# Evaluation of Recycled Paperboard Properties and Characteristics
## 3 Results and Discussion
### Functional Properties of Recycled Paperboard
\begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline \multirow{2}{*}{**Property**} & \multicolumn{3}{c}{**Uncoated**} & \multicolumn{3}{c}{**Coated**} \\ \cline{2-9}  & **Sample** & **Ladoga** & **HM** & **Umka** & **MCB** & **MCM** & **Neva** \\ \hline Mass per square meter, g/m\({}^{2}\) & 310.9 \(\pm\) 0.2 & 372.8 \(\pm\) 0.2 & 351.6 \(\pm\) 0.2 & 406.2 \(\pm\) 0.2 & 382.1 \(\pm\) 0.1 & 395.3 \(\pm\) 0.2 & 424.0 \(\pm\) 0.1 \\ Thickness, \(\upmu\)m & 555.6 \(\pm\) 8.6 \({}^{*}\) & 498.4 \(\pm\) 6.8 \({}^{*}\) & 483.2 \(\pm\) 6.01 \({}^{*}\) & 513.0 \(\pm\) 4.0 \({}^{*}\) & 531.2 \(\pm\) 5.0 \({}^{d}\) & 554.6 \(\pm\) 5.0 \({}^{*}\) & 532.2 \(\pm\) 28 \({}^{d}\) \\ Bulk density, cm\({}^{3}\)/g & 1.287 & 1.337 & 1.374 & 1.263 & 1.391 & 1.403 & 1.255 \\ Smoothness, s & 5.5 \({}^{*}\) & 4.1 \({}^{*}\) & 4.5 \({}^{*}\) & 38.1 \({}^{*}\) & 76.4 \({}^{d}\) & 53.3 \({}^{*}\) & 38.4 \({}^{*}\) \\ Surface absorption, (water), (Cobb 6), & 572 & 510 & 543 & 204 & 75 & 118 & 48 \\ Surface absorption, & Top & 2 \({}^{*}\) & 2 \({}^{*}\) & 2 \({}^{*}\) & 61 \({}^{*}\) & - & 82 \({}^{*}\) & 165 \({}^{*}\) \\ (ylene), s & Reverse & 1 \({}^{*}\) & 3 \({}^{*}\) & 3 \({}^{*}\) & 9 \({}^{*}\) & - & 35 \({}^{*}\) & 28 \({}^{*}\) \\ Tensile strength, N & MD & 128.4 & 323.6 & 209.5 & 320.2 & 233.8 & 227.4 & 372.0 \\ CD & 124.8 & 115.6 & 111.1 & 95.8 & 102.6 & 135.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Properties of recycled paperboards. of pulp, can enhance the tensile strength by 15-20% [26]. Neva, Ladoga, and Umka paperboards showed higher tensile strength (MD) compared to the other samples. This seems unrelated to their thickness but can be attributed to sizing (Table 2). The laboratory single-plied paperboard sample does not have fiber directions; this is why its tensile strength corresponds to the values of the transverse (CD) direction of the industrial samples. Sizing and coating strongly affect the absorption properties of paperboards, minimizing it. For example, Neva paperboard was the only one with a surface absorptiveness (to water) of 48 g/m\({}^{2}\), with the norm being 20-60 g/m\({}^{2}\) for paperboards without barrier properties. The uncoated paperboards, namely Ladoga and NM, as well as the laboratory Sample, showed unsatisfactory results for both xylene and water absorption. The absorption process depends on the structure of the material; thus, macroporous boards, including uncoated materials from recycled fibers, absorb ink quickly and deeply. As a result, macroporous paperboards are undesirable for illustrative printing, as they may cause loss of color saturation in the image. Microporous paperboards with coating and various fillers are characterized by the \"selective absorption\" mechanism, where the solvent is mainly absorbed into the micropores of the surface by under the force of capillary pressure, while the pigment and binder remain on the surface. This is exactly what is needed to obtain a clear image. In general, the performance of recycled fiber paperboards is lower compared to the standards for virgin fiber ones. Accordingly, these materials may show unsatisfactory results in printing.