Seong Baek Yang

Electrospinning Fabrication of Poly(vinyl alcohol)/Pullulan/TiO 2 Nanofibers

Poly(vinyl alcohol)(PVA)/pullulan/titanium dioxide(TiO2) composite nanofibers were produced at different TiO2 concentrations(1 and 3 wt.%) using the electrospinning method. The parameters of electrospinning including polymer contents, voltage and tip-to-collector distance(TCD) were optimized for fabrication process. The study showed that the best condition to make PVA/pullulan nanofiber and effect of TiO2 nanoparticles. The PVA/pullulan/TiO2 nanofibers were characterized by scanning electron microscope(SEM), transmission electron microscope(TEM), Thermogravimetric analysis (TGA) and X-ray diffraction(XRD).

Surface Properties of a Novel Poly(vinyl alcohol) Film Prepared by Heterogeneous Saponification of Poly(vinyl acetate) Film

Almost general poly(vinyl alcohol) (PVA) films were prepared by the processing of a PVA solution. For the first time, a novel poly(vinyl alcohol) (PVA) film was prepared by the saponification of a poly(vinyl acetate) (PVAc) film in a heterogenous medium. Under the same saponification conditions, the influence of saponification time on the degree of saponification (DS) was studied for the preparation of the saponified PVA film, and it was found that the DS varied with time. Optical microscopy was used to confirm the characteristics and surface morphology of the saponified PVA film, revealing unusual black globules in the film structure. The contact angle of the films was measured to study the surface properties, and the results showed that the saponified PVA film had a higher contact angle than the general PVA film. To confirm the transformation of the PVAc film to the PVA film, 1H nuclear magnetic resonance spectroscopy, X-ray diffraction measurements, differential scanning calorimetry, and Fourier-transform infrared spectroscopy were employed.

Effect of Saponification Condition on the Morphology and Diameter of the Electrospun Poly(vinyl acetate) Nanofibers for the Fabrication of Poly(vinyl alcohol) Nanofiber Mats

Novel poly(vinyl alcohol) (PVA) nanofiber mats were prepared for the first time through heterogeneous saponification of electrospun poly(vinyl acetate) (PVAc) nanofibers. The effect of varying the saponification conditions, including temperature, time, and concentration of the alkaline solution, on the morphology of the saponified PVA fibers were evaluated by field-emission scanning electron microscopy. At 25 °C, the saponified PVA fibers exhibited a broad diameter distribution. The average fiber diameter, however, was found to decrease with increasing saponification temperature. When the saponification time was increased from 6 to 30 h, the average fiber diameter decreased gradually from 1540 to 1060 nm. In addition, the fiber diameter and morphology were also affected by the concentration of the alkaline saponification solution. The most optimal conditions for fabrication of thin, uniform, and smooth PVA nanofibers corresponded to an alkaline solution containing 10 g each of NaOH, Na2SO4, and methanol per 100 g of water, a temperature of 25 °C, and a saponification time of 24 h.

Novel Natural Polymer/Medicinal Plant Extract Electrospun Nanofiber for Cosmeceutical Application

Zein produced from maize is a hydrophobic protein, which holds great potential for a number of industrial applications, for example, food packaging, pharmaceutical, cosmetic, and biomedical industry. Sorghum, known as important cereal crop worldwide, is a good source of various phytochemicals such as tannins, phenolic acids, anthocyanins, phytosterols, and policosanols, and these phytochemicals have great impact on human health. Poria cocos, a well‐known traditional East‐Asian medicinal plant, is found around the roots of pine trees in Korea and China. As a rapid and efficient process, electrospinning has drawn huge interest among scientists to produce nanostructured polymer materials with excellent properties. In this work, we studied the influence of co‐solvent ratio and concentration of zein/medicinal plant extract on the morphologies of nanostructured zein/medicinal plant extract nanomaterials prepared by electrospinning technique from ethanol/water solution. The zein/medici‐ nal extract nanofibers were characterized by field‐emission scanning electron micro‐ scopy, transmission electron microscopy, thermogravimetric analysis, and differential scanning calorimetric technique. And we were to incorporate medicinal plant resources into the electro‐spun zein nanofibers by electrospinning technique to investigate the effect of medicinal extract on the morphologies, antibacterial, antioxidant, and other properties. Zein/medicinal plant extract might have a practical use as a new preserva‐ tive for cosmeceutical applications.

Fabrication of Highly Aligned Poly(Vinyl Alcohol) Nanofibers and its Yarn by Electrospinning

In the conventional electrospinning method, fibers are randomly deposited and form nonwoven structures; however, highly aligned microor nanofiber and its yarn may only be applicable for the fields, including composites, clothing, textiles, and microelectronics. The elementary principle to obtain uniaxially arranged nanofiber array is to regulate the electric field distribution by using assistant electrode or modified collecting device. The potential applications of conventional electrospun poly(vinyl alcohol) (PVA) fiber in the preparation of ultrafine separation filters, biodegradable mats, etc., have been described by many researchers. Highly aligned PVA nanofibers were prepared using a modified electrospinning process at the optimum conditions, and a twister added modified electrospinning apparatus was used to prepare twisted nanofiber yarn. The diameter and arrangement of the electrospun PVA nanofibers were characterized using FE-SEM. To study the effect of applied voltage and rotational velocity on the alignment rate of the nanofibers, different voltages and rotational velocity were applied during modified electrospinning, keeping other parameters unchanged. To measure the melting temperature and crystallinity of aligned nanofibers, differential scanning calorimetry and X-ray diffraction measurement were performed, respectively. The fabricated highly aligned nanofiber and its yarn might have a practical use of devices for microelectronics.

Optimum Conditions for the Fabrication of Zein/Ag Composite Nanoparticles from Ethanol/H2O Co-Solvents Using Electrospinning

The optimum conditions for the fabrication of zein/Ag composite nanoparticles from ethanol/H2O cosolvents using electrospinning and the properties of the composite were investigated. The zein/Ag nanoparticles were characterized using field-emission scanning electron microscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermogravimetric analysis. The antibacterial activity of the zein/Ag composite nanoparticles was also investigated. The XRD patterns and TEM images indicate the coexistence of a zein matrix and well-distributed Ag nanoparticles.

Effect of Density Variation of High Tenacity PET Interlace Yarn on the Physical Properties of Pack Style Shock Energy Absorber

Fall-arrest systems(maximum arrest force and allowable free-fall) have been widely applied to provide a safe stop during fall incidents for various industrial activities. Fabric structure affects on the mechanical properties of shock energy absorber. The object of this study is to perform the basic research for the evaluation of the capacity of fall arrest energy absorber in relation to the different interlace yarn density. In this work, pack style energy absorber was prepared by weaving 10 types(Interlace yarn density used high tenacity PET 1000D : 60, 59, 58, 57, 56, 55, 54, 53, 52, 51). The paper presents the results of theoretical investigations of the performance of adjustable absorber during fall arrest. Dynamic load tests based on the EU fall protection equipment standard(CE : EN355:2002) were conducted. Results showed that the maximum arrest force by dynamic load test of energy absorber was satisfied with global standard(below 6,000N). Also, Maximum allowable free-fall of energy absorber showed below 1.75m.