326 



THE INDIA RUBBER WORLD 



[March 1, 1913. 



Analysis and Tests of Rubberized Fabrics. 



DEALING wiili this point in a paper read at the recent 

 Congress ot Applied Chemistry, M. B. Setlik and M. J. 

 Zopka, of Prague, indicate the steps to he taken (partic- 

 ularly in the case of fabrics for liospital or domestic use, or for 

 clothing purposes) to determine their chemical and physical 

 properties, by the application of simple and expeditious tests. 

 The object of such determination is to ascertain whether the 

 fabrics are suited for the purposes intended. 



In analyzing rubberized fabrics, the general object is to 

 define the composition and quantity of the mass used for the 

 purpose of impregnation, so as to determine the quality and 

 quantity of the coating and to deline whether it contains 

 rubber, rubber substitute or some other imitation. Another 

 object of such analysis is to be able to imitate a given sample. 



Within three years the authors of the paper have examined 

 500 samples of diflferent qualities from different factories, and 

 have arrived at the conclusion that this class of fabrics can 

 be classified according to qualities, combinations and physical 

 or chemical properties, into several groups of similar quality 

 and value. The fabrics to be tested are subjected to physical, 

 practical and technical tests, and then to chemical tests. 

 Finally, to define the tensile or breaking strength, they are 

 subjected to mechanical tests. 



EX.\MIX.\TION OF A RUBBERIZED FABRIC. 



The fabric is first tested in an empirical way, its strength 

 and resistance being found by scratching it with the finger- 

 nail, by creasing it and by crumpling it between the hands. 

 It is then spread out smooth and the condition of the broken 

 places is noticed, also whether the rubberized layer is 

 detached or is in holes. Then a large piece of the fabric is 

 fixed upon a filtering frame, so that it forms a bag which is 

 filled with water. The same course is pursued with the piece 

 crumpled between the hands, both pieces being left two or 

 three days to find their respective waterproof qualities. A 

 good quality of fabric ought to absolutely resist water. 



Another comparative test is effected by submitting one 

 piece of the fabric to the action of a 5 per cent, acetic acid 

 solution, and another piece to that of a 5 per cent, ammonia 

 solution; observing at the end of two days what changes have 

 taken place. These tests are meant to represent the action 

 of urine, blood and perspiration. A square decimeter (15.50 

 square inches) is cut off the rubberized fabric and is weighed 

 by a tangential scale by which means the vi'eight per meter 

 is ascertained. The thickness of the fabric is taken by the 

 average of three different points. 



After heating a piece of the fabric for tliree hours with 

 about 100 cubic centimeters (6.10 cubic inches) of chloroform 

 it is rinsed with chloroform and then with pure alcohol. The 

 fabric is then stretched on polished glass and the coating is 

 scratched with the back of a knife or a spatula. The appear- 

 ance of the fabric treated with chloroform allows of determin- 

 ing the character of the rubber coating and to what depth 

 it has penetrated the fabric, as well as its adhesion and com- 

 bination. If the coating forms a solid and compact layer 

 which comes off easily and in large pieces it contains at least 

 50 per cent, of rubber. If there is little rubber, but if the 

 fabric is well impregnated, it can still render good service. 



There are consequently four alternative stages for the 

 coating: 



1. To swell up and easily come entirely off. 



2. To swell up. but only come off in small pieces. 



3. Not to swell up, but come off in small pieces. 



4. Neither to swell up nor come off. 



The composition of the coating is then analyzed in tlie 



usual manner, as explained by Dr. C. O. Weber in the 

 "Chemistry of India Rubber," page 256. In the removal of 

 the coating from the fabric the following process is used: 



(a) By the use of acetone, the resins, the resinous and 

 mineral oils, the wax and similar combinations are extracted. 



(b) The residue is treated by an alcoholic solution of 

 potash which saponifies the saponifiable oils, by which means 

 the rubber substitute is extracted. 



Tlie balance is rubber, mineral substance, colors, etc., which 

 can be quantitatively and qualitatively determined by the 

 ashes of the fabric. 



SWELLING UP OF A RUBBERIZED FABRIC. 



The swelling up of a rubberized fabric is more or less 

 rapid, according to whether it is subjected to the action of 

 chloroform, carbon, or sulphide of carbon. The fabric con- 

 taining resin swells up the quickest under the action of 

 sulphide of carbon. The more mineral substance or rubber 

 substitute there is in a rubberized fabric, the slower and of 

 less extent is the swelling. The layer of coating is not of the 

 same thickness on both sides of the fabric and is not uniform 

 in composition or adhesion. .-Xfter the coating has been 

 removed the fabric is heated for a moment in alcohol and 

 then washed in alcohol. It is then boiled with water and 

 weighed and is then tested for breaking strength and 

 elasticity with a dynamometer. 



As to ashes, it is evident that the less they are in quantity 

 the better the product, while their quality is likewise a matter 

 of importance. 



Certain substances, iike zinc oxide, magnesium oxide and 

 calcium carbonate, in a certain proportion, are not only not in- 

 jurious but are lieneficia]. 



A GERMAN APPRECIATION OF THE RUBBER CONFERENCE. 



. Dr. Dannertli. the Honorary Secretary of the Third Inter- 

 national Rubber Conference held in New York last Septem- 

 ber, recently received a communication from the Royal 

 Testing Station in Berlin, Germany, signed by .A. Martens, 

 director of the station, in which the following very pleasant 

 paragraph occurs: 



; "According to the reports of the members of this Station, 

 you rendered them, on the occasion of their study-trip to 

 America, such kind and valuable assistance that the director 

 wishes to assure you of his personal appreciation of this 

 courtesy." 



The Station was represented at the Conference by Dr. Hin- 

 richsen and Ingenieur Memmler. This is one among manj' 

 demonstrations of the fact that the International Conference 

 was conducive to much friendly feeling on the part of rubber 

 men who attended it from abroad. 



USE OF FILLERS VOIDING TIRE GUARANTEES. 



.TJie conditions of guarantee adopted at the recent meeting of 

 tire manufacturers included provisions for the manner in which 

 claims under guarantees would be admitted. One of the clauses 

 is to the following effect : 



"-Any and all guarantees are expressly waived by any pur- 

 chaser of these tires who uses therein any substitute for air ; or 

 who uses them under weights in excess of those for which the 

 various tires are recommended ; or who does not keep tires in- 

 flated to the pressure recommended by us." 



On January 8 the National .Association of .Automobile Manu- 

 facturers passed the following resolution : 



"That members of this association will withdraw from their 

 warranty all cars in whose pneumatic tires there has l)een any 

 substitution for the usual air cushion." 



