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Effect of PFI and Ultrasonic Wave Pretreatments on the Fiber Morphology and Xanthation Characteristics of Hardwood Dissolving Pulp |
Received:September 21, 2020 |
DOI:10.11980/j.issn.0254-508X.2021.01.002 |
Key Words:dissolving pulp Fock reactivity pore structure crystallinity dissolving process |
Fund Project:国家自然科学基金面上项目(31670588)。 |
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Abstract:In this study, the hardwood dissolving pulp fibers were respectively pretreated by the PFI mill and the ultrasonic wave, and the influences of both pretreatments on the fiber length, width, porosity, surface morphology, cellulose crystallinity and Fock reactivity were investigated. The results showed that PFI pretreatment had little effects on pore volume, specific surface area, cellulose crystallinity and reaction property, while after the 540 W/10 min ultrasonic wave pretreatment, the pore volume of fibers increased from 1.0×10-2 cm3/g to 2.2×10-2 cm3/g, the specific surface area increased from 5.358 m2/g to 9.503 m2/g, the crystallinity degree decreased from 82.57% to 76.38% and the Fock reactivity increased from 38.82% to 49.80%. The dissolution of the pulp fiber in xanthation reagent system was mainly a process of “bubble-shape” swelling-swelling/dissolution-dissolution. As the xanthation reaction went on, the fiber weight-weight length first decreased and then increased, while the fiber weight-weight width continued to increase. The fines content first increased and then decreased, and the cellulose crystallinity continued to decrease and the cellulose partially dissolved. During 3 h xanthation reaction, the fiber weight-weight width increased from 17.6 μm to 34.3 μm and the cellulose crystallinity degree decreased from 76.38% to 57.53%. The fiber weight-weight length decreased from 0.826 mm to 0.547 mm during the period of 0~2 h and then increased to 0.766 mm after 3 h. Fines content increased from 1.2% to 6.2% during the period of 0~2 h, and then decreased to 3.4% after 3 h. |
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