Characterization of high-yield pulp (HYP) by the solute exclusion technique.

By following the solute exclusion technique, we determined the pore characteristics of 3 hardwood high-yield pulps (aspen, birch, maple). The fiber saturation point (FSP) was 1.40, 1.36 and 1.19 g water/g pulp, for aspen, birch, maple, respectively, which is lower than that of chemical pulps. Different fractions obtained from the Bauer-McNett classifier showed that the HYP fines have much more pore volume than their long fiber counterparts. The effects of beating, drying and re-wetting on the pore characteristics of HYP were also studied. Beating led to increased total pore volumes. Upon drying and re-wetting, much of the small pores from the HYP underwent permanent closure while the big pores were only slightly affected. Finally, the relationship between the water retention value (WRV) and FSP for HYP was examined.