888 



THE INDIA RUBBER WORLD 



September 1, 1921 



examined was rolled into a thin sheet and dried tu constant 

 weight in vacuum over calcium chloride or in a drying oven at 

 100 degrees C. l''our-tenths to eight-tenths-grani of the dried sam- 

 ple was then scaled in a thick-walled tube from which the air had 

 been displaced by oxygen and heated for 5 to 20 hours at 100 

 degrees C. The tube was then allowed to cool, the rubber re- 

 moved, weighed rapidly, and the increase in weight taken as an 

 inverse measure of the durability of the sample. The increase 

 in weight shown by a sample of good rubber in five hours 

 amounted to from 2 to 4 per cent. 



Ditmar also conducted tests for determining the influence of 

 various constituents, such as powdered glass' and l>arytc.s°, on 

 the oxidation of rubber as well as tVe influence of vulcanization 

 pressure". 



In connection with work on aging and oxidation one should 

 not neglect citing the work of Harris" on detennining the struc- 

 ture of rubber by means of ozone, since these researches 

 are of importance in throwing light on the nature and consti- 

 tution of the rubber molecule. 



In a similar sense the discovery by Spence'' of the presence 

 of oxidases in rubber, as well as his work on after vulcaniza- 

 tion, should be recognized for its effect on research along these 

 lines. 



The majority of the work on aging from 1906 to date was 

 conducted for the following purposes : to study the theoretical 



of the rubber molecule. At temperatures in the neighborhood 

 of 80 degrees C. pure rubber was readily attacked by oxygen, 

 and it was not difficult to bring about complete oxidation of a 

 film. 



Later Peachey and Leon" amplified these earlier researches 

 by conducting a series of experiments on the effect of moist 

 oxygen on vulcanized as well as crude rubber. One of the 

 results noted was that vulcanized rubber oxidized far less rapid- 

 ly than crude rubber, but that the amount of oxygen consumed 

 was ultimately the same. The oxidation products were analyzed. 



Bing'' had earlier determined the presence of sulphuric acid 

 in vulcanized rubber, and the accelerating, deteriorating effect 

 of copper salts. No change in normal oxidation was observed 

 in nine months, but when copper chloride was used deteriora- 

 tion set in within a week. 



A quantitative study was made by Kirchhof" on the oxida- 

 tion products, both of crude and vulcanized rubber. 



Gorter" and Kerbosch", as well as Peachey and Kirchhof, 

 already mentioned, have studied the theoretical nature of the 

 oxidation of rubber. Van Rossem's work'' in which conclu- 

 sion that the oxidation of rubber is a secondary process which 

 can take place only when rubber has been previously depoly- 

 merized to a definite critical viscosity is not in disagreement 

 with the experiments of the above mentioned. Fickendy^. 

 by exposing rubber to sunlight in tubes containing air and 



Fig. 1. At'i>.\R.\Tus iuk Testing .Vce oi- Vli.ca.vizeu Klhhkk 



nature of oxidation, to define and determine the oxidation prod- 

 ucts ; and to study the effect of aging on vulcanized rubber in 

 determining the state of cure and the "optimum" or correct cure. 

 Peachey in 1912" carried out experiments on crude rubber to 

 determine the number of oxygen atoms which are concerned in 

 eflecting complete "atmospheric oxirlation" of the r,„H,„ unit 



•Ibid, Vol. 21, 418-9, 1906 



•Ibid, Vol. 21, 234-5, 1906. 



» Chemische-Zcituni!, Vol. 31, 638-9, 1907. 



"Betichtf der Deutsche Chcmische Gescllschaft. Vol. 37, 2708, 1904; 

 V.l. 38, 1195, 3987, 1905. 



I- niochemical Journal, Vol. 3, 165, 351. Kolloid-Zeitsdirift, Vol. 10, 

 299. 1912. 



"Journal of the Society of Chemical Industry, \ol. 31. 1103-5, 1912. 



other gases, proved that the presence of o.xygen was necessary 

 to produce tackiness. 



The researches of Stevens"', de Vries^, Eaton and Day"' and 

 Schidrowitz and Goldsborough" were carried out for the purpose 

 of determining a correct or "optimum" cure. Aging is studied 

 with this purpose in mind and also for its effect on the stress- 



" Ibid. Vol. 37, 55T-60T, 191S. 

 i« Kolloid-Zcitschrift. Vol. 4, 232-5, 1909. 

 i« Kolloid-Zcitschrift, \'ol. 13, <t9-61, 1913. 

 ^^ Mededcclingen over Rubber, No. 11. 

 "Ibid, No. 111. 



" The Rubber Industry, 1914. p. 149. Communications rf the N»ther- 

 land (jovernment Institute, Part 4. p. 120. 

 -■» K< lloid-Zeitschrift, \M. 9. 81, 1911. 



