Hydrodynamic specific surface area: The Dresden method and its results for pulps affected by different additives

Hydrodynamic specific surface area and compressibility are suitable parameters to characterize the behavior of fibrous material in draining processes such as sheet forming and pressing as well as the strength of the resulting sheets. Obvious data differences caused by effects of raw material or pulping processes made the hydrodynamic specific surface area becoming a parameter of interest in investigations of alternative additives based on commercial products from bio-based industries. The experiments and discussion presented in this paper were part of a Master Thesis with the objective to assess the impact of different, alternative papermaking additives on paper web dewatering intensity in the wet-end part of paper machine with a clear focus on the influence and the role of additives and fibers. Alternative bio-based additives which can be used as a valuable papermaking additive without negative effect on paper quality were targeted. The effect of those additives on the dewatering behavior of pulp suspensions with different papermaking alternative additives using process effects, and correlations between different dewatering methods were studied. The hydrodynamic specific surface area and compressibility parameters made clear distinctions between the applied alternative bio-based pulps, which could improve the dewatering of the mixed pulp slurry to a certain extend. The interactions between the pure reference made from recovered fibers and the character of the alternative pulps, described by properties such as e.g. dimensions, dimensional distribution, moisture content, and chemical composition, have a high variability. The results show that not always the optimal trial parameters could be applied, but at least some of the alternative materials such as the sugar-based Betacal, the wooden sawdust, but also deinking sludge have a potential to adjust suitable dewatering properties for certain base pulps. Additionally, citrus pulp and probably also potato peelings have a chance for application in this sense.