Changes in Cell Wall Structure during Kraft Processing of Pinus radiata

Abstract

Comparison of industrial and laboratory pulps from Pinus radiata showed higher energy requirement and lower tear index at the same tensile strength in the case of industrial pulps. Chemical differences between pulps were negligible and cannot explain the strength differences observed. Morphology of the fibers changed during processing with an increase in kinks and curls for industrial pulps. Increased twists and wrinkling in mill fibers were observed based on scanning electron microscopy images. Results from water retention value and fiber saturation point measurements showed reduced water holding ability of industrial fibers. Simons’ stain and hydrogen nuclear magnetic resonance confirmed a higher proportion of macropores in the fibers of industrial compared to laboratory pulps. Evidence supports the presence of both micropore closure and creation of new mesopores and macropores during industrial processing. A combination of fiber damages, porosity changes, and induced deformations seems to play the main role in the lower strength properties of industrial pulps when compared to laboratory pulps.