INFLUENCE OF CATIONIC STARCH ADDITION ON PRINTING GRADE PAPER FORMATION

Influence of cationic starch (CS) on the quality of printing grade papers made with Portuguese pulps was investigated. Paper sheets made with a mixture of bleached kraft pulps from Eucalyptus globulus and Pinus sylvestris (85% and 15%, respectively) were prepared, either in the absence or presence of CS as a dry strength additive. Cationic starches (CSs) with different substitution degrees (DS) (0.017, 0.034 and 0.06) and 3 levels of addition were used (1,2 and 3%, with respect to oven-dried pulps). As expected, CS granted better mechanical properties of the paper samples, yet paper formation was negatively affected by the increased amount of CS. Quantitative formation parameters were determined with a technique based on image analysis by light transmission. First- and second-order entropy, contrast and homogeneity were determined, and their relevance on paper quality quantification was ascertained. The method allowed, too. determination of flocks' size and their distribution, showing that they significantly depended on the added quantity of CS, as well as on its DS.