Appl. Sci. 2025 , 15 , 875
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The higher strength values observed for the 3.2 wastepaper suggest greater fiber quality or heterogeneity compared to 1.3. This indicates that the effects of retention aids are influenced not only by their concentration but also by the intrinsic properties of the wastepaper. The study highlights the importance of optimizing retention aid dosage to balance its benefits and drawbacks. An excessive or insufficient addition can negatively impact tensile properties. While the 0.8–1.0% range provides a reasonable compromise for strength recovery, further refinements in dosage may be needed to maximize the performance for specific paper grades. The results underline the necessity of tailoring retention agent strategies to the type of wastepaper and desired paper properties, ensuring efficient and sustainable papermaking processes. It should also be noted that higher strength values were observed for the 3.2 wastepa- per, indicating the heterogeneity of the raw material (Tables 2 and 3). The conclusions of the conducted study highlight the need for further innovation in the field of retention aids to improve paper properties without negatively impacting production processes. Future development directions include the creation of retention aids tailored to specific fiber types and wastepaper streams, which will help minimize adverse effects on the mechanical and surface properties of paper. Simultaneously, research is focusing on multifunctional additives, such as nanocellulose and biopolymers, which can simultaneously enhance retention, mechanical strength, and surface quality [42]. A critical element of future solutions is the implementation of advanced process control systems and artificial intelligence, enabling the real-time optimization of wet-end chemistry to ensure consistency and high production quality. Another key direction is the development of biodegradable and non-toxic retention aids, meeting the needs of sustainable development and the growing demand for eco-friendly products. Furthermore, the use of hybrid reten- tion systems, nanotechnology, and advanced modeling tools opens new opportunities to improve the efficiency of production processes and the quality of final products. These innovative approaches will allow the paper industry to meet the increasing environmental, quality, and economic demands. 4. Conclusions Overall, the addition of a retention agent can significantly enhance papermaking efficiency by improving key process parameters such as fiber retention, drainage, sheet formation, and uniformity. Optimized retention systems can lead to achieving higher- quality paper products with reduced raw material losses, minimized environmental impact, and improved operational cost-effectiveness. These benefits are crucial for maintaining competitiveness in an industry where cost and sustainability are critical considerations. However, the conducted analyses demonstrate that while the cationic polyelectrolyte based on acrylamide and a cationic derivative of acrylic acid contributes positively to process efficiency, it can adversely affect certain mechanical and surface properties of recycled paper. Specifically, this study revealed a marked decline in tensile strength and strain at break, with reductions of up to 36% for breaking length and 51% for strain compared to reference samples. Additionally, increased roughness parameters observed in the study suggest that the retention aid adversely affects surface smoothness, an important property for applications requiring high-quality printability or tactile smoothness, such as sanitary papers. The observed trade-offs highlight the importance of optimizing retention aid dosages to balance production efficiency and the functional properties of recycled paper products. While lower dosages improve tensile properties and surface quality, they may compromise retention and drainage efficiency. Conversely, higher dosages enhance retention but can
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