Authors: Mimi Y Keating Jon L Howell
Publish Date: 2011/05/01
Volume: 106, Issue: 1, Pages: 213-220
Abstract
Decomposition has been studied in the chemistry of perfluoropolyethers PFPE thus far no molecular structure information is reported TGMS is a tool to follow the off gassing of decomposition for clues We selected two PFPEs that have different properties Krytox® XHT1000 and Fomblin Z60 heating to normal decomposition and catalytic decomposition in the presence of alumina powder Comparing the decomposition fragment intensities the molecular structure of the branched Krytox® XHT1000 oil is more stable than the blocky Fomblin Z60 We see aluminumcontaining fluorine fragments in the rapid decomposition of oils in contact with alumina powder It has been suggested the formation of AlO6−n F n where n = 1 2 and 3 in which the fluorine atoms are selectively associated with aluminum atom The major decomposition products are small and large fragments of fluorocarbons and perfluoroalkoxy In the absence of alumina powder Krytox XHT1000 shows only a loss of 13 mass/ after several hours at 330 °C whereas in the presence of 1 mass/ alumina powder the oil has rapidly decomposed to 67 mass/ of its original mass within 15 min Fomblin Z60 a product might not be designed for high temperature exposing to the same conditions at 330 °C for several hours and shows a loss of 98 mass/ alone but in the presence of 1 mass/ alumina powder shows a loss of 98 mass/ in 36 min When 3 mass/ of two new developmental additives were added to the both oils the catalytic decomposition in the presence of 1 mass/ alumina powder was significantly reduced in Krytox® XHT1000 showing only a loss of 23 mass/ in 4 h but nearly all weight for Z60 in 60 min In the oil grades that contain the new additives we see the fragments of Al–O–S and F–Al–O–S The sulfurcontaining compound has been reported ionically bonded to oxide in a tripod configuration of alumina surface which shields the formation of Al–F
Keywords: