Degradation of polymers subjected to radio‐frequency discharges in SF6

Abstract

AbstractStudies were conducted on the degradation reaction of polyethylene, poly(tetrafluoroethylene), and an expoxy resin resulting from the action of a 13.56‐MHz radio‐frequency (rf) discharge in SF6. The curves showing the temperature variations of the samples during the experiment suggest that this degradation process occurs in two distinct stages: in the first, the heat released by the electric discharge causes the thermal degradation of the polymers, whereas in the second, the volatile degradation products react in the gas phase with the excited SF6. Analysis of the reaction products shows consistency with this two‐step degradation model. The main degradation products have been identified as C2H2, C2H4, SOF2, and CS2 in the case of polyethylene; as CF4, C2F4, and SOF2 in the case of poly(tetrafluorethylene); and finally as CO2 and SOF2 in the case of the epoxy resin. Furthermore, it is interesting to note the formation of polymers of the di(trifluoromethyl) polysulfane type, CF3‐Sn‐CF3, among the reaction products. The more volatile members, n = 2, 3, and 4, were identified by mass spectrometry, whereas the heavier members, identified by infrared spectrophotometry, often took the form of a whitish powder deposited on the walls of the reactor.