Characterizing the Surface Roughness of Thermomechanical Pulp Fibers with Atomic Force Microscopy

Summary Loblolly pine, separated into mature and juvenile portions, was refined at various pressures (4, 8 and 12 bar). Fiber surfaces were investigated using a Scanning Electron Microscope (SEM) and an Atomic Force Microscope (AFM). Refiner pressure had a significant effect on the fiber surfaces. SEM images showed an apparent increase in surface roughness with increased refiner pressure. This was shown quantitatively with data from the AFM that was analyzed using 5, 2.5 and 1.25 μm scan sizes. A scan size of 2.5 μm was found to be the most informative in terms of quantifying the effect of the different treatments on the two fiber types. The calculated surface roughness was greatest at 8 bar for both wood types. Juvenile fibers in general had higher surface roughness values than mature fibers. The results suggest that refining pressure may influence the failure mechanism of juvenile and mature wood differently.