Excimer laser surface modification of ultra-high-strength polyethylene fibers for enhanced adhesion with epoxy resins. Part 1. Effect of laser operating parameters

The effects of a pulsed XeCl excimer laser (308 nm) on ultra-high-strength polyethylene (UHSPE) fibers and the fiber/epoxy resin interface were studied. SpectraTM 1000 (UHSPE) fibers were treated in air with a pulsed excimer laser with different energy density levels and numbers of pulses. Chemical and topographical changes of the fiber surfaces were characterized using X-ray photoelectron spectroscopy (XPS), dynamic wettability measurements, and scanning electron microscopy (SEM). The fiber/epoxy resin interfacial shear strength was evaluated by the single-fiber pull-out test. The XPS spectra demonstrated that the fiber surface undergoes photodissociation because of the laser treatment, which results in the incorporation of oxygen at the surface. The wettability data showed that the fiber becomes more polar after laser treatment and also more wettable. SEM photomicrographs revealed that the surface roughness of the fibers increases after the laser treatment. The interfacial shear strength (IFSS) results indicated that the laser treatment significantly improves the adhesion strength of UHSPE fibers with epoxy resin. This enhancement in IFSS is attributed to the increased roughness of the fiber surface and increased interfacial area, increased polar nature and wettability, as well as the improvement of the acid-base component of the surface energy after laser treatment.