In this study, we found an environmentally friendly system in the degumming of hemp fiber without using a strong acid and alkali. The chemo-enzymatic modification and degumming of hemp fiber used an acetic acid–sodium acetate buffer solution containing laccase, hemicellulase and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) under a mild condition (pH = 5, T = 50℃). Through comparing and analyzing the physical and chemical properties of fiber products under different treatments, we found the method involving treatment with TEMPO/laccase/hemicellulase not only greatly removed most of the gum attached on the surface of the raw hemp fiber, but also introduced surface-active aldehyde and carboxyl groups into the fiber. The performances of the hemp fibers with different treatments were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction. We also found the product was finer, with a lower content of non-cellulosic components and it had better water uptake properties (moisture sorption and water retention value), which has potential application values in textile industries.
In this study, different dosages of NaClO were used in the 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-laccase degumming system to remove non-cellulosic materials, and their effects on the structure of hemp fibers were analyzed and discussed. A scanning electron microscope was used to depict the surface morphology of fibers after oxidative degumming under various dosages of NaClO in the TEMPO-laccase degumming system. Chemical composition analysis was used to determine the content changes of the different components. Meanwhile, the content of functional groups was also discussed. Fourier transfer infrared spectroscopy, nuclear magnetic resonance spectroscopy, and X-ray diffraction were employed to evaluate the microstructural changes of degummed hemp fibers obtained from the degumming processes with different dosages of NaClO. The results showed that after the TEMPO-laccase system degumming process with a NaClO dosage of 16%, the cleanest and smoothest surface of degummed fibers could be observed and the non-cellulosic materials were significantly removed without any crystalline transformation or damage in the cellulose. This research could shed light on determining favorable operation parameters for hemp oxidation degumming and increasing the degumming efficiency, as well as in the oxidation control and quality assurance of hemp fibers for textile downstream end uses.
Hemp fiber's origin has a large impact on the physical properties of degummed fibers. In this research, the effect of hemp fiber origin on the treated fibers was studied mainly by evaluation of chemical composition and microstructure, as well as by the evaluation of the degummed fiber's properties under a biochemical process. The samples were chosen from the stem with two different growth periods (an early and a late harvest time) and three different sections along the hemp stem (top, middle, and bottom). The results showed a vast variety of chemical compositions and microstructures for raw hemp fibers in different growth periods. The results of the chemical composition analysis indicated that the cellulose content in raw fibers ranged from 41.9±2.3% to 44.8±0.8% and that the lignin content ranged between 12.0±1.5% and 16.5±0.9%. Both the Fourier transform infrared (FT-IR) and X-ray diffraction (XRD) results demonstrated the close relation of the raw fiber's character to the growth period and sampling section. The physical properties of degummed fibers with different origins were also tested, and large variations in length and linear density were found, which ranged from 42 mm to 67 mm for length and from 11.36±0.37 dtex to 21.55±0.54 dtex for linear density.
TEMPO-media oxidation and laccase have been successfully used in fiber degumming, but the combination of the two methods in the hemp degumming process has not yet been reported. In this paper, an alternative and efficient way for the pretreatment of hemp degumming was proposed as a combination of TEMPO-media oxidation with laccase and was a TEMPO-laccase system. A chemical composition analysis, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) were applied to systematically analyze and compare the degumming efficiency between the TEMPO-laccase system and other pretreatments. The results showed that after the TEMPO-laccase system degumming process, a clean and smooth surface of the degummed fibers could be observed and the non-cellulosic materials were greatly removed without any crystalline transformation. The hemp fibers after the TEMPO-laccase system degumming process had the most desirable linear density of 6.64 dtex and a tenacity value of 3.41 cN/dtex. This new pretreatment had a considerable effect on hemp degumming, which holds promise for use of high-value textiles.
Hemp fiber, as a kind of renewable textile fiber, has evoked much interest due to its excellent properties in various fields. It has been investigated in just one step to finish the process of chemo-enzymatic degumming and modification of hemp fiber, which is done in acetic acidsodium acetate buffer solution containing laccase (6.0 g), hemicellulase (0.3 g) and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (0.3 g) under a mild condition (pH 5, 50C). The degumming effects of different batches of raw hemp fibers were also discussed. We found that the residual rate, fineness, length and tensile strength of degummed fiber were 15–27%, 9.00–24.00 dtex, 14.00–19.00 cm and 3.8–5.1 cN/dtex, respectively. Meanwhile, some of the oxidized functional groups were introduced into degummed fiber, which improved the moisture absorption and water retention value of the hemp fiber. The hemp fiber treated by this process could be further improved and then applied in the textile industry.
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