SINGLE-FIBER WETTABILITY OF HIGHLY SIZED PULP FIBERS

The Wilhelmy technique is used to measure single-fiber wetting propert ies of highly sized pulp fibers. For Douglas-fir fibers treated with v arying amounts of alkyl ketene dimer (AKD) emulsion, the dynamic advan cing contact angle increases rapidly with increasing AKD level. A cont act angle of 90-degrees with water (where hard sizing is expected to b e achieved) is reached at a nominal AKD dosage level of 0.75 kg/ton. E ven though advancing contact angles as high as 130-degrees were measur ed, it was found that the receding contact angle remained at essential ly 0-degrees. This allows determining the advancing angle without the need for separate fiber perimeter measurements. The results indicate t hat, in some production situations, excessive amounts of AKD may be us ed to assure bard sizing. Retained and reacted amounts of AKD were als o determined and found to be significantly lower than, but linear with , the nominal (apparent) AKD dosage.