Cellulose (2016) 23:2249–2272
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Fig. 1 Factors influencing the breaking load of paper according to Brecht and Erfurt (1959a, b)
within a sheet of paper at different dryness levels, such as flexible and smooth fibers that enable contact points between fibers (Brecht and Erfurt 1959a, b; Lyne and Gallay 1954a, b). After many years, various authors have begun working on these correlations again, addressing the factors affecting these forces such as capillary forces, van der Waals forces, and entangle- ment that leads to frictional connections (Hubbe 2006; Tejado and van de Ven 2010; Wa˚gberg 2010; Wa˚gberg and Annergren 1997). It is well known that the dependence of strength on the dryness level is not linear, but over a certain range exponential. In addition, different forces of different magnitudes such as capillary and frictional forces do overlap at specific dryness levels, resulting in a force responsible for the paper strength in the first open draw. Given this background, it is necessary to evaluate the measured strength values in relation to their
Fig. 2 Explanatory levels
level, and the IWWS is not an exception. Even in early papers from the last century, several authors noted that certain conditions are responsible for the strength
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