Development of fibre properties in mill scale: high- and low consistency refining of thermomechanical pulp (part 2) – Importance of fibre curl

Increased knowledge on the correlation between pulp processing, fibre-properties and paper properties is required to improve fibre-based products. Part 1 of this investigation deals with the effects of HC and LC refining on fibre properties development. LC refining reduced curl and increased tensile index in a manner similar to hot disintegration whereas HC refining increased curl slightly. In this second part, the correlation between fibre curl and handsheet properties of thermomechanical pulp, subjected to low consistency (LC) refining and hot/cold disintegration is examined. Fibre curl decreased by laboratory disintegration and LC refining and showed a linear correlation with increased tensile index and tensile stiffness. Evaluation of fibre property distributions gave a more detailed description of the development of fibre properties. These revealed that disintegration and LC refining gave different fibre curl versus fibre length distributions, even when their average values were similar. These results confirm that analysing fibre property distributions contributes to a more detailed knowledge of the development of pulp quality. Hot disintegration before laboratory testing exaggerated pulp quality and increase internal fibrillation and can therefore be questioned. When hot disintegration is performed before pulp analyses, the impact of LC refining on paper properties may be misjudged.