On the interaction of wood and mechanical pulping equipment .2. Pulp quality

In Part I, the development of pulp fibres and the generation of fines by grinding and refining were shown to be significantly different. The consequences of these differences on the pulp properties are discussed here. There is no single correlation between the fines content of mechanical pulps and their freeness. For an equal amount of fines, the freeness of groundwood is considerably higher than that of refiner pulp. The apparent sheet density of groundwood is higher compared to refiner pulp because groundwood contains fewer and coarser fibres. The quantity and the coarseness of long fibres influence the tear strength. Maximum tear index values of groundwood and refiner pulp and linearly related to the long fibre fraction. The correlation is improved when fibre coarseness also is taken into account. The scattering coefficient of all mechanical pulps, irrespective of pulping method, is uniquely related to the amount of fines in pulp.