Example 1
1 pound PTFE regrind, obtained from CSI Plastic (Millbury, Mass.), was inserted into a chamber. The chamber was heated using annular flow of hot oil at 200° C. for a nominal chamber temperature of 175° C. Oxygen was removed from the chamber using a nitrogen pressure swing inerting method. Gas flow of 20 vol % fluorine and 80% nitrogen was started at 0.4 scfm. The chamber pressure varied between 5 PSIA and 12 PSIA over the course of the experiment. The fluorine gas was fed through the chamber for 4 hours with the direction of gas flow alternated between top to bottom and bottom to top each hour. The amount of fluorine used was 4.99 pounds of fluorine per 1000 pounds of PTFE regrind. At the end of 4 hours, the oil heat was turned off and the chamber was again inerted using a nitrogen pressure swing method. Atmospheric air was fed through the chamber until the chamber temperature dropped below 55° C. The sample was tested for perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) using EPA method 3452A and EPA method 8321B. The sample was tested both before and after being treated with fluorine gas. The detection limit for PFOA and PFOS was 100 parts per trillion. No PFOS was detected either before or after the sample was treated. The results are shown in Table 1.
