these 

 compounds also, with the aid of a suitable accelerator, good 

 vulcanization could be obtained. 



VISCOSITY TESTS. 



A solution of one gram of rubber and 400 mgrs. dinitrobenzene 

 in 100 cc. benzene was kept for some days in a brown bottle, 

 after which the viscosity was measured, both in the light and in 

 the dark. The resulting tests show that the viscosity of the 

 rubber solution diminishes verj- rapidly under the influence of 

 m.-dinitrobenzene in the light, even so rapidly that it was im- 

 possible to measure the viscosity in light, although an increase 

 takes place, as is found from a measurement in the dark. 



The same tests were repeated after the rubber solution had 

 been heated for one-half hour at 65 degrees C, after adding 

 dinitrobenzene. The concentration of the solution before and 

 after heating was the same. 



The results obtained show that the viscosity is increased under 

 the influence of dinitrobenzene \vhi\t heating is applied, and again 

 declines rapidly in the light. From this one would be led to 

 assume that dinitrobenzene assists both depolymerization of 

 rubber solutions by light as well as the polymerization by heat. 

 The vulcanization with dinitrobenzene could be regarded, there- 

 fore, as a polymerization by heating. Analogous with this the 

 vulcanization with sulphur could be regarded as an acceleration 

 of the polymerization, as assumed by Bernstein^ and Kirchor,* 

 while in addition, a combining of sulphur would have to be as- 

 sumed to take place as a secondary process, either chemically 

 or physically^ 



VULCANIZATION OF RUBBER BY ULTRA-VIOLET RAYS. 



The following excerpt on the vulcanization of rubber by ultra- 

 violet rays is from a series of articles on ultra-violet rays and 

 their industrial applications by Ellis and Wells in "The Chemical 

 Engineer," July, 1918, page 298: 



Practical vulcanization of rubber by ultra-violet rays may be 

 carried out with Olivier's apparatus (United States Patent No. 

 1,256,496, February 12, 1918). Olivier notes that rubber vul- 

 canized by means of ultra-violet light is particularly useful for 

 cementing purposes, since the treatment produces thick elastic 

 liquids which are real liquid rubbers. With power cementing 

 processes, the surfaces of rubber to be cemented were coated 

 with a solution containing 6 to 12 per cent of rubber and usually 

 several layers of such cement were necessary to effect cementing. 

 With this method of producing the solution a much more dilute 

 solution can be obtained than heretofore. In fact, the dilution 

 may be 0.5 to 0.6 per cent. 



When this latter solution is used for cementing, the two 

 rubber surfaces absorb the solution, and it is claimed that upon 

 placing the surfaces in contact a real autogenous union of the 

 two rubber surfaces can be obtained. When surfaces of rubber 

 are so united, they are not separated by a comparatively thick 

 layer of cement, as with former cements, but they are in imme- 

 diate contact on account of the penetration due to the dilution 

 of the solution. 



In carrying out the process, the first factor to be fixed is the 

 duration of the exposure to the ultra-violet rays. Experience 

 has shown that after a certain time of exposure, the decom- 

 position of the rubber increases rapidly, whereas the vulcaniza- 

 tion effect increases to only a small extent. The duration of 

 exposure of course changes according to conditions, depending 

 on the size of lamp used, the thickness of the solution, and the 

 distance of the solution from the lamp. When using a 220- 

 volt, three-ampere quartz lamp, and a solution a fraction 

 of a millimeter in thickness placed at a distance of five centi- 

 meters from the lamp, the duration limit would be 40 seconds. 



'"The Rubber Industry," 164, London, 1914. 



• "Kollcid-Zeitschrift," !4. 3.=:. 1914. 



^ Van. Iterson. "Communications of the Netherland Government Institute 

 for Advising the Rubber Trade and the Rubber Industry," Part VIII, page 

 239; The Ineia Rubber World. April 1, 1919, page 362. 



