Advanced Materials Research Vols. 175-176

Abstract: The meta-aramid nanofiber webs were successfully prepared by electrospinning with the solvent system LiCl/DMAc in this paper. The uniform nanofibers were obtained when the concentration of the spinning solution was larger than 9wt%, and the microstructure and physical properties of the nanofiber webs were examined. To date, the webs had a better mechanical property when the concentration of the spinning solution was 11wt%. Whereafter, we mainly investigated the effects of heating temperature on the properties of the mate-aramid nanofiber webs. After heat treatment, the structure and property change of the nanofiber webs were analyzed by means of SEM, XRD, TGA, and the tensile strength was measured by Kawabata Evaluation System (KES). The results indicated that there was no significant weight loss and retained a favourable mechanical property when the heating temperature was below 200°C, however, the properties of nanofiber webs would decrease if the heating temperature were increased or the heating time was more prolonged.

Abstract: The decorative composites composed of silk fabric/PE film were characterized by easy cleanness, corrosion-resistance, anti-oxidation and other virtues. In this paper, silk fabric/PE film decorative composites were prepared by hot pressing method. The optimum thickness of the silk fabrics and PE film was fixed by color difference analysis. The effects of hot-pressing temperature, hot-pressing pressure, and hot-pressing time on mechanical properties were studied through single factor analysis method at a certain thickness. The results showed that under the hot pressing conditions (temperature145 °C, pressure 3 MPa, time 4 min and thickness 0.3 mm), silk fabric/PE film decorative composites with ideal tensile strength, bursting strength, tearing strength and color vividness could be obtained. This paper provided an effective approach to the comprehensive utilization of silk fabrics for preparation of decorative composites.

Abstract: Differences in secondary structure among Bombyx mori (B. mori) silk and two wild silks of Antheraea yamamai (A. yamamai) and Antheraea pernyi (A. pernyi) were investigated by CP/MAS 13C NMR Spectroscopy. The β-sheet structure was primary in three silk, and B. mori silk had the highest β-sheet structure. Although amino acid compositions are very similar for two wild silk, their secondary structures had significant difference. A. yamamai silk contained more α-helix structure, whereas more β-turn and random coil structures formed in A. pernyi silk. B. mori silk was mainly composed of anti-parallel β-sheet structure, however, the parallel β-sheet structure was advantage in the two wild silks, and A. yamamai silk contained more anti-parallel β-sheet conformation than A. pernyi silk.

Abstract: We studied the effect of gap size on molecular orientation and crystalline structure of theuniaxially well-aligned nylon 6 nanofibers produced in the gap of the negatively charged metal plates. As evidenced by polarized FT-IR spectroscopy, relative intensity in several absorbance bands, including the N-H stretching, amide I, II, and III vibrations were found to be different in the parallel and perpendicular polarized FT-IR spectra. Moreover, X-ray analysis indicated that the metastable γ-form was predominant in the as-spun nylon 6 nanofiber, and was transformed into the thermodynamically stable α-form by increasing the cap size. These results suggested that the polymer chains were oriented perpendicular to the fiber direction. Molecular orientation to the fiber axis was enhanced as increasing the gap size.

Abstract: Recently, we have reported that syndiotactic polypropylene (sPP) fibrous membrane could be successfully prepared from a multi component solvent system via electrospinning at room temperature. The base solvent of multi component solvent system was cyclohexane. As demonstrated SEM images, the formation of rough surface morphologies and the microholes on electrospun sPP fibers were observed. In this study, we successfully prepared sPP nanofiber webs from a different base solvent was decalin. SEM study demonstrated that the sPP nanofibers prepared from decalin based solvent had smoother surface morphology unlike cyclohexane based solvent, suggesting that the surface morphology of electrospun sPP nanofibers depended on the boiling point of each solvent used. Moreover, to investigate the crystal and molecular structures of electrospun sPP fibers from a different solvent system (i.e., decalin and cyclohexane based solvents), WAXD and FT-IR analysis were carried out. The results showed that the different solvent systems caused the different surface morphologies but the crystal and molecular structure of the electrospun sPP fibers didn’t change.

Abstract: We report the electrospun poly(L-lactide) (PLA) nanofibers incorporating polyhedral oligosilsesquioxane (POSS)-modified multiwalled carbon nanotubes (MWNTs). FT-IR, transmission electron microscopy (TEM) and Raman analysis confirmed the existence of POSS macromers bonded to the MWNTs as an extra phase. The thermal and microstructure properties of the PLA hybrid nanofibers with POSS-modified MWNTs were investigated by thermogravimetric analysis (TGA) and Wide-angle X-ray diffraction (WAXD).

Abstract: In this study, we attempted to produce experimentally a posture correction wear for prevention of 'low back pain'. Then physiological response (i.e. muscular activity and physical energy consumption) and psychological response (i.e.sensory evaluation) were measured when subjects walked on the treadmill wearing the posture correction wear or a commercial lumbar supporter. Fromthe result, the posture correction wear was evaluated ’easy to walk’ in psychological evaluation. It was also found that the posture correction wear gave low constraint on walking, because the muscular activity related to a behavior of coxa was lower when subjects wore the posture correction wear.

Abstract: Electrospinning is a scientifically attractive spinning technique, since it can produce fibers with the diameters ranging from the sub-micron to nano dimensional scale. The fiber diameters and their standard deviation primarily depend on the polymer solution properties and electrospinning process variables. Silk sericin powder was obtained from the raw silk fiber of Bombyx mori silkworm. The solution was prepared by dissolving silk sericin powder in water at 85 °C for 30 minutes. In the electrospinning process, voltage 20 kV was applied and the inner diameter of the syringe needle was 0.3 mm. The distance from the syringe tip to the target was 15 cm. The sericin nanofibers with smooth surfaces can not be produced at 40 wt%. However, fine nanofibers were produced at the concentrations of 50 wt% and 60 wt%. It was suggested that the average diameters of the nanofibers increased with increasing solution concentration and the optimum concentration was 50 wt% for best nanofibers. Then solution 50 wt% was electrospun with different voltages from 13 kV to 25 kV, the working distance is 10 cm, the as-spun silk nanofibers were produced and exhibited fine nanofibers with smooth surfaces. The average diameters and diameter distributions of the nanofibers decreased with increasing voltage.

Abstract: Genetic programming was used to find out a mathematical model for drafting force from drafting process parameters on the drawing frame, which fits the experimental data as much as possible. The study used rayon fibers as the raw material in the mini-draw frame. The process parameters on the draw frame such as front roller speed, front roller draft, back roller speed and back roller draft as variables were investigated. The paper used the principle that there is linear relationship between drafting force and deformation from the strain gauges in the sensor. The data obtained from online measurement device was used for training and testing on the genetic programming. A comparison between experimental and predicted data was done. The results show very good agreement between the experimental and predicted values. Furthermore, this article shows that genetic programming can provide further use for setting up the machine process parameters without requiring an expert in the field.

Abstract: In this paper, a method of automatic inspection of silk spinning yarn fineness through image processing was developed. The acquired images were processed by image processing methods. Three thresholding methods were used and compared. The diameter and its CV value were obtained by processing the binary images. The results obtained were compared with measurements performed by means of EIB (Electronic Inspection Board). Yarn fineness and its CV value were obtained and the experimental results prove that the iterative method is more suitable for thresholding images to measure the silk yarn fineness.