Mechanical Pulp Fines: Effect of Particle Size and Shape, 1997 Papermakers Conference Proceedings

The effect of different types of particles on the properties of the whole fines fraction and on the paper properties was studied. Fines particles of two totally different categories, fibrils and flakes, were prepared and their effect on handsheet properties was studied. The fibril fraction consists of fibrillar material, i.e. ribbon-like and thread-like particles. The flake fraction consists of flake-like material, i.e. cell wall and middle lamella fragments, thick lamellae and ray cells. An advanced image analysis method was used to characterise the properties of fibrils and flakes. The results of the image analysis showed the role of the fibrils and flakes of different sizes for determining the properties of whole fines and subsequently produced paper. The results demostrate that the fibril and flake fractions have distinctly different characteristics and effects on sheet properties. The fibrils are strongly responsible for the strength properties while the flakes improve light scattering. It is proposed that the fibrillar content could be one basic property of mechanical pulp fines.