MaRC! 



i9;:>.i 



THE INDIA RUBBER WORLD 



295 



Himebaugh, British-American Manufacturing Co.; George A. 

 Luddington, The Fisk Rubber Co.; George A. Daum, Pennsyl- 

 vania Rubber Co. 

 The closer contact resulting from tlir KuM.rr Commitice was 



Flutter \'alve Leakage-testing Apparati 



evidenced by a better appreciation on tlie part of the manu- 

 facturers of gas defense needs and this was reflected in better 

 deliveries of rubber pans. By February, production had reached 

 a firm basis and in the three succeeding months the quality of 

 production was improved to such an extent that rejections at the 

 assembly plant were reduced to a very low percentage. 



RUBBERIZED FABRIC EXTENSIVELY USED. 



Rubberized fabrics were extensively used in mask manu- 

 facture and upwards of 1.500,000 yards were made. In the early 

 days many difficulties were encountered and specifications were 

 changed several times before a satisfactory gas-proof fabric was 

 obtained. 



At first a Xo. 4 sail-cloth coated on one side with rubber was 

 used. The amount of rubber was insufficient and many masks 

 were unsuitable on account of light spots and even pinholes. To 

 overcome this, more rubber was used and both sides of the 

 fabric were coated. With one ounce per square yard of rubber 

 on the outside, 3.6-ounce sail-cloth and 4-ounce rubber on the 

 inside, there was a total weight of 8.6-ounces per square yard. 

 This, however, still resulted in light spots which were a cause 

 of concern to the Service. At the same time it was reported from 

 abroad that the Germans were using a new tear-producing gas, 

 chloropicrin, which had great power in penetrating rubber and 

 consequently with thinly coated fabrics might soon put soldiers 

 out of action. Steps were therefore taken to increase the rubber 

 coating and by compounding research to find a combination, if 

 possible, which would better resist the gas. Hundreds of com- 

 pounds were produced and tested and it was found that paraffine 

 in small quantities incorporated in the rubber was most useful 

 in increasing resistance. 



FABRIC TESTING METHODS AND APPARATUS. 

 The method of testing employed at first consisted of putting a 



thin glass-sealed capsule of the poison liquid (chloropicrin, boil- 

 ing point, 122 degrees C.)^ in a wide-mouthed 2S0-cc. bottle, 

 covering the mouth of the bottle with one layer of the fabric to 

 be tested, breaking the capsule and noting the time for the gas 

 to make itself evident to the eye or nose. This method was 

 unsatisfactory for two reasons— difference in sensibility of the 

 observers, and marked effect of temperature on the rate of 

 permeability. This method was replaced by one worked out by 

 the Bureau of Mines which gave much more consistent results. 



The apparatus consisted of a silvered, two-part drum in the 

 lower half of which was placed the liquid chloropicrin, the fabric 

 to be tested acting as a diaphragm between the upper and lower 

 halves, the upper half being provided with an arrangement for 

 sweeping air over the upper surface of the fabric. The air was 

 swept out through hot tubes which served to break down any 

 chloropicrin to chlorine as soon as it came through. This end 

 point was made evident by the use of starch iodide solution. 

 While this apparatus provided an accurate end point and 

 temperature control of the chloropicrin, it did not provide for 

 temperature control of the incoming air and, therefore, the 

 temperature of the fabric. The importance of this was not re- 

 alized until summer when the permeability number of given 

 fabric specifications went down markedly. The apparatus was 

 finally modified by the Gas Defense Division to provide ample 

 thermostatic control of liquid and fabric and thoroughly consist- 

 ent results were then obtained. 



The early requirements for fabric to test 8 minutes against 

 chloropicrin were soon raised to 17 minutes. At this period it 

 seemed likely that fabric with resistance of one hour might be 

 demanded at any moment by the use on the part of the Germans 

 of even more penetrating gas. It was recognized that this re- 

 quirement could be met by increasing the amount of rubber 

 coat, but this plan suffered two drawbacks — one, a too great in- 

 crease in thickness and stiffness of the cloth, and the other, the 

 reriuiremcnt of too long a time for aeration. This latter term 

 may be explained by the fact that permeation of rubber by these 

 gases was a solubility phenomenon, layer by layer, through the 

 rubber film. A thicker rubber which required one hour for the 

 gas to penetrate required a correspondingly long time for the 

 gas absorbed in the rubber to dissipate by evaporation. As a 

 practical result, the soldier might be protected against a gas 

 attack, put bi^ mask au.i\ in his knapsack and later, when 



wearing his mask, actually sufl:'er a gas attack from the mask it- 

 self as the gas evaporated from it. 



THE DEVELOPMENT OF FABRIC SPECIFICATIONS. 



It was at this time, therefore, that the greatest amount of 



research work on fabric was performed by the three rubber 



companies who were making masks. As an outgrowth of this 



