The effect of cationic polyacrylamide on properties of old corrugated containers (OCC) recycled pulp reinforced with paulownia fortune’s nano lignocellulosic fibers

Abstract
Background and objectives: One of the disadvantages of recycled fibers is the significant loss of mechanical strength of the paper due to the decrease in the bond between the fibers. So far, many types of research have reported the application of cellulose nanofibers in the production processes of paper products. The results of previous research show that the use of cellulose nanofibers strengthens paper products. However, the amount of this reinforcement is different according to the type of cellulose nanofibers used. Nano lignocellulosic fibers of paulownia fortune (Nano wood) consist of nanoscale fibers with the same chemical composition as wood, which is produced mechanically without the use of chemicals from lignocellulosic biomass at ambient temperature. This material is a brown gel, which has a completely environmentally friendly production process. The objective of this study was to investigate the effect of adding Paulownia nano-wood on the improvement of pulp from old corrugated containers (OCC).
Materials and methods: The pulp was prepared from OCC collected and after refining and obtaining a flow rate of 380 ± 20 ml, different amounts of paulownias nano-wood (1, 2, and 3%) and cationic polyacrylamide (0.1, 0.2, and 0.3%) was added to it. Finally, standard hand sheet papers were made from these treatments, and their physical and mechanical properties were measured according to the TAPPI standards.
Results: Using nano wood and cationic polyacrylamide simultaneously causes a significant increase in resistance properties. The results show that the simultaneous addition of cationic polyacrylamide-nano wood to the pulp obtained from old corrugated containers increases the resistance to air permeability and density due to the improvement of the content of the bond and also the reduction of the porosity of the paper structure. According to the results, the highest strength in the nano lignocellulosic fibers -cationic polyacrylamide system among different treatments was observed in samples containing 1 % of nano wood and 0.3 % of cationic polyacrylamide. The results of evaluating the physical properties of the papers showed that the density and air resistance of paper (Gurley method) increases with the addition of lignocellulosic nanofibers - cationic polyacrylamide in the paper. The results show that the simultaneous addition of lignocellulosic nanofibers - cationic polyacrylamide to the pulp obtained from Old corrugated container (OCC) increases the air resistance of paper and density due to the improvement of bonds and also the reduction of the porosity of the paper structure.
Conclusion: Due to its positive charge, cationic polyacrylamide improves the bonding between fibers and restores lost bonds, and also prevents the wastage of fine nano wood particles and thus improves the properties of the paper. The statistical analysis showed that 95 % confidence in accuracy between treatments in the mechanical strengths (burst, RCT, and tensile strengths) is different. Using optimum levels of nano lignocellulosic fibers improves these strengths. According to the results, the best’s amount of strength among different treatments in the lignocellulosic nanofibers-cationic polyacrylamide system is observed in samples containing 1% lignocellulosic nanofibers and 0.3% cationic polyacrylamide.