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Cellulose (2021) 28:5775–5791
Fig. 3 Exemplary stress–strain curves measured during dry ( a ) andwet ( b ) tensile testing, from which the maximum force at break (Fmax) and subsequently the tensile indices were calculated
Fig. 4 Dry and wet tensile indices of eucalyptus-sulfate paper samples with a grammage of 80 g m - 2 shown side by side with the amount of copolymer inside the paper samples, as determined by gravimetric analysis for: pure cellulose paper samples not subjected to any treatment (Ref), samples subjected to the procedure for copolymer application, without any copolymer in the solution (RefSwell), and samples where the copolymer was applied out of H 2 O, IPAand BuOH (for more details, see supplementary information)
Studying single-fiber behavior in more depth is of high interest, however, also requires an extensive statistical analysis. Note, at present we did not intend to draw such quantitative information from the tensile- test videos in order to judge which kind of failure mechanism determines the breakage of the wet paper samples most. We instead moved our attention to a
microscopy by other groups as well. (Siqueira 2012) In addition, fiber pull-out was observed as a second typical failure mechanism, shown in Fig. 5b, respec- tively. Both mechanisms, fiber pull-out and fiber delamination driven breakage, have been reported before by others, studying the tensile properties of wet-strengthened paper sheets. (Siqueira 2012)
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