Appl. Sci. 2025 , 15 , 875
6of 12
While retention agents are generally known to influence fine fiber and filler reten- tion, their negligible impact on air permeability in this specific study underscores the importance of other factors. These include the composition of the recycled pulp or the manufacturing process parameters, which may have a more pronounced effect on poros- ity and related properties. Understanding and optimizing these factors is critical when tailoring air permeability to align with target properties like absorbency, printability, or barrier performance. In summary, the structural properties of the studied papers highlight the interplay be- tween air permeability, porosity, and other functional attributes. By carefully adjusting the type and dosage of retention agents, it is possible to tailor paper properties to meet specific performance criteria for diverse applications. This approach underscores the importance of a holistic understanding of material interactions in recycled paper production. Another tested parameter, i.e., roughness, is closely related to porosity. The tests performed indicate that the roughness of reference papers (406 μ m for 1.3 wastepaper and 553 μ m for 3.2 wastepaper) is significantly lower compared to the samples with the highest addition of retention agent, where the maximum roughness reached 1281 μ mand 1084 μ m for pulps 1.3 and 3.2, respectively. This significant increase highlights the impact of retention agent dosage on paper structure. The data (Figure 1) show a general trend: increasing the addition of the retention agent typically leads to higher roughness, although certain deviations are observed. For 1.3 wastepaper, roughness increases steadily from 525 μ m at a 0.1% addition to a peak of 1281 μ m at 0.5% before declining slightly at higher dosages. Conversely, for 3.2 wastepaper, roughness increases more linearly, reaching its maximum at 1.0% retention agent addition (1084 μ m).
Figure1. Roughness of tested wastepaper as a function of retention agent addition.
This behavior may be attributed to the interaction between the retention agent and fiber structure. According to research, rougher paper surfaces can result from uneven distribution of fines and fillers caused by excessive retention agent usage. Initially, the retention agent facilitates the formation of a more porous network by promoting better flocculation, which increases roughness. However, beyond a certain dosage, excessive
Made with FlippingBook interactive PDF creator