AlGL-ST 1. 1920.] 



THE INDIA RUBBER WORLD 



715 



Methods for Physical Testing of Vulcanized Rubber Goods. 



(I) 



SAMPLNG. 



Samples shall be taken directly from the finished ma- 

 terial. These should be sealed, and marked with 

 maker's name, date of sampling, kind of material and 

 sufficient other data to insure easy and complete identification. 

 The sample should be of such size as to permit of part being 

 taken for test and the remainder stored for future reference, 



should the oc- 



casion arise. 

 Ever y precau- 

 tion must bo 

 taken to prevent 

 contamina- 

 tion of the 

 sample by any 

 foreign ma- 

 terial, and it 

 must always be 

 stored in a cool 

 place. The ob- 

 ject of these 

 precautions is 

 to insure that 

 the sample shall 

 be received in 

 exactly the 

 same condition 

 as it was when 

 taken from the 

 original lot. 



(2) In gen- 

 eral, the follow- 

 ing shall repre- 

 sent the amount 

 of sample re- 

 quired for test: 



(a) Tires, 

 tubes, etc., of all 

 kinds. One to 

 be selected at 

 random from each lot of 500 or less. 



(b) Hose. Three lengths from each lot of 5,000 feet or less. 

 A 3-foot section to be cut from each length selected, for bursting 

 tests : other tests to be made on the remainder of the same 

 sample., 



(c) Belting. One sample 12 inches long from each roll of 

 belting under 6 inches in width and 6 inches long from belting 

 over 6 inches in width. 



(d) Packing. One sample 10 inches long cut across the full 

 width of the sheet from even' lot of 2S0 pounds or less. 



(e) Molded and lathe cut goods. One piece selected at ran- 

 dom from every 200 pieces or less. 



PREPARATION OF TEST PIECES. 



(I) For tensile, elongation and set. strips shall be cut 175 

 mm. long by 25 mm. wide by approximately 2 mm. thick. In 

 every possible case these strips should be cut from the sample. 

 In cases where the sample consists of a large block, as for in- 

 stance, a section of a solid tire, the strips may be obtained by 

 using heavy meat-slicing machine. When the material is made 

 up with layers of fabric, as in the case of rubber hose, the first 

 step in preparing specimens for the tension test is to separate 



1. Staxd.\rd Dies for Cutting and Gaging Test Pieces. Fig. l-.A. 

 Cutting Samples of Vulcanized Reclaimed Rubber. 



•Report of Committee of the Rubber Division on Physical Testing. 

 Published by courtesy of the American Chemical Society. Paper read 

 before the Rubber nivision of the American Chemical Society, at St. 

 Loais, Missooiri, April 14-15, 1920. 



the rubber from the fabric. Unless the frictioning is very poor, 

 this will necessitate the use of a solvent. If there is more than 

 one layer of fabric the easiest way is to remove the first layer 

 along with the rubber. The rubber is then separated from the 

 adjoining layer of fabric, using C. P. benzol blown from a wash- 

 bottle. Narrow strips are more easily handled than larger pieces, 

 and there is less danger of injuring the rubber. Great pains 



should be taken 

 during this 

 operation b e- 

 cause any flaw 

 or local imper- 

 fection will 

 seriously vitiate 

 the results. The 

 rubber should 

 be allowed to 

 rest for four 

 liours. in order 

 that it may re- 

 cover from the 

 stretching it has 

 received and 

 that the benzol 

 may thoroughly 

 evaporate. 



(2) Wherever 

 possible test 

 strips should be 

 cut in the trans- 

 verse direction. 

 In case tests are 

 desired in the 

 longitudinal di- 

 rection, they 

 should also in- 

 clude the trans- 

 verse. D i r e c- 

 tions should be 

 recorded with 

 the results of the tests. 



(3) In case the articles to be tested will not permit of pieces 

 as above taken, then small sample pieces shall accompany each 

 lot. These may be cured in the form of sheets approximately 2 

 mm. thick and of such shape as to give the desired length and 

 number of strips, provided further that they shall be guaranteed 

 by the manufacturer to represent truly the average composition 

 and cure of the article delivered. From the piece described 

 above, test pieces shall be cut using for this purpose the standard 

 dies shown in Fig. 1, except with samples of vulcanized reclaimed 

 rubber for which the die Fig. 1-A shall be used. The cutting 

 edge of the die shall be kept sharp and the test pieces may be 

 cut best by striking the die a quick heav>' stroke with a mallet, 

 in which case the die should -be pro\Tded with a handle, or it 

 may be done by attaching the die to the rack of an arbor press, 

 Fig. 2. The piece should be cut against a backing of fine card- 

 board, hard rubber or leather. The backing or cloth impression 

 shall be removed from the test piece by buffing. Where test 

 pieces are cut from strips of uneven thickness, they shall be 

 buffed to a uniform thickness for about 8 cm. over the middle 

 portion of the strips, after which the test pieces are cut with 

 the die. 



(4) For stocks having high elongation such as pure gum, a 

 shorter die giving only 25 mm. constricted portion should be 

 used. 



