Pulp bleaching 266 INDEX

Kraft Liner (115-440 g u ). This covering paper is made of at least 80% kraft pulp, bleached or unbleached, and has a bursting strength per basis weight (bursting index) of 3.43 kPa m g h... 

Bleached cotton stalk pulp is treated with different concentrations of ethylene diamine (50-100%) for 20 min. It is clear that the crystallinity index (CrI) of these treated pulps is decreased by increasing the concentration of ethylene diamine that is, the decrystallization increases. The degree of polymerization is nearly the same, but some increase is shown in the sample treated with 100% ethylene diamine. This indicates that 100% ethylene diamine may act as a dissolving agent for low degree of polymerization (DP) of cellulosic chains and hemicellulose. 

All fibers, even bleached ones, seem to have some resinous, hydrophobic material on their surfaces. This material is usually referred to as pitch. We have investigated a bleached sulphite pulp. To remove some of the pitch the pulp can be extracted with ethanol. If, on the other hand, the pulp is heat treated (105 °C 3 h) the pitch is believed to spread over the surface. We made partition experiments for fines fractions from these pulps. A bleached sulphite pulp is of course hydrophilic and all samples partition towards the dextran phase in the basal system. On addition of 0.2 ml 5% P-PEG the hydrophobicity index is 0 for the untreated fiber, for the ethanol extracted fines it is -9 and for the heat treated +5. These results are thus entirely in accordance with our expectations. 

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