Open Access

Jürgen Belle, Stephan Kleemann, Jürgen Odermatt

• Introduction: The initial wet web strength (IWWS) is one of the most important parameters for effective paper machine performance[1]. As previous research has shown, a huge variety of parameters is already known to have an impact on the IWWS [2]. Despite this fact, there is still an on-going discussion on possible explanations for the mechanisms of initial wet web strength development [3]. One fact is that the mechanisms for strength development at low solid contents are quite different from those of dry paper. However up to today it is not clearly defined which forces are addressed to which fibre characteristics at certain dryness levels, and their effect on the IWWS. The goal of this paper is to discuss existing explanation models for IWWS development and to complement these, generating an advanced model by the inclusion of own trial results. Methods: For this study full factorial design of experiments (DOE) [4]was implemented in order to determine the weighting of important factors like dryness level, degree of refining, degree of hornification and conductivity on the IWWS. The goal was to use this DOE-method within the field of paper strength research in order to receive advanced information on the mechanisms of strength development at different dryness levels. The study was carried out with laboratory hand sheets, made of commercial bleached soft wood pulp, which was refined in a laboratory valley beater. The IWWS was measured according to a German standard DIN 54514. Results: The data analysis showed that weighing of IWWS-influencing factors is possible. This may lead to a better understanding of paper strength development mechanisms at dryness levels below 50%. The applied method has proven to be reliable for the determination of impact factor weighing. This work carried out to what extent changed parameters changes the IWWS in relation to the baselines of beating and dryness. So it was shown that the effect of dryness level as well as the degree of beating are as expected positive and quite big. In relation to this, the effect of hornification is low and the one of conductivity is highly negative. These results give deeper insights into the mechanism of IWWS development and an advanced explanatory model will be presented. The generated knowledge provides the tool for a better understanding of the phenomena of IWWS development and enables the papermaker to optimize the production processes accordingly.