Applications of ESCA to polymer chemistry. Part VI. Surface fluorination of polyethylene. Application of ESCA to the examination of structure as a function of depth

Abstract

Molecular core binding energies have been measured by ESCA for series of surface‐fluorinated high‐density polyethylene films. Detailed analysis of the results shows that the technique can be used to establish a comprehensive picture of the early stages of the surface fluorination process. Both the depth of fluorination, and stoichiometry and molecular structure as a function of depth, in the range 0–50 Å have been established. In addition, minor features such as oxidation, hydration, and hydrocarbon contamination at the surface are clearly revealed. Detailed consideration of the results allows a discussion of the dynamics of the overall fluorination process.

Structure and composition of the surface layer in polymers modified by elemental fluorine

“…C A F is an integrated parameter, equal to the amount of fluorine per unit of area of the sample surface that is added to the polymer by substitution, addition, and degradation reactions. 4,9,17 Each of these reactions influences the modified films in a specific manner. Substitution and addition reactions give rise to the surface layer, whose nature and properties resemble those of Teflon, whereas degradation processes should degrade the mechanical properties of the films.…”

“…The vessel was evacuated to a residual pressure of 1 Torr, the polymer films were maintained under this pressure for 30 min until the fluorine and reaction products desorbed from the films, the vessel was filled with air up to atmospheric pressure, and the polymer films were extracted from the vessel. Unlike the previous study, 9 in which the fluorination of polymer films was conducted in a flow of the gas mixture, in this work, the films were fluorinated under static conditions. This made it possible to attain a much more uniform modification of the surface of the films located in the various parts of the reaction vessel.…”

“…10 Mixtures of fluorine and helium of various concentrations were taken from different steel cylinders. In this work, no attempt was made to determine the purity of the fluorine; however, as shown by previous studies, 9 the concentration of commercial fluorine is not less than 98%; the basic impurities are hydrogen fluoride, oxygen, and traces of water. During the preparation of the fluorine-helium mixtures, fluorine was passed through KF for the removal of HF; the traces of water were removed by freezing.…”

“…The composition of the modified surface layers was studied with X-ray photoelectron spectroscopy (XPS; XSAM-800, Kratos, Manchester, UK), 9 IR spectroscopy (IRS-29 spectrometer, Lomo, St. Petersburg, Russia), and elemental analysis. 13 The composition of each film as a whole was determined with elemental chemical data; the degree of modification was calculated as the weight of fluorine that reacted with the polymer (C F ) divided by the surface area of the film (A): C F /A ϭ C A F (the heterophase reaction proceeded only from the surface of the film).…”

Synthetic pulp fiber ozonation: An ESCA and FTIR study

“…X-ray photoelectron spectroscopy or electron spectroscopy for chemical analysis (ESCA) involves the measurement of binding energies of electrons ejected by ionization of atoms with a monoenergetic beam of soft X-rays. It has been already used for the surface characterization of wood, 12,13 wood pulp fiber, [14][15][16] textiles, 17*" cellulose, 15,19 and polym e r~~~-~~ such as films preirradiated with UV radiat i~n ,~~ PE film modified by halogenated gas,25 and PET film grafted with poly (acryl amide) . 26 Infrared spectroscopy has been extensively used in the characterization of cellulose, 27*28 lignin, 29930 and polymer^.^^,^^ In recent years, with the advent of FTIR spectroscopy, surface sensitivity has improved but not as much as with ESCA.…”