Document ymNZenoBB52zRLzpbLp2zJo86

APPENDIX 2 AR226-2379 ANALYTICAL TECHNIQUE USED TO DETERMINE C-8 CONCENTRATION IN AQUEOUS SOLUTION The basis for the analytical technique used to determine the C-8 concentration in an aqueous solution was Polymer Products Department method Code No. T 212.2000 (revised 8-7-81). The referenced method is for the determination of equivalent C-8 dispersing agent in FEP aqueous dispersion. By using the method with and without the addition of an aliquot of an unknown C-8 sample, is was possible, by difference, to determine the concentration of the unknown C-8 sample. The following is a description of how the method was adapted for use* A 'large' source of aqueous FEP dispersion was obtained for use in this analysis. The dispersion was stored in a plastic container until needed. Vhen used, the dispersion was gently mixed and then filtered through 'cheese cloth' to remove large pieces of coagulated dispersion. The filtered dispersion was used for all samples for the day's analyses. For purposes of this technique, 10 +/- 0.01 grams of FEP dispersion used, made up to 100 ml vith demineralized water using a graduated cylinder. The equivalent C-8 concentration in the FEP dispersion was determined using Method T 212.2000. This concentration was considered the 'blank'. In actual usage, only the volume of CTMAB (cetyltrimethylammonium bromide, 1.0 gm/Iiter) required to coagulate the FBP dispersion was recorded. A second measurement was made, similar to the first, but where a measured volume of the unknown C-8 solution was added to the FEP dispersion. In the second measurement, additional CTMAB would be required to complex with the additional C-8 present before the FEP dispersion would coagulate. By difference (the amount of CTMAB required for the unknown sample relative to the 'blank'), the quantity of the unknown additional C-8 could be determined and, hence, its concentration. The theory upon which the method is based is that each mole of CTMAB will complex with a mole of equivalent C-8 and that the complex will have no dispersant properites. Vhen sufficient C-8 has been removed from the solution, the FEP dispersion will be destabilized and coagulate. The supernate will be clear after the dispersion 'breaks'. This method requires the laboratorian to determine the point vhen enough CTMAB has been added to the dispersion sample so that the liquid above the coagulated dispersion is clear. This point was not always easy to determine and at times varied between laboratorians. However, within a single day using the same experienced laboratorian, the results appeared to be internally consistent. , RJZ031108 EID179722 APPENDIX 2 2 of 5 Belov is the equation used in this technique: here Cx Vx (Vx - Vb) 431 Cx ------------- x 1000 x --------- Vex 364-48 Concentration (in mgm/1) of the unknown C-8 solution. Volume (in mis) of CTMAB solution required to coagulate the FEP dispersion and the aliquot of unknown C-8 solution. Vb Volume (in mis) of CTMAB solution required to coagulate the FEP dispersion without any added C-8 solution. Vex Volume (in mis) of the aliquot of unknown C-8 solution. 1000 Concentration (in mgm/1) of CTHAB standard solution. 431 Molecular weight of C-B (as ammonium perfluorooctanoate). 364.48 Formula weight of CTMAB. Typical results are shown below: (22.6 - 8.9) Cx ---------------- x 1000 x 4.0 431 ------- = 4,050 mgm/1 364.48 I 'i V=I% RJZ031109 EID179723 APPENDIX 2 3 of 5 E. I. du Pont de Nemours & Co. (Inc.) Polymer Products Department Code Ho. T 212.2000 Revised: 8-7-81 Page 1 of 3 teflon* fep fluorocarbon resin.aqueous dispersion . Equivalent C-8 Dispersing Agent I. Scone and Applications 'FMq method Is applicable to determining the equivalent C-8 dispersing agent in FEP dispersion. II. Principle Percent C-8 is determined by titrating FEP dispersion vith a solution of cetyltrimethylamaonium bromide. III. Interferences 17. Sensitivity. Precision, and Accuracy The precision (sigma) of this test based on five runs made on one sample is 0.0005 vith an X of 0 . 1 2 5 ^ .C-8 . V. Apparatus VI. Reagents * ' 1. Cetyltrimethylammonium bromide (CTMAB), 1 g/liter (RC 190.127) VII. Operating Conditions VIII. Safety and Health Precautions As dispersion or coagulation effluent can contain C-8 , contact vith dispersion should be avoided b y wearing the proper gloves. The current allowable exposure limit for C-8 is below 1 ppb and C-8 is suspected of being teratogenic. IX. Procedure 1. Weigh 25 ( 0.01) g FEP dispersion into a 600-ml beafcer. 2. Add 200 ml (grad cyl) demin water to the dispersion. 3. Stir the beaher using a magnetic stirrer until the dispersion and water are mixed (about 30 seconds). V. Fill a buret with 1 g/llter CTMAB solution. Record the reading. * Reg. U.S. Fat. & Tm. Off. RJZ031110 EID179724 APPENDIX 2 4 of 5 Page 2 of 3 5. Using the buret, add CTMAB solution to the dispersion slowly, with constant magnetic stirring. As CTMAB is added, polymer will begin to coagulate. When it appears that most of thepolymer has coagulated, stop adding CTMAB and then stop agitation a fey seconds later. 6 . Allow the bulk of the polymer to settle out and observe the supernatant liquid. If it is cloudy, resume agitation and add 0.2 to 0.5 m l of CTMAB. 7- Stop agitation and allow to settle. 8 . Repeat steps 6 and 7 until the supernatant liquid i3 perfectly clear. A clear supernatant liquid is the end point of the titration. 9. Record the buret reading. 10. Find specific gravity of the dispersion and percent solids, using -Method T 202.8oU. 11. Calculate % C-8 and g C-8/g TEP. X. Calculations - 1. Calculation of % C-8 mL CTMAB = (step 9 - step b) ' % c-8 = rcE CTMAB r O.IlSh ~ vt of dispersion, g 0 ii8!t = to.0275(Normality of CTMAB)] x l>3l(M.W,)I x 100(iO . -- " 1000 (mg/g) 2. Calculation of g C-8/g F5P % FEP = $ solids (step 10) % C-8 from step 1. Calculation = "|i| Report two significant figures, i.e., .091?. XI. Calibration XII. Notes RJZ031111 EID179725 APPENDIX 2 5 of 5 Code Bo. T 212.2000 Revised: 8-7 -8 1 Page 3 of 3 XIII. References 1. Couture, M. J;, Washington Works Technical laboratory Hotebook Bo. 1026, pp 88-89 ` 2. Plastics Department Laboratory Test Method T 202.8oAo 3. Original Method, Washington Works Technical Laboratory, 3 - U - T 1 1*. First Revision, Washington Works Technical Laboratory, 2-16-76 Revised to reflect the use of C-8 instead of C-9 in FEP polymerization. Origin: Washington Work3 Technical Laboratory, 1st Circulation 5-15-81 Prepared by: C. W. Jones Approved by: D. L. Kerbov Approved by Laboratory Methods Committee, 8-7-81 WW-2989 RJZ031112 EID179726