THE RUBBER INDUSTRY — GIBBONS 



203 



Vulcanization was regarded as an adsorption phenomenon by 



Ostwald. . 



Ostromislensky proposed a theory which was in part a combniation 

 of the foregoing. He assumed that there was only one chemical 

 reaction— i. e., the formation of the hydrocarbon saturated by the 

 addition of sulfur; and that this compound, which would be produced 

 only in small quantity in the ordinary soft-rubber formula, was 

 adsorbed by the remainder of the rubber which had been unaffected 

 by the sulfur. 



A satisfactory theory of vulcanization should account for the change 

 in physical properties as well as for the chemical change. The most 

 commonly accepted view at present appears to be that the long-cham 

 molecules, of which the rubber hydrocarbon is assumed to consist, 

 are bound together by cross links as a result of vulcanization. The 

 exact nature of these cross links has not yet been definitely established. 



The development of theories to account for the structure of rubber 

 and the phenomenon of vulcanization are of undoubted importance 

 in expanding our knowledge of rubber, although they have not 

 yet resulted in any important practical application in the manufac- 

 ture of rubber products. 



ACCELERATORS 



In the discussion of Goodyear's work, mention was made of the 

 fact that in his first experiment he used lead carbonate in addition 

 to sulfur and rubber. Goodyear and those who made the first use of 

 his invention recognized that lead carbonate and other lead com- 

 pounds materially assisted in the vulcanization process by shortening 

 the time. It was later found that certain other inorganic materials, 

 such as lime, magnesium oxide, and antimony sulfide, produced a 

 similar effect. These materials were in general use by the rubber 

 industry until the early part of this century. 



In 1906 Oenslager introduced the use of aniline and aniline deriva- 

 tives as accelerators. He found that these compounds were much 

 more effective than the inorganic accelerators. This permitted the 

 use of smaller quantities and a greater reduction in time and temper- 

 ature of cure. This work was kept secret for a number of years. 

 In 1914 the German patent of Hofmann and Gottlob (8) was issued. 

 This was apparently the first published disclosure of organic acceler- 

 ators, and discussed the use of a number of free organic bases and of 

 their carbon disulfide addition products. From this time on, there 

 has been great activity in the field of organic accelerators. 



A large number of patents have issued on this subject and many 

 excellent scientific articles have been published. Here, however, only 

 the most important developments will be mentioned. Aniline was 



