Document NGx7jvmZJyaMMjOZ7p060jyZQ

Inter - organization Correspondence R. W. Strassburg riKLD POINT on A MOON DCPAftTMCNT ft OkOO. NO. Akron; Bldg. WHB-4; Dept. 0001 M. M. O'Mara rtiLo point on AKnoN okpantmcnt ft ncoo. no. Avon Lake Technical Center Diffusion of Air-VCM Through Plastic Work Suits REGoodrich oatc rouR lcttcp uatt this t i ew August 22, 1974 Introduction You submitted two production work suits to our laboratory for measurements on the diffusion of VCM through these protective suits. One was a yellow material consisting of plasticized PTC; the other was a white material, identified by J. W. Ryan,of our infrared laboratory, as a polyethylene coated composition. Approach As an initial approach we used an existing piece of equipment which was designed to measure the transport rate of gases through plastic membranes. The method is an ASTM procedure (D 1434-63) and is called "Gas Transmission Rate of Plastic Film and Sheeting". The method is based on Pick's law: 1 * t where q gas transport rate p = proportionality constant referred fo as the -- permeability constant A = area of the sample t = thickness of the sample Ap = pressure differential across the membrane In the ASTM method, la usually determined as a function of temperature. In this way an Arrehnius plot can be determined and the energy of activation of the permeation process can be made. In terms of the problem at hand, this type of data (i.e. activation energy) is not suitable. Absolute transport data are required to answer the questions relating to the use of these suits in the field. We therefore determined diffusion (i.e. transport) rates as a function of pressure for the two materials submitted by you. Procedure The ASTM D 1434-63 method was followed using the Permeability Console Model CS-135. A 1.0 mm diameter capillary tube was used for measuring gas permeability. All measurements were mada at 23*C. using a 152ppm vinyl chloride in air standard. All test samples were 9.97 in. in area. BFG23172 mro iw m acv. m m lit no. m u.a.A. 22927001 R. W. Strassburg Page Two August 22, 1974 Results (A) white polyethylene coated material Gas transport was so rapid through this material at Ap = 1 lb./in.2 that meaningful measurements could not be made. This material should not be considered a "protective" device. (B) yellow plasticized PVC coated matpr-tal The following diffusion rate data were collected at the following pressures (Ap): AP, lbs./in.2 ,(2)Diffusion Rate (cm^/sec.)^ 9.97 in. 2 area 3402 in.2 20 0.86X10"4 0.029 30 1.15X10"4 0.039 58 2.19X10"4 0.075 (^not corrected to S.T.P. (2)this is the approximate area of the entire suit A plot of the data ia shown in Figure 1. 22927002 BFG23173 22927003 3 R. W. Strassburg Page Four August 22, 1974 Discussion It should be noted from Fick's law that a pressure differential must exist before diffusion will take place. The pressure differentials shown in the data table and in Figure 1 range from over 1 atmosphere to about 4 atmospheres. Even at this higher value, the diffusion rate of the standard gas through the entire suit is 0.075 cc/sec. Assuming that the VCM in the air standard migrates at the same rate as the air (it is probably lower) then the absolute amount of VCM migrating into the suit over a 7 hour day is 0.287 cc (0.734 mg). Under normal operating conditions there will be no diffusion of vinyl chloride through this protective suit. Future Testing It is obvious that this type of test offers an excellent method for screening potential candidates for use as a protective covering. A quick field test can also be carried out which will screen out those materials which are not impervious to air migration. I noticed that one could actually breathe (with difficulty) through the white polyethylene coated material. If a material cannot pass this test then it should not be considered for further evaluation. Flanmabilltv One of the serious problems with any of these materials is their inherent flanmability. Generally they burn much more rapidly and generate more heat than normal work cloching. Unmodified polyethylene on unmodified cellulose should not be tolerated under any conditions as wearing apparel. I suggest that all candidates be submitted to our laboratory for fabric flammability testing. Testing requirements are six 14" X 4" samples. If stitching is present in the suit, the six test specimens should include the stitching along the vertical. ch cc: B. A. DiLiddo A. L. Schultz F. E. Krause E. G. Scbwaegerle L. B. Crider R. J. Fawcett E. W. Harrington M. N. Johnson E. B. Katzenmeyer, Jr R. M. Kreager J. L. Nelson G. D. Schaaf R. D. Scott H. Waltemate W. J. Wilcox B. M. G. Zwicker M. M. O'Mera BFG23175 22927004 T