Adhesion characteristics of oxygen plasma-treated rayon fibers

The effect of oxygen plasma treatment of fiber on the adhesion between regenerated cellulose fiber and polyethylene (PE) was investigated using the single-fiber fragmentation test. In addition to allowing the determination of the interfacial shear strength, the fragmentation test provided a great deal of useful information on shear stress transfer and failure mechanisms in the systems. It was found that oxygen plasma treatment considerably enhanced the interfacial adhesion, as established by both the shear strength values that were measured and the birefringence patterns observed. The influence of the duration of treatment on adhesion was studied and found to be a very important parameter. The roles of surface chemistry, surface energetics, and surface topography of fiber in the interaction balance were investigated using electron spectroscopy for chemical analysis (ESCA), contact angle measurements, and scanning electron microscopy (SEM). It was seen that neither the plasma-induced changes in the surface energetics nor those in the surface topography could have exerted a positive effect on adhesion. Instead, the improved adhesion was ascribed to covalent bonds formed between the fiber and the matrix, as hydroperoxides, which were created on the fiber surface by the plasma treatment, decomposed during the fabrication of single-fiber specimens.