When solutions of rubber are being vulcanized with ultra- 

 violet rays, the .sulphur usually used can be replaced by sulphides 

 and, in a general way, by any sulphides which can be decom- 

 posed by ultra-violet rays, such as carbon disulphide, allyl 

 sulphide, or antimony sulphide. After vulcanization, when these 

 sulphides are used, there is no uncombined sulphur left in the 

 solution as, accordinj? to Olivier, it is precisely the sulphur which 

 is decomposed out of the sulphides which allies itself with 

 the rubber. Vulcanization can also be effected by adding to 

 the solution at the same time ordinary free sulphur and carbon 

 disulphide. 



Under thc.se condiiions, vulcanization occurs concurrently be- 

 tween the rubber and the sulphur decomposed out of the sul- 

 phide. 



DIFFUSION OF GASES THROUGH INDIA RUBBER 



A study of the diffusion of gases through india ruliber by Sir 

 James Dewar appears as an appendix to a lecture on "Proljlems 

 of Hydrogen and the Rare Gases" in the "Proceedings of the 

 Royal Institute," volume 21, page 543. A few of the interesting 

 results are as follows : 



The relative rates of diffusion of the following gases, through 

 Para rubber membranes 0.1-mm. thick, at one atmosphere pres- 

 sure, and 15 degrees C. are: air, 10; nitrogen, 0.69; carbon 

 monoxide, 0.94; helium, 1.75; argon, 1.28; oxygen, 2.0; hydrogen, 

 5.6 ; carbon dioxide, 14.0. The absolute rate for air is 2.00 cc. 

 per square centimeter per day. The relative rate varies with the 

 temperature. It is difficult to associate the order of diffusibility 

 with any chemical or physical properly. For example, the rate 

 of diffusion of helium, the most volatile of gases, is one-eighth 

 that of carbon dioxide. 



The rate of diffusion through india rubber of gases dissolved in 

 various liquids was investigated. The relative rate of gases in 

 solution is not so low as their proportional lowering of the vol- 

 ume concentration in the liquid. Water, for example, at IS de- 

 grees C, dissolves 1/60 of its volume of air or hydrogen, but the 

 rate of diffusion from air or hydrogen-saturated water is only 

 reduced to one-quarter of that of the rate in air. The behavior 

 in alcohol is the opposite. .Mr goes through the membrane with 

 equal rapidity whether alcohol is around it or not. 



"The Mutual CoNDENS.^TI0N or Unsaturated Compounds in 

 Connection with Terpenes, Resins and Rubber." H. J. Prins. 

 Hilversum. "Chemisch Weekblad," Volume 16, 64-74 (1919). A 

 review, with particular reference to polymerization of unsaturated 

 compounds and the vulcanization of rubber. It is maintained that 

 this type of reactions cannot be explained under one grouping 

 without the aid of the valence theory and the theory of mutual 

 activation. ("Chemical .'\bstracts," May 20, 1919, page 1071.) 



CHEMICAL PATENTS. 



THE UNITED STATES. 



Drocess of Producing Rubber Compositions and Vulcani- 

 ■'■ ZATION Product, consisting of adding to rubber a wet precip- 

 itate of barium sulphate formed in the presence of a colloidal gel 

 (animal glue), mixing the resultant precipitate with the rubber, 

 drying the mix. and heating it with a vulcanizing agent to effect 

 vulcanization. 



The homogenous vulcanized product formed by adding to 

 rubber and animal glue formed into a gel by water, mixing 

 the gel with the rubber, driving off the water, and heating the 

 resultant dry mix with a vulcanizing agent to effect vulcani- 

 zation. (Robert C. Hartong, assignor to The Goodyear Tire & 

 Rubber Co., both of -A-kron, Ohio. United States patent No. 

 1,301,693.) 



Impregnation of Fabrics for Balloons. The fabric is first im- 

 pregnated with soft paraffine or petroleum, etc.. and coated on 

 one side with a compound of rubber, ceresin wax, litharge, and 

 sulphur, applied in a dissolved state and subsequently vulcan- 



