Surface Characterization of PPTA Fibers Using Inverse Gas Chromatography

This work concerns the surface characterization of poly(p-phenylene terephthalamide) (PPTA) fibers, either with or without finish, and submitted or not to washing with acetone or to oxygen plasma treatment. These materials were studied by inverse gas chromatography (IGC) at infinite dilution using nonpolar (C6−C12 n-alkanes) and polar molecules with different acid−base characteristics (tetrahydrofuran, toluene, carbon tetrachloride, acetone, tert-butyl alcohol). Complementary information was obtained by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Results showed that the presence of a standard finish strongly decreases the surface energy of the PPTA fibers and confers them a more acidic character. Surfaces similar in structural and chemical properties to those of the pristine fibers can be obtained by solvent washing. Oxygen plasma treatment of PPTA produces strong changes in adsorption energetics (indicative of pore formation) and in surface nanomorphology, globular-like structures being formed. At the same time, an increase in the number of acidic and basic sites, identified as oxygenated functionalities (especially alcohol/ether groups), was detected. The capability of the used methodologies, particularly IGC, to follow changes in the surface properties of polymeric fibers is highlighted.