July 1, 1921 



THE INDIA RUBBER WORLD 



745 



to a more active substance, or combines with the decomposition 

 or alteration products of the original substance with the forma- 

 tion of a zinc salt, which is responsible for the increase both in 

 the sulphur coefficients and tensile strength of the mixture. Our 

 results with aniline as the accelerator, however, do not indicate 

 the formation of such a salt. 



Thus, in the presence of zinc o.xide, the activity of aniline and 

 diphenylthiourea as accelerators appears to be of a different 

 nature. Evidently, an acid substance, probably a thiocarbamic 

 acid, capable of reacting with zinc o.xide, is fonned as one of the 



different intervals of time up to 240 minutes.'" The sulphur co- 

 efficients and physical properties of the different cures for each 

 mixture were determined. These results are given in detail, ^rp 

 Table II. Generally speaking, the results obtained were in good 

 agreement, and fairly smooth curves for physical properties were 

 obtained." 



CONCLUSIONS 



(1) In a rubber-sulphur mixture,, the activity of aniline in the 

 acceleration of vulcanization is much greater than that of a molec- 

 ularly equivalent quantity of diphenylthiourea. 



decomposition products of diphenylthiourea. The excess accelerat- 

 ing activity is attributed to this zinc salt. When aniline is em- 

 ployed as the accelerator, there is no evidence of such salt 

 formation. experimental part 



The present experiments were designed to effect a comparison 

 of the sulphur coefficients and physical properties of represent- 

 ative mixtures when accelerated by 0.01 -gram-molecular quantities 

 of either aniline or diphenylthiourea. The six following mixtures 

 were employed for this purpose, and each was vulcanized for a 

 series of cures : 



A — Kubber-sulphur control 



B — Rubber, sulphur, and aniline 

 B-I — Rubber, sulphur, and diphenylthiourea 



C — Rubber, sulphur, and zinc oxide control 



D — Rubber, sulphur, zinc oxide, and anihne 

 D-I — Rubber, sulphur, zinc oxide, and diplienylthiourea 



The quantities of each substance employed in these mixtures 



are shown in Table I. The amounts of aniline or diphenylthiourea 



Table I 

 Mix- Mix- Mix- Mix- Mix- Mix- 

 ture ture ture ture ture ture 

 Ingredient A B C D B-I D-I 



Rubber 100.00 100.00 100.00 100.00 100.00 100.00 



Zinc oxide 100. 00 100,00 lOO.OO 



Sulphur 8.1 8.1 8.1 8.1 8.1 8.1 



l^niiinc 0.93 .... 0.93 



Diphenylthiourea .... .... .... .... 2.28 2.28 



added to these respective mixtures represent 0.01 gram-molecule 

 of the accelerator for each 100 gms. of rubber in the mixture. Other- 

 wise, the same general method of procedure was adopted in the 

 course of this work as in that previously reported in Part I." 



The rubber used was of good quality, first latex, pale crepe, a 

 different sample of the lot used in our former experiments. The 

 various mixtures were mixed on the mill, vulcanized, and tested 

 in the same manner as before. The physical properties of the vul- 

 canized samples were determined on a Scott testing machine of the 

 vertical type, with the jaws opening at the rate of 20 inches per 

 minute. A recovery period of 48 hours was allowed before phys- 

 ical tests were made. Combined suliihur was estimated by our 

 method previously reported in detail.'" 



The various mixtures were vulcanized at 141.S degrees C. for 



(2) In mixtures which contain zinc oxide, diphenylthiourea 

 is more active than aniline. 



(3) In mixtures accelerated by aniline, either with or without 

 zinc oxide, the same maximum tensile strength is obtained, ac- 

 companied by a higher sulphur coefficient in the absence of zinc 

 oxide than when this substance is present. 



(4) Mixtures which contain zinc oxide, and which are ac- 

 celerated by either aniline or diphenylthiourea, show large in- 

 creases in tensile strength in the early stages of the vulcaniza- 

 tion. 



(5) Mixtures which contain zinc oxide and which are ac- 

 celerated by either aniline or diphenylthiourea, attain the same 

 maximum tensile strength at approximately the same sulphur 

 coefficients. 



(6) There is apparently no general relation between the 

 physical properties and sulphur coefficients of accelerated mixtures. 



".Tournal of Industrial and Engineering Chemistry, 12. 1920, 317 



"^The India Rubber Wcrld, 61, 1920, 356. 



'^ In the experiments described in Parts I and II vulcanization was ear- 

 ned on at a temperature of 148 degrees C. 



"Satisfactory physical test results for representation graphically are 

 obtainable with considerable difficulty. We have found it necessary, par- 

 ticularly when seeking resuhs for stress-strain diagrams, to employ ' three 

 men, one to operate the machine and two to take readings. 



SHIPPING SERVICE TO RHINE POINTS RESUMED 



The Red Star Line of the International Mercantile Marine Co., 

 New York, N. Y., announces resumption of its pre-war all-water 

 service to points on the River Rhine. Transhipment via fast 

 Antwerp steamers may be made for both incoming and outgoing 

 traffic. Through rates will now be named and through bills of 

 lading issued. Goods for France, Alsace-Lorraine and the dis- 

 trict of the Saar may be shipped via Strasburg without asssess- 

 ment of the French Customs surtax. Rates will also be named 

 for rail shipments via Antwerp and Thionville to and from the 

 Rhine Valley, Switzerland, France and inland points in Belgium 

 for handling classes of cargo requiring rail transportation. This 

 restores Antwerp as a shipping point for the territory in qiipstion 

 'to the same favoi'able position it held before the war. 



