Microwave-assisted non-thermal hemp degumming

The microwave-assisted non-thermal degumming of hemp fibre has been studied and then compared with the water bath heating under different time and temperature conditions. The results show that the residual gum content of the lean hemp using microwave-assisted heating method is lower than that obtained using water bath heating. The residual gum content gap between the two degumming processes increases first and then decreases as the heating time and temperature are increased. This proves the existence of non-thermal effects in microwave heating process besides the thermal effects in water bath heating. In addition, the structures of the lean hemp fibres obtained from these two methods are also studied by scanning electron microscopy and fourier transform infrared spectroscopy.

The Ninth Visual Object Tracking VOT2021 Challenge Results

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Structure, Composition, and Thermal Properties of Cellulose Fibers from Pueraria lobata Treated with a Combination of Steam Explosion and Laccase Mediator System

Cellulosic fibers from the bast of Pueraria lobata (P. lobata) vine were separated using a “green” and efficient method that combined steam explosion (SE) and a laccase mediator system (LMS). The chemical components, structure, and thermal alterations in the fibers were evaluated. The SE performed at 180 °C for 10 min did not change the chemical composition of P. lobata; however, SE did alter the fiber structure and rendered its surface more accessible to the laccase enzyme. Treated and untreated samples were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), thermogravimetric analysis (TGA), and chemical methods. The cellulose content of the processed fibers was approximately 68.2%, and the lignin content was 11.8%, which was much lower than the 22.98% lignin content of the raw material. The cellulose fibers exhibited higher cellulose crystallinity and thermal stability compared with the untreated samples. This combined treatment approach may be useful for the isolation of cellulose fibers for composites, textiles, and other industrial applications

Comparison of Different Methods to Produce Pineapple Leaf Fibers with Steam Explosion

Pineapple leaf fibers are abundant but not completely utilized because of the production methods. In this research, the steam explosion process combined with traditional methods including steam explosion after retting, retting after steam explosion, steam explosion after scraping, and hand-scraping only were employed. And they were characterized by X-ray diffraction, scanning electron microscopy, gel permeation chromatography, Fourier-transform infrared, chemical composition, and mechanical test. Results showed that the fibers obtained by steam explosion after scraping method contain the highest percentage of cellulose, the lowest percentage of hemicellulose and lignin, and also the best crystallinity and breaking tenacity with a reasonable degree of polymerization

The Dimensional Distribution of Kenaf and Apocynum Fibers

In this research, single fiber cell separation method was studied and optimized. More than 200 fiber cell dimensional sizes of kenaf and apocynum were analyzed. Furthermore, the diameter changes of kenaf fiber cell before and after different degumming treatments were also explored. Results showed that the average length and diameter of kenaf fiber are 2.16 mm and 10.56 μm, while the average length and diameter of apocynum fiber are 9.04 mm and 7.41 μm. It was also found that the average diameter of kenaf and apocynum fibers decreased with the degumming process, and the diameter distribution became more even

The effect of cooling temperature on the skin-core crystalline structure of β-nucleated polypropylene using finite element analysis

Heat transfer during cooling process influences the formation of crystal modification of polypropylene (PP) with nucleating agent (β-nucleated polypropylene). In this study, finite element method (FEM) was applied to simulate the cooling process in PP. Additionally, the skin-core crystalline structure of β-nucleated polypropylene cooled at different temperatures was studied by a wide angle of X-ray diffraction (WAXD). The non-thermal crystallization behaviour of β-nucleated polypropylene was further studied based on the results of FEM. The results indicated that, based on temperature field, FEM was capable of calculating the cooling rate in the skin and core layers of samples. When the cooling temperature increased from 20 °C to 100 °C, the cooling rate decreased from 702.64 °C/min to 79.04 °C/min, and from 119.49 °C/min to 40.00 °C/min in the skin layer and core layer, respectively. The difference of cooling rates from the skin layer to the core layer decreases with the increasing of cooling temperature. Correspondingly, the skin-core crystalline structure is proved to react to the gradient of cooling rate. The non-thermal crystallization also implies that the relative content of β-phase increases with the increasing of temperature, which may attribute to the longer residence time in the temperature range from 105 °C to 140 °C. Keywords: Polypropylene, Finite element method, Skin-core crystalline structure, Non-thermal crystallization behaviour, Cooling rat

