XPS analysis of model p-aramid compounds and poly ( p-phenylene terephthalamide) fibers

Abstract

X-ray Photoelectron Spectroscopy (XPS) has been used to determine the surface composition of model p-aramid compounds and a number of poly ( p-phenylene terephthalamide) fiber samples subjected to a variety of commercial and laboratory surface treatments. The surface compositions determined usinf XPS are in accord with the the thermodynamic results of a previous gas adsorption study of the same fibers using Inverse Gas Chromatography (IGC). In particular, the XPS results show that a phase transition detected by IGC in a removable surface layer on a number of fiber samples is associated with the presence of ester groups in the surface layer. Both the negative entropy of adsorption, - ΔS O A , for alkanes, and the surface concentration of nitrogen are dependent upon the thickness of any surface layer on the fibers. An atomic surface concentration of 10.2% nitrogen was determined from near normal exit angle XP spectra of a laboratory-cleaned fiber sample, in close agreement with the expected value of 11.1%. These results confirm the utility of both XPS and IGC in the study of fiber surface properties.