Cross-linked polyvinyl alcohol modified by aziridine cross-linker for effective paper sizing

Cross-linked polyvinyl alcohol (AZ-CIPVA) for effective paper sizing was prepared by using N-(isobutoxymethyl)acrylamide (IBMA) and aziridine cross-linker (AZ) as modifiers. The structure and the performances of the AZ-CIPVA with different dosage of AZ were characterized. The enhancing mechanism of paper sized by AZ-CIPVA was clarified. The results show that cross-linking structure is formed by the reaction between AZ and carboxyl groups in CIPVA molecules. With the increase of AZ content, the gel content, cross-linking density and thermal stability of the AZ-CIPVA film are increased. When the AZ dosage is 3.5%, both tensile strength and modulus of AZ-CIPVA film reach maximum, and the value are 68.34 MPa and 1037.02 MPa, respectively. The water absorption of the film reaches minimum and the folding endurance of the sizing paper reaches maximum when the content of AZ is 2.8%. When applied to the surface of the paper, the maximum dry and wet tensile indexes of the paper are increased by 223.77% and 432.56%, respectively. Roughness of the sizing paper increases slightly and the surface becomes uneven. The micro-structure shows that larger pores between the paper fibers are filled and cross-linked after sizing, which is beneficial to improve the mechanical strength of paper.