Steam Explosion and Alkali-Oxygen Combined Effect for Degumming of Kenaf Fiber

Kenaf is an economically viable and ecologically friendly cellulose source. It can be used in the textile, paper, and bio-energy industries, but it has not been effectively developed and utilized because of degumming problems. To effectively take advantage of kenaf resources, to satisfy the growing demand for natural fiber, and to provide support for other fiber material degumming, steam explosion (STEX) pretreatment followed by alkali-oxygen treatment was studied. The effect of pressure on the properties of kenaf during the STEX treatment was studied, and the optimal degumming process for kenaf was selected. Results showed that STEX pretreatment removed pectin and part of the hemicellulose. Carbohydrates (cellulose and hemicellulose) could be degraded via high pressure treatment. The residual gum content and the fineness of the kenaf fiber after the alkali-oxygen treatment were good enough for textile production. High pressure was found not to be a key factor influencing the degumming process. Low pressure STEX (0.5 MPa) and alkali-oxygen treatment was judged to be an efficient method for degumming kenaf fibers

The Influence of Fiber Length Distribution on Yarn Properties Based on Fiber Random Arrangement in the Yarn

This study discussed the influence of fiber length distribution on yarn qualities (yarn irregularity and strength) based on simulation on fiber random arrangement. Yarn limit irregularity is expressed as the variation of total fiber length that could be found in each yarn subsection. Yarn strength is expressed as the total contributions that breaking and slipping fibers make to yarn strength. Fiber slippage or breakage depends on critical slipping length. Ramie yarns with different stretch-broken fiber lengths were introduced to verify the calculation. Results show that yarn limit irregularity is only dependent on average fiber length and is irrelevant with the distribution type of fiber length. Yarn limit irregularity rises slowly with the increase of average fiber length. Nevertheless, fiber length distribution has significant effect on yarn strength. When average fiber length and its variation are identical, the left deviated distribution may lead to a lower yarn strength, while the right deviated distribution may obtain a higher yarn strength. Therefore, understanding the influence of fiber length distribution on yarn properties will be helpful for selection of fiber length to produce high-quality yarns

A theoretical analysis of local thermal equilibrium in fibrous materials

The internal heat exchange between each phase and the Local Thermal Equilibrium (LTE) scenarios in multi-phase fibrous materials are considered in this paper. Based on the two-phase heat transfer model, a criterion is proposed to evaluate the LTE condition, using derived characteristic parameters. Furthermore, the LTE situations in isothermal/adiabatic boundary cases with two different heat sources (constant heat flux and constant temperature) are assessed as special transient cases to test the proposed criterion system, and the influence of such different cases on their LTE status are elucidated. In addition, it is demonstrated that even the convective boundary problems can be generally estimated using this approach. Finally, effects on LTE of the material properties (thermal conductivity, volumetric heat capacity of each phase, sample porosity and pore hydraulic radius) are investigated, illustrated and discussed in our study

The influence of complexes' configuration, ligand's properties and trans-effect on the acid-catalyzed reaction mechanisms of trans-Ru(py) 4(NO2)2, trans-Ru(bpy)2(NO 2)2 and cis-Ru(bpy)2(NO2) 2

The results of the acid-catalyzed reaction under similar conditions of three dinitro complexes, trans-Ru (py)(NO), trans-Ru(bpy)(NO), and cis-Ru(bpy) (NO) (py = Pyridine, bpy = 2,2′-bipyridine) were analyzed and compared. It was found that the results depend obviously on the configuration of the complexes, structures of the ligand, and the trans-effect of the opposite ligand. The trans-effect of the ligand influences or changes the mechanism and the pathway of the acid-catalyzed reaction of the NO ligand in a Ruthenium (II) complex. If the ligand with strong trans-effect is opposite to the reactive ligand (NO), the substitution reaction of NO ligand will take place through disassociation mechanism, however, if the opposite ligand is a weak trans-effect one, such as OH, bpy, etc., the decomposition of NO ligand will occur. Whether the complexes configuration is trans or cis, the bound structure of bpy will influence the stability of the five-coordinated transition state, and also the pathway of the reaction