Abstract
Mechanical properties are crucial in assessing the paper quality. Deformation and strength properties of paper are determined by the strength and stiffness of the interfiber and intermolecular hydrogen bonds. The contribution ratio of interfiber and intermolecular hydrogen bonds to the strength of paper can be changed by adjusting the degree of its anisotropy. The article presents the results on a study of the deformation properties of laboratory anisotropic paper samples from kraft bleached softwood pulp with a beating degree of 30 °SR. The samples had basic weight of 90 g/m2 and the degree of stiffness anisotropy TSIMD/CD of 1.75–4.08. They were made by using Techpap SAS automatic dynamic handsheet former (Grenoble, France), with varying forming parameters – diameter of the nozzle, motion speed of the forming wire, and injecting speed of pulp. Deformation properties were determined by tensile test and processing of the stress-strain dependence (σ−ε). The outcomes have shown that, an increase of the fiber orientation degree in paper structure by changing the forming parameters caused a change in the nature of the paper deformation under tension. Increasing the fiber orientation degree in the structure of paper made it possible to increase the strength by 55 %, tensile stiffness by 63 % in the machine direction, while reducing the extensibility by 10 %. In the cross direction, it was possible to decrease tensile stiffness by 33 %, strength by 55 %, and increase the extensibility by 5 %. Anisotropy of tensile strength was 1.73–6.00. The greatest effect was obtained for the elasticity modulus in the pre-failure zone E2 (2.8–38.6). It means that, fiber orientation had a key importance when large deformations in the samples took place. The established quantitative regularities allowed optimizing the values of the deformation and strength properties of paper, and their ratio in the machine direction and cross direction due to the variation of the forming parameters. For citation: Rech D., Potasheva A.N., Kazakov Ya.V. Regulating the Deformation Properties of Paper by Varying the Degree of Its Anisotropy. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 5, pp. 174–184. DOI: 10.37482/0536-1036-2021-5-174-184
Highlights
Strength and deformation characteristics are key markers to evaluate the quality of pulp and paper products
The aim of this work is to establish quantitative regularities that connect the parameters of the paper forming on the dynamic sheet former and the degree of anisotropy of laboratory paper samples, which make it possible to control the values of their deformation and strength properties, including optimizing the ratio of these values in the machine direction (MD) and cross direction (CD)
When optimizing the forming mode, it is necessary to take into account the simultaneous and multidirectional change of the paper properties in the MD and CD
Summary
Strength and deformation characteristics are key markers to evaluate the quality of pulp and paper products. The modern scientific approach and the latest engineering technologies make it possible to model the structure of pulp and paper materials, to test and analyze their properties at a stage of laboratory research. They give a chance to obtain anisotropic laboratory samples with characteristics like or similar to those of final products of papermaking and cardboard machines (PM and CM, respectively). The aim of this work is to establish quantitative regularities that connect the parameters of the paper forming on the dynamic sheet former and the degree of anisotropy of laboratory paper samples, which make it possible to control the values of their deformation and strength properties, including optimizing the ratio of these values in the machine direction (MD) and cross direction (CD)
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