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The purpose of this paper is to study the effect of treatment using hydrophilic and hydrophobic polymers on mechanical properties and/or water absorption of paper sheets.

Paper sheets produced from paper grade wood pulp were dipped in polyacrylamide (PAA), polymethylmethacrylate (PMM) and polyvinyl alcohol (PVA) polymer solutions, respectively. The effects of using different polymer solutions (PAA, PMM and PVA), as well as the effects of dipping time (1, 5 and 10 min) and concentration of polymer (0.5, 1, 2 and 3 per cent), on the mechanical properties as well as water absorption of paper sheets were investigated.

It was found that the treatment of paper sheets with different polymer solutions improved mechanical properties as well as water absorption of paper sheets when the polymer concentration was below 1 per cent and the dipping time did not exceed 5 min.

Paper sheets resulting from treatment using hydrophilic polymers can be used as printing papers as the printability improves because water absorption improves, while paper sheets resulting from using hydrophobic polymers can be used for packaging because water adsorption is less and breaking length improved.

Improving some mechanical properties and/or water absorption of paper sheets. The improvement of dipped sheets increased by increasing dipping time till 5 min and by increasing polymer concentration till 1 per cent. Utilisation of PAA led to best results especially when it was hydrolysed.

In recent times, ternary hybrid nanofluid has garnered attention from scientist and researchers due to its improved thermal efficiency. This study aims to delve into the examination of ternary hybrid nanofluid (Al₂O₃–Cu–TiO₂/water), particularly concerning axisymmetric flow over a nonlinearly permeable stretching/shrinking disk. In addition, the investigation of convective boundary conditions and thermal radiation effects is also considered within the context of the described flow problem.

Mathematical formulations representing this problem are reduced into a set of ordinary differential equations (ODEs) using similarity transformation. The MATLAB boundary value problem solver is then used to solve the obtained set of ODEs. The impact of considered physical parameters such as suction parameter, radiation parameter, nonlinear parameter, nanoparticle volumetric concentration and Biot number on the flow profiles as well as the physical quantities is illustrated in graphical form.

The findings revealed the thermal flux for the nonlinearly shrinking disk is approximately 1.33%, significantly higher when compared to the linearly shrinking disk. Moreover, the existence of dual solutions attributed to the nonlinear stretching/shrinking disk is unveiled, with the first solution being identified as the stable and reliable solution through temporal stability analysis.

Understanding ternary hybrid nanofluid behavior and flow has applications in engineering, energy systems and materials research. This study may help develop and optimize nanofluid systems like heat exchangers and cooling systems.

The study of flow dynamics across nonlinear stretching/shrinking disk gains less attention compared to linear stretching/shrinking geometries. Many natural and industrial processes involve nonlinear changes in boundary shapes or sizes. Understanding flow dynamics over nonlinear shrinking/stretching disks is therefore essential for applications in various fields such as materials processing, biomedical engineering and environmental sciences. Hence, this study highlights the axisymmetric flow over a nonlinear stretching/shrinking disk using ternary hybrid nanofluid composed of alumina (Al₂O₃), copper (Cu) and titania (TiO₂). Besides, this study tackles a complex problem involving multiple factors such as suction, radiation and convective boundary conditions. Analyzing such complex systems can provide valuable insights into real-world phenomena where multiple factors interact.