Sulfonation of UHMW-PE fibers for adhesion promotion in epoxy polymers

This paper reports the effects of a controlled sulfonation process using sulfur trioxide in Freon® to treat UHMW-PE fibers in order to improve their adhesion to a thermosetting polymer. Following sulfonation treatment, PE fibers were evaluated by both chemical and physical methods to determine the effectiveness of treatment. Infrared spectroscopy, X-ray photoelectron spectroscopy, titration, and contact angle measurements were used to investigate the chemical pathway of sulfonation on UHMW-PE fibers. The physical effects of sulfonation on fiber topography and strength were investigated using scanning electron microscopy and conducting tensile strength measurements on treated and virgin samples. The effect of sulfonation on adhesion was measured using micromechanical test methods to quantify the level of bonding between sulfonated UHMW-PE fibers and a thermosetting matrix. For comparative purposes, the sulfonated UHMW-PE fibers were compared to plasma and corona treatments. The interfacial shear strength demonstrated an increase in adhesion with longer immersion times in the sulfonating solution which may be an effect of higher levels of mechanical interlocking caused by fiber pitting and etching.