Papermaking quality of fines from different pulps - the effect of size, shape and chemical composition

The fines of chemical pulps have a strong tendency to intensify the interaction between fibres. This is mainly due to the increased density of the network. A sheet made of kraft fines has a remarkably high density, 1100 -1200 kg/m3, whereas a handsheet made of TMP fines has a rather low density, about 450 kg/m3. In this study several pulps were compared. The fines form a spectrum ranging from fines of bleached softwood kraft to the fines of mechanical pulp. The differences between softwood and hardwood kraft fines as well as between bleached and unbleached softwood kraft fines are rather small. Clearly larger differences are within the different fractions of a fines from a certain chemical pulp. In addition to the size of the fines particles the shape seem to be important factor. Only part of differences in the quality of the fines can be explained by the chemical composition. But the results indicate that the size shape and chemical composition of the fines fraction have inter-correlation.