Quantitative surface analysis of hemp fibers using XPS, conventional and low voltage in-lens SEM

Surfaces of hemp fibers with different treatments: (1) as received; (2) water washed; and (3) treated with NaOH, were examined using a combination of conventional Scanning Electron Microscopy (SEM), lignin staining and a novel low voltage in-lens detector SEM technique which provides compositional contrast between polymeric materials on the surface. Surface composition determined using quantitative X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDS) showed that the surfaces of the as received fibers and the water washed fibers were predominantly lignin and extractives and only after NaOH treatments was there sufficient oxygen on the surface to allow for the presence of polysaccharides. Using the in-lens backscattered SEM technique, spatial distribution of polymeric materials on the surface was shown to be highly non-uniform. The findings have implications for design of natural fiber composites and the interfacial properties between fiber and matrix