EFFECTS OF MECHANICAL AND CHEMICAL TREATMENTS ON THE PORE-SIZE DISTRIBUTION IN WOOD PULPS EXAMINED BY INVERSE SIZE-EXCLUSION CHROMATOGRAPHY

The inverse size-exclusion chromatography technique (ISEC) has been ad apted with a column packing procedure which allows virgin, never-dried wood pulps to be examined for effects of different mechanical and che mical treatments on the fibre swelling (pore volume and pore-size dist ribution). The reproducibility was high (+/-2-4%) for chemical pulps, and satisfactory (+/-4-8%) for mechanical pulps. Effects of beating, l ignin content, recycling and the nature of the counter-ion on pore-siz e distribution were studied. The new technique allowed a better and mo re complete understanding of how pore sizes were affected by the diffe rent treatments. The apparent pore-size distribution shifted from main ly small pores in an untreated TMP pulp, towards larger pores with a l ower proportion of smaller pores for an unbleached kraft pulp. This tr end was even more pronounced for a bleached kraft pulp. Recycling of p ulps caused irreversible partial pore collapse.