Investigation of the Effect of Combined PFI/Ultrasonic Treatment on the Solubility Performance of Dissolving Pulp in NMMO Solution
A sequential treatment consisting of initial PFI refining,followed by ultrasonic treatment was performed on pre-hydrolyzed sulfate dissolving pulp fibers in this study.The results showed that after the PFI/ultrasonic synergistic treatment,the surface morphology of dissolv-ing pulp fibers was destroyed,most of the primary wall and S1 layer of the secondary wall were removed,and the specific surface area,pore volume,and pore diameter became larger.Softwood dissolving pulp pore diameter increased from 16.76 nm to 21.85 nm from the untreated treatment and from 16.74 nm to 21.61 nm for hardwood dissolving pulp.The changes in fiber morphology characteristics caused a signifi-cant increase in the water retention value and absorbency of dissolving pulp fibers.Softwood and hardwood dissolving pulp water retention values increased by 205.0%and 78.5%,respectively,while the cellulose crystallinity,intrinsic viscosity and molecular weight were re-duced.The PFI/ultrasonic synergistic treatment could effectively improve the solubility of dissolving pulp in NMMO solution.