Tests for Z-direction fiber orientation

Abstract

Fibers that acquire a Z-direction tilt in the forming process help bond adjacent strata of the paper sheet, increasing Z-direction shear and other properties. For certain tests, this manifests itself as a test difference upon 180° in-plane rotation of the sheet. Seven of eight different paper grades ranging in grammage from 73 to 268 g/m2 were found to show this difference for Scott internal bond tests, directional brightness tests, or both. Directional effects were compared using an extensional and a shear metric. One-third of comparisons showed significant directional effects at the 75-100% confidence level, including roughly equal numbers of Scott bond and brightness comparisons. However, the two tests did not reinforce each other strongly; agreement regarding directional effects occurred in only 60% of comparisons. The number of significant effects in the cross-machine direction matched those in the machine direction (MD), suggesting a more complex model may he needed. The best support for the fiber-tilt model was in the case of MD Scott-internal-bondtesting.

Citation

Vahey, David W.; Considine, John M. 2007. Tests for Z-direction fiber orientation. 61st Appita Annual Conference and Exhibition : Gold Coast, Australia, 6-9 May 2007 : proceedings. Carlton, VIC : Appita, c2007: ISBN: 9780975746928: Pages 53-59