The influence of nanochitosan addition on the process and quality properties of printing and writing paper made from recycled fibers

Improving the processing and the recycled paper properties is one of permanent concern of papermaking. In this research, the effect of nanochitosan addition on the process and product quality made of writing and printing recycled fiber was investigated. Being nano size and so its capability in access to the space between pulp suspension components and also its probable ability to make electrostatic and hydrogen bonds are the characteristics of nanochitosan. For this purpose, the chitosan nanoparticles were prepared and their size and shape was confirmed with AFM and FE-SEM. Also, the change in FTIR spectrum after conversion of chitosan to nanochitosan was considered and omitting the –NH2 in chitosan and creation of –CONH groups in nanochitosan by polymerization between chitosan and meta acrylic acid were confirmed. In next step, nanochitosan in four levels (0, 0.5, 1, 1.5 and 2% based on oven dry pulp) was used. The results indicated that nanochitosan was successful in increasing the mechanical properties (tensile, burst and tear indices) and process properties (drainage and fines retention) comparing the control treatment (no additive). Moreover, the comparing of nanochitosan and chitosan performance in the same consumption level (1% based on oven dry pulp) showed similar effect on mechanical properties but chitosan had better performance in process properties. Also, both of this polyelectrolyte showed better results on mechanical properties comparing the cationic starch at the same consumption level (1% based on oven dry pulp).