Application of nanocelluloses with the assistance of hemicelluloses to improve the properties of recycled paper.

BASTIDA, GABRIELA ADRIANA; MIGUEL A. ZANUTTINI; MARÍA VERÓNICA GALVÁN

Santa Fe

Simposio; Segundo Simposio AUGM-BAYLAT; 2022

AUGM, BAYLAT

Paper recycling implies environmental and economic benefits. Nevertheless, during the successive papermaking process and the life cycle, fibers suffer a physical deterioration that affect its mechanical properties. The objective of this thesis is to use cellulose micro/nanofibrillar (CMNFs) as the strength agent. In a first stage, the obtaining of CMNFs by different methods is considered. For mechanical pre-treatments of fibers, a rotary homogenizer or a PFI mill refiner were considered, and a chemical pre-treatment was performed using oxalic acid at 25 wt% and 50 wt%. Finally, mechanical fibrillation was performed with a pressurized homogenizer (300 bar). CMNFs were fully characterized by different techniques. The best CMNF characteristics were found when the PFI mill refiner was used as mechanical pre-treatment. Besides, the best results of nanofibrillation yield (76.5%), transmittance (72.1%) and surface charges (71.0 µeq/g CMNF) were obtained using 50 wt% oxalic acid. Nevertheless, the highest aspect ratio (length/diameter) determined by Transmission Electron Microscopy (TEM) was found using 25 wt% oxalic acid treatment. CMNFs are difficult to retain in the fiber network and cause a loss of drainage capacity during papermaking. These inconveniences can be improved by adding of a polyelectrolytes complex (PECs) that act as retention agent. In a second stage of this thesis, the use of a natural PEC based on a Xylan (Xyl) solution and a chitosan (Ch) solution with a Xyl/Ch mass ratio of 80/20 was proposed. In this case, CMNFs were obtained using different pressures in the homogenizer (300; 600 and 900 bar). The results show that the maximum retention evaluated in a Britt Dynamic Drainage Jar was obtained when neutral PECCMNF system was added to pulp. Besides, the drainage capacity increased significantly when PEC-CMNF systems were added to pulp. The incorporation of PEC-CMNF systems to the handsheets increased Tensile Index (up to 28%), Mullen Index (up to 40%) and Scott Bond (up to 255%). Finally, the compressive strengths of the handsheets such as SCT and CMT increased up to 30 and 70%, respectively. As future contributions, it is proposed to study the rheological behavior of PEC-CMNFs systems, their interactions and flocculation conditions