Pulp refining is a mechanical treatment of fibres using special equipment to initiate changes in structural and electro-kinetic characteristics, which lead to the improvement of the fibre quality. The nature and intensity of the fibre changes depend on several factors, including wood species. The objective of this study was to assess the impact of pine wood species to their processability during pulp refining. Two pine wood species lodgepole (Pinus contorta) and Scots (Pinus sylvestris) pines were mechanically treated and differences in fibre properties between pines were compared and estimated. A strong and significant correlation between the time of mechanical treatment (PFI mill beating for 5, 10 and 15 min) of pulp (Shopper-Riegler number and water retention value), and mechanical, optical, and surface paper properties were found. Higher refining grade and better water retention value and mechanical properties of paper were recognized in the case of lodgepole pine. Also, paper of beaten lodgepole pine fibres had better air permeability and surface smoothness. Light scattering and ISO brightness were higher for Scots pine; there was no difference between species in light absorption.

Keywords: fibre refining; paper properties; paper optics; water retention; air permeability.