Cellulose (2016) 23:2249–2272 DOI 10.1007/s10570-016-0961-7
REVIEW PAPER
Initial wet web strength of paper
Ju¨rgen Belle . Ju¨rgen Odermatt
Received: 13 August 2015 / Accepted: 10 May 2016 / Published online: 17 May 2016 The Author(s) 2016. This article is published with open access at Springerlink.com
Abstract Despite much research into and develop- ment within the complex area of the initial wet web strength of paper, no complete model has yet been developed to describe this property. This type of paper strength is the most important property to ensure an effective paper machine run. Furthermore, the process of strength development in the sheet forming and pressing portion of the process is the basis of the final paper strength. Recent investigations have focused on the surface interactions of fibers on the molecular level. There have also been several innovative findings about fiber swelling and the impact of swelling on the mechanical characteristics of fibers in wet conditions. Overall, progress obtained using new methodologies enables a deeper understanding of the mechanism of strength development. This review discusses these important areas by examining the literature and the authors’ own work to obtain a better understanding of the strength development in wet paper webs. This paper highlights that the fiber morphology and the dryness of the wet web have the greatest impact on the strength of the wet web. As fiber sources and J. Belle ( & ) Department of Paper Technology, Munich University of Applied Sciences, 80335 Munich, Germany e-mail: belle@hm.edu J. Odermatt Fakulta¨t MIN Fachbereich Biologie Zentrum Holzwirtschaft, University Hamburg, Hamburg, Germany
machinery are fixed, the fiber water gel is one of the easiest factors to adjust via the process water quality and the use of chemical additives. Capillary force Dryness Fiber water gel Frictional connection Measurement technique Van der Waals force Keywords
Introduction
There is a clear trend in the paper industry towards lower grammages and higher machine speeds to increase productivity while conserving resources and energy. Especially in packaging papers, there is a trend to decrease base weight from 110 to 130 g/m 2 down to 70 to 90 g/m 2 with machine speed up to 1900 m/min (Guldenberg and Schwarz 2004; Mu¨ller 2010). Most papers are manufactured on machinery with an open draw downstream of the forming and/or pressing section (Berger and Schramm 2011; Erhard and Kretschmer 2007; Schwarz and Bechtel 2003). Thus, the initial wet web strength (IWWS) is the utmost important factor for setting the paper in the first open draw, where the paper web is transferred without external support in the paper machine. As a result, the IWWS is the central parameter that controls the number of breaks at this point of the production process (Clark 1978c; Edvardsson and Uesaka 2009; Guldenberg and Schwarz 2004; Lindqvist et al. 2012;
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