THE INDIA RUBBER WORLD 



[December 1, 1915. 



What the Rubber Chemists Are Doing. 



VULCANIZATION EXPERIMKNTS ON I'AKA KUIiBKK. 



1\ the October issue of The India Rubber World there was 

 given an abstract of a lecture by B. J. Eaton on "Variation 

 in Rate of Vulcanization of Rubber." Since that date the 

 authors' report of the original investigation has been published 

 in the •'Journal of the Society of Chemical Industry" (Vol. 34, 

 pp. 9S9-999). The authors, B. J. Eaton and J. Grantham, chem- 

 ists of the agricultural department of the Federated Malay States, 

 have there recounted their investigations, with many tables and 

 curves showing the relations between time of cure and vulcaniza- 

 tion for various samples of rubber. Supplementary to the ab- 

 stract of the lecture, mentioned above, the following summary 

 of their results will be of interest. 



1. Considerable variation exists in plantation Para rubbers 

 from the same as well as from different estates. 



2. This variation relates chiefly to its rate of vulcanization, 

 and not to its general mechanical properties, especially in the 

 case of properly prepared "first latex" samples. 



3. Given the rate of cure under specific conditions, vulcanized 

 rubber having similar mechanical properties can be made from 

 all good samples of "first latex" rubbers. 



4. Differences in mechanical properties are greater between 

 high and low-grade plantation rubbers than among first quality 

 rubbers. Some rubbers never attain the maximum mechanical 

 properties reached by others, whatever the period of cure adopted. 

 These differences in the case of "first latex" rubbers are not 

 so important to the manufacturer as the differences in rate of 

 cure, and are not of the same order. 



5. The rate of cure is due to some non-caoutchouc substance 

 in the latex, possibly protein or other organic constituent, or to 

 some product derived from these substances, which acts as a 

 catalyst and accelerates the rate of cure. 



6. This substance may be already present in the latex, or it 

 may be subsequently formed there by decomposition and taken 

 up by the rubber in variable quantity, according to the mode 

 of preparation, or, alternatively, it may be formed in the coagu- 

 lum in variable quantity, depending on the amount of serum 

 remaining or the presence of preservatives which hinder or 

 prevent its formation. These theories await investigation. 



7. Smoking, removal of excessive serum in the washing pro- 

 cess, and preservatives are among the artificial factors which 

 either hinder the formation of this substance or, if it exists in 

 the prepared rubber, partially destroy it. 



8. The catal\tic substance is probably not affected greatly 

 by heat. Whether heat destroys it, or prevents its formation in 

 the latex or partly coagulated rubber, awaits investigation. 



9. The rate of cure of a rubber under specific conditions is 

 not indicated in any way by the mechanical or any other appar- 

 ent properties of the raw material. 



10. Two alternatives are suggested to secure uniformity be- 

 tween rubbers from the same or different estates: (1) The 

 issue of certificates giving correct rate of cure and mechanical 

 properties at this cure; (2) the attainment of more uniformity 

 by uniting the rubber from latex collected during a series of 

 days into one ball or block, which may be described as the method 

 of averages. 



Over three years ago (July, 1912), Messrs. Beadle and Stevens 

 clearly showed, for the first time, that the removal of the nitro- 

 genous matter from Para rubber resulted in slow-curing rubber, 

 as indicated by low percentage of sulphur in "combination" 

 with the rubber and poor physical qualities; while the excess 

 of protein matter has the reverse effect; They particularly drew 

 attention to the influence of the protein on the speed of vulcani- 

 zation. They also pointed out the importance of their discovery 



as regards the vulcanization of synthetic rubber. In subse- 

 quent papers Beadle and Stevens have shown that not only the 

 nitrogenous matter, but also the resinous matter, affects the 

 quality and speed of vulcanization of the rubber. [See reference 

 in The India Rubber World, May, 1914.] 



CONDENSATION PRODUCTS. 

 A very interesting paper on the condensation products of 

 phenol and formaldehyde, with special reference to bakelite, by 

 Goro Matsumato, appears in the "Journal of Chemical Industry," 

 Japan, Vol. 18, page 434 (1915). Mr. Matsumato classifies these 

 various products in three groups, namely, crystallizable, soluble 

 and fusible, insoluble and infusible. His results on bakelite are 

 thus summarized ; 



(1) The whole process may be divided into three stages: the 

 initial condensation, the concentration of the products, and the 

 hardening. Reactions in all stages are accelerated 1)y certain 

 reagents. 



(2) The following may be used as condensing agents : sulphuric 

 acid, hydrochloric acid, ammonium hydrate, sodium sulphite, 

 sodium carbonate and sodium hydrate. 



(3) As a hardening agent only basic substances, as sodium 

 hydrate or ammonium hydrate can be used, of which the latter 

 is better. 



(4) The combination of sodium hydrate as the condensing 

 agent and ammonium hydrate as the hardener gives the best 

 results both in yield and quality. 



(5) With the use of cresol instead of phenol a similar sub- 

 stance is obtained. 



TEST FOR BENZOL OR ALCOHOL IN HYDROCARBON MIXTURES. 

 The well-known German chemist. Dr. Fritz Frank, in a recent 

 article mentions a method for the colorimetric estimation of 

 benzol or alcohol in mixture with hydrocarbons of the paraffin 

 series. The test is credited to Karl Dietrich, who obtained from 

 dragon's blood resin a coloring material which gives a crimson 

 color in the presence of benzol or alcohol. The test is made by 

 means of "Diacorubin paper,' which is impregnated with vary- 

 ing proportions of diacorubin resin in order to afford quanti- 

 tative color reactions in a standard test volume of liquid. 



RUBBER RESINS. 

 In a voluminous article, published serially in "Gummi 

 Zeitung," Dr. F. Jacobsohn reviews the work of many authorities 

 concerning the presence of resin in rubber latex and in various 

 commercial grades of rubber. There seems to be much doubt 

 as to the function of these resins in the plant economy, and not 

 much agreement as to their effect in rubber other than that 

 they seem to act as catalyzers during vulcanization, and conse- 

 quently are not advantageously removed except in the extreme 

 case of Pontianac, where the resin content is the chief ingredient. 



RESEARCHES ON AFRICAN RUBBERS. 

 F. Heim and others in the "Bulletin of Agricultural Intelli- 

 gence," Vol. 6, 581 pages (1915), report investigation of the 

 "Gohine" liane (^Laiidolphia hcudelotii), a source of rubber in 

 French West Africa. The writers have analyzed two samples of 

 this rubber from the Upper Senegal-Niger region and give data 

 concerning strength, extension, nerve, elasticity and permanent 

 stretch of these samples and also other samples from the same 

 variety grown in different stations and prepared by various 

 methods of coagulation. Compared with fine hard Para the 

 rubber had equal strength and greater resiliency and stretch. 

 Three samples of rubber from French Equatorial Africa, known 

 as "G'vouina Noir" or ".Andang," "Kondo" or "Pembe," and 



