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THE INDIA RUBBER WORLD 



[January 1, 1912. 



Uniform Tests for Rubber Products. 



IN a circular addressed to the German rubber industry, the 

 Gross-Lichterfelde Material Testing Bureau has elaborated 

 a plan for the application to rubber products of tests, similar 

 in principle to those which have been adopted for paper, lubri- 

 cants and cement. This plan, it is remarked, depends for its 

 success upon the co-operation of rubber manufacturers and 

 consumers, following the general ideas outlined in the India 

 Rubber World in the issues of October 1, 1911 (page 23) and 

 December 1, 1911 (page 107). 



With this view it is proposed to carry out, from old and 

 new standpoints, a series of tests upon various standard com- 

 pounds of soft rubber. The principal object will be to investi- 

 gate the processes already in use and if necessary to supple- 

 ment them with due regard to practical conditions. For this 

 purpose it will be necessary for the Bureau, in the first place, 

 to test as many compounds as possible ; then discussing the 

 results with representatives of the various factories, in order 

 (as was the case with paper) to arrive at generally recognized 

 and uniform methods of testing. 



As the preparation of the samples for testing could not be 

 fully carried out in tlie laboratory of the Bureau, and would 

 take too long, it is considered preferable for these samples to 

 be prepared in the regular course of factory operation. The 

 Bureau therefore requests the support of the German rubber 

 industry in the form of the necessary samples. As far as can 

 be foreseen, the results of the contemplated trials will be of 

 considerable advantage to the rubber industry, while also pro- 

 moting in a general way the development of mechanical test- 

 ing, in perfecting which the most diverse technical circles are 

 interested. Special attention is directed to the confidential 

 nature of these tests and to the official secrecy which will at- 

 tend their detailed operation. In the subsequent publication of 

 results care will be taken to prevent the interests of the various 

 rubber factories from suffering, the names of the manufac- 

 turers not appearing in connection with the samples tested. 



METHODS OF TESTING. 

 The plan of testing includes tests for rupture, pressure, wear, 

 durability, hardness and elasticity. 



Under the head of rupture, tests will be made as soon as 

 possible of ten ring samples, with measurements of extension. 

 the appearances of hysteresis being recorded as to some of the 

 samples. Ten further tests will be made with ring samples 

 which have been subjected to preliminary tests in the Martens 

 extension machine, .\nother series of rupture tests will deal 

 ■with the condition (1) (five tests) after the samples have been 

 kept a year, without special protection from light, and (2) 

 (fifteen tests) after being subjected to an accelerated process 

 of ageing, during one to eight days, at a dry heat of 150 deg. F. 

 Tests of pressure, twelve in number, will be made with rub- 

 ber cylinders in a press on the Martens system, change of 

 form and elasticity in conjunction with pressure being thus 

 defined. 



Tests for wear, three each, will be made with balls of 1 1-5 

 inches diameter by an apparatus on the Martens system, and 

 with rings by an apparatus on the Mai system. A third test 

 of the waste discs resulting from the stamping out of the 

 rings is being at present studied. 



Tests for durability will be made in two forms, with four 

 rings on the Martens-Schopper durability testing machine, and 

 with ring samples stretched upon glass plates, conditions being 

 observed in a room and in the open air, as well as under dry 

 and moist heat. 



Tests for hardness will be made with the Brinell-Martens 



ball tester, while tests for elasticity would lie probably made 

 with a new apparatus still to be tried. 



SAMPLES FOR TESTING. 

 For the carrying out of the proposed tests there would be 

 required of each description of rubber to be tested : 



a. 1 sheet of rubber, J4 inch thick, 24 inches long, 24 inches 

 wide ; 



b. 12 rubber cylinders of 2-5 inch diameter and 2-5 incli 

 height ; 



c. 5 rubber balls of 1 1-5 inches diameter. 



The samples a to c are to be molded out of the same com- 

 pound in one operation and to be vulcanized under similar con- 

 ditions. The vulcanization should be efi^ected as far as possible 

 in the same apparatus, but in any case at the same temperature 

 and with equal duration. The separate plates should be as far 

 as possible uniform in thickness, with a smooth surface, free 

 from blisters, while the cylinders must have smooth surfaces 

 and clean edges. The balls must be special, with a .smooth 

 and regular surface. 



When samples are sent in, the date of vulcanization is to be 

 given. They should be sent, as far as possible, immediately 

 after manufacture, so that they may be tested under approxi- 

 mately uniform conditions. The samples should only be pre- 

 pared as soon as a request for same is made by the Bureau, 

 to prevent the accumulation of samples waiting to be tested. 

 The sheets ought not to be rolled but packed in cardboard 



QUESTIONS TO MANUFACTURERS. 



To facilitate the work of the Bureau and to enable it to call 

 for the necessary samples, a sheet of questions accompanies this 

 circular, in connection with which the respective manufacturers 

 are requested to indicate the classes of rubber goods they make, 

 and of which they can furnish samples in accordance with the 

 above specifications, indicating in every case" the origin of the 

 crude rubber used. 



Subjoined is the classification of the various branches of the 

 industry, in accordance with which the replies of the various 

 manufacturers are to be given : 



1. Hose for technical and laboratory purposes (ex- 

 cepting pneumatic hose). 



2. Parts of valves. 



3. Buffers. 



4. Parts of packings. 



5. Tires. a. Solid. b. Pneumatic. c. Covers. 



6. Insulating materials (cable coverings, etc.). 



7. Rubber driving belts. 



8. Rubber transport belts. 



9. Rubber rolls. 



10. Roller cloths. 



11. Rubber thread. 



12. Rubbered fabrics. 



13. Floor tiling. 



14. Rubber stoppers. 



15. Rubber compounds for surgical articles. 



16. Rubber compounds for other purposes not specified. 



REGULAR QUALITIES TO BE SAMPLED. 

 Particular stress is laid upon the fact that in the interest of 

 the most advantageous utilization of the results of the tests, con- 

 siderable importance attaches to the samples not being from 

 specially prepared compounds, but that they should represent 

 the compounds regularly used in the manufacture of the articles 

 indicated by the respective manufacturers as constituting their 

 products. Only in this way can the comprehensive work of the 

 bureau produce the anticipated results. 



