Effect of compressive and abrasive refining on structural changes in fiber and paper properties

Abstract

The objective of this master’s thesis is to explain the differences in refining action and refining results between compressive and fibrillating refining types. Another aim of this work is to find out the relationship between structural changes in fiber and paper properties.

Softwood pulp samples were refined by Voith LR40, Lampén mill and MASUKO Super Masscolloider. Then fiber structural changes resulting from refining were investigated. External fibrillation, fiber curl and fines were evaluated by Kajaani fiber analyzer apparatus. Internal fibrillation was evaluated according to the degree of Fiber saturation point (FSP). Other fiber and pulp properties were also studied including water retention vale (WRV), Schopper-Riegler (SR), and Zero-span breaking strength. After that effect of refining action on structural changes was determined. Paper properties were then examined which consist of strength, optical, structural and surface properties. Finally, the relationship between structural changes in fiber and paper properties was analyzed.

The study found that Lampén refining, representing compressive refining, highly promote external fibrillation, internal fibrillation, fiber straightening and somewhat shorten fibers. On the other hand, Voith refining, representing combination of abrasive and compressive refining, was found to highly promote external fibrillation, fiber straightening but moderately fiber shortening and develop internal fibrillation. Furthermore, internal fibrillation was found to largely promote most of paper strength properties and have a moderate impact on surface and structural properties while external fibrillation and fine greatly affect structural and surface properties.