Abstract
Inverse gas chromatography has been used to measure the surface adsorption of alkane vapors on a series of cleaned poly( p-phenylene terephthalamide) (PPTA) fibers, commercially known as Kevlar 49. From the retention volumes at infinite dilution over a range of temperatures, the differential heat of adsorption, ΔH A o, the standard free energy of adsorption, Δ G A o, and the standard entropy of adsorption, Δ S A o, have been determined for the n-alkane vapors C 6C 10 on the various substrates. The London (dispersive) component of the surface free energy, γ s d , has also been calculated. Comparison of results for the original materials with those of the cleaned samples has allowed the evaluation of surface contamination and the effectiveness of a range of solvent extraction procedures. Low values of − ΔH A ̊ , γ s d , and − ΔS A ̊ were obtained for alkane adsorption on the original materials, indicating significant levels of surface contamination. These contaminants were removed by solvent extraction with acetone or water. The subsequent changes in ΔH A ̊ , γ s d , and ΔS A ̊ revealed that higher energy adsorption sites of the highly crystalline PPTA fibers were now exposed.
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