Advanced Materials Research Vol. 796

Abstract: Polystyrene (PS) ultrafine fibrous membranes were prepared by electrospinning. The effects of PS molecular weightand auxiliary electrode on jet splitting behavior, fiber morphology and mechanical properties of the fiber nonwovens were investigated. The jet splitting behavior was examined by high-speed camera, the fiber morphology was observed with scanning electron microscopy, the mechanical properties of the membranes were measured with universal tensile machine. The results showed that, the stable jet length, the fiber diameters and the density of the mats are all increased in the presence of auxiliary electrode. The increase of polymer molecular weight postpones jet splitting, and enlarges fiber diameters and elevates the tensile strength of the membranes. Heat treatments of the membranes both at atmospheric pressure and high pressure significantly promote conglutination among filaments and heighten the tensile strength. The presence of solvent molecules in the fiber mats impairs mechanical properties to some extent when the two heat treatment modes are contrasted.

Abstract: In fiber reinforced thermosetting plastic (FRP) the fiber volume fraction is always up to 60 percent, but in fiber reinforced thermoplastic (FRTP) it is low to about 30 percent which greatly limit their performance. In this paper, for increasing the fiber volume fraction of thermoplastic composite, a new impregnation method for molding continuous fiber reinforced thermoplastic was explored; the fiber volume fraction was significantly raised to 60 percent which is equal to that of FRPs. Then the tensile property was investigated and made a contrast with FRP with the same reinforcement fiber. The results showed that both the FRP and FRTP composites have the similar tensile properties and indicated that the molding method is effective for FRTP manufacture.

Abstract: Electrospinning is one of the few simple and effective ways to produce nanofibers, which can be used in various fields. However, the common assembled nanofiber mats are limited in some areas, so static bath was used as the negative collector to produce nanofiber yarns. In order to improve the yields, a novel multi-needle electrospinning using static bath collector was employed, the spinning state and the nanofiber orientation of the as-spun yarns in different numbers of spinning needles are described in details. The results showed that the critical voltages, keeping the electrospinning process stable, increased from 21KV to 28KV with the number of spinning needles increasing from 1-5. Nevertheless, the orientation degrees of the nanofibers in the yarn decreased from 94.40% to 81.29%. Based on the SEM images and orientation degrees of the yarns, the alignment of the nanofibers along the axis of the yarn was seemed still pretty well when the 1-4 needles used. But it was seemed a little disordered when the number of needles reached 5, which was not so well for applications.

Abstract: High-strength uniaxially-aligned electrospun nanofibers were prepared from PVA reinforced by modified hydrophilic multi-walled carbon nanotubes (MWCNTs). In order to get a homogeneous spinning solution, a one-step process using ammonium persulfate (APS) as oxidant was employed to fabricate water-soluble MWCNTs, and then they were dispersed in a 10 wt% PVA aqueous solution. We utilized this macroscopically homogeneous dispersion to produce nanofibers mat by electrospinning with an ultra-high-speed rotating cylinder as a collector. SEM image shows that the aligned degree of the fibers increases along with the increase in rotating speed. When the speed is up to 2000 rpm, the electrospun nanofibers are nearly uniaxially aligned. The tensile test results suggest that a small amount of MWCNTs dramatically enhanced the tensile strength of PVA fibers.

Abstract: To achieve continuous yarns formed of nanosized filaments during electrospinning, a chemical liquid in a container was used in this study as the collector (i.e. the negative electrode) to convert nanofiber filaments into yarns. This study focuses on analyzing the impact of the chemical solutions employed in the negative electrode on the Taylor cone and trajectory of the fluid jet during the process of electrospinning. The results indicated that only 5wt peregal O solution produced non-interrupted filaments so the spinning system can work continuously for up to 10 hours. Also, the results showed that both the angle and volume of Taylor cone enlarged along with the increase of the electrical conductivity of the negative electrode. When changing the spinning voltage, both the volume of the Taylor cone and the shape of the spinning jet changed significantly.

Abstract: In this article, the yield of mulberry cocoon, the output of raw silk, the output of silk fabric, the consumer price index, the GDP per capita and the per capita income from 1999 to 2011 were analyzed for their principal components on the major production areas of cocoon and silk in China. The principal component analysis can ensure the smallest loss of the original data, to replace the multi-variables with a few synthetic variables, to simplify the data structure, and objectively determine the weights. The distances and similarities between provincial principal components, which were regarded as multivariable time series, were analyzed and computed, and clustering analysis were carried out. The result can be used as a basic reference for the industrial configuration and structural adjustment of silk in China.

Abstract: PVDF nanofibrous membranes were successfully prepared by electrospinning in this paper, and the component solvent of DMF/acetone was used. The concentration of PVDF and the volume ratio of component solvents of DMF/acetone were the most important variables to affect the morphology, diameter and uniformity of the nanofibers. The concentration of spinning fluid changed from 10 wt% to18 wt% and the volume ratio of DMF/acetone ranged from 2/8 to 8/2. The results of the study showed that the better nanofibrous membrane was prepared when the concentration of PVDF was 12 wt% and the ratio of component solvent DMF/acetone was 6/4. At this moment, the morphology and contact angle of PVDF membrane were better in comparison with other groups. The contact angle, waterproof properties, air permeability were measured, which indicated that the PVDF nanofibrous membrane showed a good air permeability and had an excellent waterproof properties at the same time. In the meantime, by changing the thickness of membrane, we could analyze the relationship between the thickness of the membrane and its breathability and waterproofness.

Abstract: A systematic study on molecular structure of Poly (DL-lactide-co-glycolide) (PLGA) films by the methods of being chemically immobilized onto self-assembled monolayers (SAMs) and spin coating using Fourier transform infrared spectroscopy (FTIR), sum frequency generation (SFG) vibrational spectroscopy is reported. Especially, a surface sensitive second order nonlinear optical technique, SFG vibrational spectroscopy, was applied to study molecular structure on PLGA films. It is shown that the more chemical groups of PLGA thin films with being chemically immobilized have orientation than that of PLGA films made by spin coating on the basis of SFG vibrational spectroscopy data. The characterization of the other analytical techniques indicates similar results. This work will be an important step for future biomaterials design and understanding biosensors, biocompatibility and biomacromolecule (e.g. proteins and peptides) activity.

Abstract: The transfer paper used in novel silk transfer printing with reactive dyes was prepared by coating pastes. Water-soluble polyester named ES-1, carboxymethyl cellulose (CMC), alkali and hygroscopic agent were used according each function and mixed to prepare the pastes. The solid content of ES-1 and CMC in the pastes plays a crucial role in the face K/S value of prints. The color fastness of washing and rubbing for prints are above grade 4~5 and ES-1 is hardly adhered on printed fabrics.

Abstract: Based on the current color fastness standard of textiles at home and abroad, this paper gives a comparative analysis of the testing standard of related indicators, discuss the major color fastness of textiles including color fastness to water, to perspiration, to rubbing, to laundering. The quantified data of the sample test results show that there are some differences among the test methods, the equivalent of quantitative values and the requirements of indicator in GB, ISO, AATCC.