Accession Number : ADA310450
Title : Degradation and Crosslinking of Perfluoroalkyl Polyethers Under X-Ray Irradiation in Ultrahigh Vacuum.
Descriptive Note : Technical paper,
Corporate Author : NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CEN TER
Personal Author(s) : Mori, Shigeyuki ; Morales, Wilfredo
PDF Url : ADA310450
Report Date : MAR 1989
Pagination or Media Count : 16
Abstract : Degradation of three types of commercially available perfluoroalkyl polyethers (PFPE)-Demnum S200, Fomblin Z25, and Krytox 16256-by x-ray irradiation was studied by using x-ray photoemission spectroscopy (xps) and a mass spectrometer under ultra-high-vacuum conditions. The carbons in the polymers were characterized by chemical shifts of C sub 1s binding energies. Gaseous products containing COF2 and low-molecular-weight fluorocarbons were formed. From Fomblin Z25, which has acetal linkages (-OCF2O-), a large quantity of COF2 gas was evolved. Liquid products became tacky after a long irradiation time, and some did not dissolve in Freon. High-pressure liquid chromatography (HPLC) showed that molecular weight distribution became broader and that higher molecular weight polymers were formed from Demnum and Krytox. We concluded from these results that degradation and crosslinking took place simultaneously. Demnum crosslinked more easily than the other fluids. The time dependence of both xps spectra of C sub 1s and mass spectra showed that C-O-bonded carbons in PFPE's were removed faster than other carbons. There was no substrate effect on the degradation reaction because the first-order rate constants calculated from the change of gaseous products were similar when stainless steel (440C) and gold-coated surfaces were used. Metal fluorides were formed on stainless steel during the reaction. A mechanism for the degradation of PFPE's is discussed on the basis of their molecular structures.
Descriptors : *DEGRADATION, *CROSSLINKING(CHEMISTRY), *X RAY PHOTOELECTRON SPECTROSCOPY, *IRRADIATION, *FLUORINATED HYDROCARBONS, *ULTRAHIGH VACUUM, TIME DEPENDENCE, DISTRIBUTION, POLYMERS, MOLECULAR WEIGHT, STAINLESS STEEL, HIGH PRESSURE, METAL COATINGS, SUBSTRATES, GASES, SURFACES, LIQUID CHROMATOGRAPHY, FLUIDS, MOLECULAR STRUCTURE, MASS SPECTROMETERS, GOLD, LINKAGES, FLUORIDES, ALKYL RADICALS, POLYETHERS, FLUORINE COMPOUNDS, CHEMICAL SHIFTS, MASS SPECTRA, ACETAL RESINS.
Subject Categories : Polymer Chemistry
Atomic and Molecular Physics and Spectroscopy
Distribution Statement : APPROVED FOR PUBLIC RELEASE