20 



THE INDIA RUBBER WORLD 



[October 1, 1919. 



American Chemical Society 



RUBBER DIVISION MEETING. 



THE FIRST MEETING of American rubber chemists, organized 

 as the Rubber Division of the American Chemical Society, 

 took place at the fifty-eighth meeting of the Society at 

 Philadelphia, September 2-6, 1919. A large and representative 

 delegation of works chemists and others vv-as in attendance and 

 much interest manifested in the papers presented. 



Charles L. Parsons, secretary of the American Chemical So- 

 ciety, in a few well-chosen remarks, congratulated the American 

 rubber chemists on their organization as a distinct division of 

 the Society and predicted great benefit to the cause of science 

 and the welfare of the rubber industry when the realization be- 

 comes general that the manufacturer who secludes his processes 

 as secrets is certain some day to awaken to the fact that he is 

 failing to support his own interest by holding back in the inter- 

 change of ideas. 



The Committee on Physical Testing, H. E. Simmons chair- 

 man, reported recommendations on tentative methods for the 

 physical testing of vulcanized rubber goods. These included 

 sampling, test pieces, physical tests, testing machine and compu- 

 tations. The tests described are for tensile strength and fric- 

 tion, and hydraulic and steam endurance tests on various types 

 of hose and for belting, packing, gaskets, etc. 



The report was accepted and referred to the Rubber Division 

 for criticism and future adoption. 



"A New Method for the Determination of Sulphur in Rub- 

 ber Mi.xtures," by G. D. Kratz, A. H. Flower, and Cole Coolidge, 

 was read by Mr. Kratz, who reviewed the methods of Esch, 

 Spence and Young, and of Tuttle and Waters, and gave in de- 

 tail the procedure of the new method, by which it is possible for 

 one person to make 50 determinations of sulphur per week of 

 44 hours, together with other work. A single determination re- 

 quires four hours' work. 



"The Extraction of Rubber Goods" was presented by S. W. 

 Epstein and B. L. Gonyo, of the Bureau of Standards. The 

 solvents considered were (1) chloroform, (2) acetone (45) and 

 carbon disiilphide (55) ; and acetone (40) and chloroform (50), 

 and a tabulation of results was shown indicating the relative 

 efficiencies of the solvents following initial extraction of the 

 vulcanized rubber sample for eight hours with acetone. The 

 advantage of the mixed solvents was marked and somewhat in 

 favor of the acetone-carbon disulphide mixture. 



"The Theory of Balloon Fabric Protection" was briefly treated 

 by the division chairman, Dr. John B. Tuttle. Balloons are 

 classified in Army service as : 



(1) Nurse balloons, capacity 5,000 cubic feet. These are used 

 for transporting supplies of gas only. 



(2) Kite balloons, capacity 160,000 cubic feet. They are used 

 as captive observation balloons, requiring low visibility as tar- 

 gets and weather-proofing to withstand at least sixty days' ex- 

 posure. 



(3) Dirigible balloons, capacity 165,(X)0 cubic feet, requiring 

 practically the same protection as kite balloons. 



Specifications of weights and constructions were given for 

 fabrics for each sort of balloon named, including dyed plies and 

 outside aluminum coating for protection against the heat and 

 actinic rays of the sun 



A paper by Mr. W. W. Evans on "Balloon Seam Construction 

 and Cements" embodied the results of experimental studies at 

 the B. F. Goodrich plant. The temperature of the inside of a 

 balloon is from 20 to 25 degrees F. higher than that of the out- 

 side air. This temperature can be lowered about five degrees by 

 an outside coating of aluminum. A stock cement was used, con- 

 sisting of specially washed Para dissolved in 50 per cent 



by weight of benzol. .\ series of working cements prepared 

 from this, using various rubber and resin ingredients, was in- 

 vestigated. A certain proportion of resin was proved advan- 

 tageous, also cold vulcanization at the time of making the seam. 

 Seams are cemented and lapped three-quarters of an inch, wiped 

 with a solution of one-half per cent solution in a mixture of 

 equal parts of carbon tetrachloride and benzol, and rolled in 

 contact. The seams are reinforced by the application of 

 cemented strips 1-J4 inches wide on the outer balloon surface and 

 two inches wide on the inside. 



Discussion of Dr. Tuttle's and Mr. Evans' papers developed 

 that on account of the shortage of rubber during the war the 

 Germans were compelled to use cellulose acetate and dyed 

 fabrics in balloon construction. In point of efficiency Ameri- 

 can practice in the balloon fabrics and rubber construction was 

 equal to that of any other nation. 



The expansion of rubber compounds during vulcanization has 

 been studied experimentally by C. W. Sanderson. A volume of 

 one cubic inch was placed in a cylindrical cavity. Temperature 

 increase of five degrees F. per 20 minutes was applied by means 

 of a surrounding steam atmosphere. The rubber was free to ex- 

 pand upward only against the force of a graduated spring and 

 this motion communicated to a recording device modified from 

 a steam engine indicator. Springs of 10, 50. and 100 pounds 

 strength were used. The ten-pound spring v/as not sufficiently 

 strong to prevent porosity in the sample. The results showed 

 that the higher the quality of the rubber compound the higher 

 was the coefficient of expansion. After the first IS minutes of 

 heating, the recorded curve of expansion became a straight hori- 

 zontal line. Fine Para shows a slower expansion than brown 

 crepe. Milling increases the rate of expansion and over-milling 

 will deteriorate fine Para in this respect to the expansion rate 

 of brown crepe. The increase of specific gravity in cured over 

 uncured rubber compositions is due to elimination of contained 

 air. The contraction of a rubber compound after cure is greater 

 than its expansion during cure. 



.\ paper on "The Volume Increase of Compounded Rubber 

 Under Strain," by H. F. Schippel, was particularly interesting 

 and illustrated by a simple and striking experiment. The theory 

 was advanced that under strain the rubber in a cured rubber 

 mixing is drawn away from each particle of mineral matter, 

 forming vacua on opposite sides of the particle. This condition 

 results in a distinct increase in volume varying with the elonga- 

 tion and is made evident experimentally by an apparent decrease 

 of specific gravity. 



The experiment used in illustration was as follows : a cured 

 high-grade compounded ring, suitably proportioned as to di- 

 ameter and weight was stretched over a short cylinder of par- 

 afiine and a light elastic band snapped over both. This com- 

 l)ination was seen to float in a tall glass vessel of water. That 

 the floating effect was due entirely to the presence of vacua 

 formed by stretching the ring over the paraftine plug was demon- 

 strated by removing the ring from its strained position and 

 holding it in place on top of the paraffin, retaining it there 

 by means of the same elastic band. When placed in water the 

 combination slowly sank to the bottom of the vessel, due to 

 the lessened volume of the unstrained ring by the elimination of 

 the vacua. 



J. H. Scott led a symposium on "The Action of Accelerators 

 During Vulcanization." His paper was a comprehensive review 

 of the work of Dr. Spence and himself on the efifect of sodium 

 hydroxide, soda-lime and piperidine. The ideal catalyst is one 

 the minimum quantity of which will give the maximum stimula- 



