Oxidized cellulose can be produced from the oxidation reaction of hydrogen peroxide in the degumming process of ramie fibers. In this work, the contents of aldehyde and carboxylate groups in ramie cellulose which occurred during the degumming process were quantitatively determined by the electric conductivity titration method. The morphological changes and chemical components of oxidized cellulose were characterized using SEM, XRD, and FT-IR. Additionally, the relationship between the contents of the oxidized groups and the mechanical properties of the degummed fibers were discussed and analyzed. Results showed that the presence of aldehyde and carboxylate groups in the cellulose contributed significantly to the loss of tenacity, breaking elongation, softness, and degree of polymerization of degummed fibers. When the aldehyde content varied from 20 to 35  µmol/g and the carboxylate content varied from 140 to 180 µmol/g, respectively, raw fibers could achieve desired and reasonable degumming results. This study could offer useful information in obtaining optimal operation parameters for ramie oxidation degumming and better control of fiber quality. The degree of oxidation and content of oxidized cellulose could be used as effective indicating factors to demonstrate oxidation degumming efficiency and fiber properties.

In this paper, anthraquinone was used to improve the properties of ramie fiber in oxidation degumming. The chemical components, structure properties, tensile properties of degummed fiber and the character of oxidation degumming solution were tested and analyzed. With the optimal dosage of anthraquinone (2% (o.w.f.)), the content of hemicellulose, the yield of degumming process, polymerization degree and the work of rupture of the degummed fiber were improved by 17.3%, 7%, 2% and 41%, respectively. The oxidation reduction potential (ORP) value of the degumming solution was also tested, with the addition of anthraquinone, and the ORP value decreased by 250 mV, which is of benefit for the properties of fiber.

Sodium hydroxide is commonly used as the main alkali source in the oxidation degumming of ramie in the current studies for natural fiber extraction. However, due to the strong alkalinity of sodium hydroxide, the oxidation reaction speed of hydrogen peroxide is difficult to control and thus results in great damage to the treated fibers. In this paper, magnesium hydroxide was selected as an effective sustained-release alkali source to improve the tensile properties of degummed fibers and reduce the chemical oxygen demand (COD) values of degumming wastewater. This novel reagent can adjust and buffer pH values in the degumming solution. The chemical components and structure properties of degummed fibers were characterized by Fourier transform infrared spectroscopy and X-ray diffraction, respectively, and the as-developed oxidation degumming solution performance was monitored by an oxidation–reduction potentiometer. The results showed that the optimal substitution rate of magnesium hydroxide was 20% during the oxidation process. Compared with the degummed fibers without magnesium hydroxide, the tenacity, work of rupture and degumming yield of treated fibers increased by 39.82%, 46.15% and 5%, respectively. Moreover, the COD values of wastewater decreased by 20% at the same time.

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