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Abstract
Fibers tilted in z-direction by hydraulic forces associated with rushing or dragging the sheet can bond multiple strata together, resulting in improved out-of-plane shear strengths. Tilted fibers are difficult to identify microscopically; however, their presence can result in different measurements of Scott internal bond when tests are carried out in the two opposing machine directions. These tests identified differing fiber tilts that correlated with differing amounts of out of-plane shear strengths in three otherwise comparable linerboard samples. The effect was duplicated in handsheets in which stiff, non-bonding carbon fibers were added to pulp to produce three-dimensional structures that interfered with the tendency of draining fibers to stratify. Even though the substitution of 10% carbon fibers produced a loss of bonding sites, the out-of-plane shear strength of the handsheets improved by an average of 15%. The search is on for methods to control fiber tilt in commercial paperboard. Success will result in improved mechanical performance without additional fiber costs.
Keywords
Orientation,
fibers,
testing,
shear,
optical measurements,
fiberboard,
mechanical properties,
paperboard,
optical properties,
dimensional stability,
stiffness,
pulp,
fiber analysis,
shear strength,
fiber orientation,
fiber properties,
z-direction,
microfibril angle,
linerboards,
bonding,
strength,
fiber tilt,
bond strength,
tensile strength
Citation
Vahey, David W.; Considine, John M.; Gleisner, Roland; Rudie, Alan; Rolland du Roscoat, Sabine; Bloch, Jean-Francis. 2009. Impact of z-direction fiber orientation on performance of commercial and laboratory linerboards. In: PaperCon 2009, TAPPI/PIMA Paper Conference and Trade Show, 2009 May 31-June 3, St. Louis, MO. Atlanta, GA : TAPPI, 2009: [10] p.
