Improving the Mechanical Strength of Paper Sheets Made from Phosphorylated Fibers Through the Use of Forming Agents

The fabrication of paper or cardboards sheets with phosphorylated pulp fibers has proven to be a difficult task using traditional papermaking techniques. This problem is mainly attributed to the very high anionic charge of phosphorylated fibers. In the present work, we propose the use of cationic polymers as a neutralizing agent to attenuate the detrimental effect of the very high anionic charge of phosphorylated fibers and to promote the formation of microflocs that can be agglomerated into a uniform sheet with sufficient strength. The results obtained show that using positively charged retention agents significantly improves the sheet formation. The Kaptra formation index (KFI) was reduced from 133 to 17, which is a very good value when compared to unmodified kraft pulp fibers, which have a formation index of 35. The addition of cationic polymeric additives during the preparation of phosphorylated fiber sheets resulted in an improvement of mechanical properties over unmodified kraft pulp fibers, especially for tensile energy absorption and elongation. This study demonstrates that the use of cationic retention agents reduces the impact of the charge of the phosphorylated fibers on the overall sheet quality.