Suck Hyun Lee

Studies on the physical properties of modified starch-filled HDPE film

To improve the physical properties of starch-filled polyolefin, starch was modified into more hydrophobic material by the introduction of cholesterol unit, and the different starch-compositioned high-density polyethlene (HDPE) films were prepared with addition of either native starch or modified starch to compare their physical properties. The addition of either native starch or modified starch resulted in decreased crystallinities in all the different composite films containing starch. Interestingly, HDPE-blown films containing more than 10% native starch (HDPE/ST) showed a steeper decrease in crystallinity than correspondent HDPE containing the modified starch (HDPE/MS). Improvement of the dispersion and adhesion in HDPE/MS and HDPE/ST were also observed; but at high starch content, the HDPE/MS films showed higher tensile strength and elongation than the HDPE/ST. The degradation of HDPE/MS films in active sludge condition was much faster than that of the HDPE/ST films, although the degradation rate of HDPE/MS films in α-amylase condition were slower than the one of HDPE/ST films.

Continuous Nanofibers Manufactured by Electrospinning Technique

In this paper, we report a modified technique for the production of oriented continuous nanofibers instead of non-woven mats using a rapidly rotating collection device. We are interested in retaining physical properties such as electrical conductivity of fiber bundles in their axial direction. The experiments were performed using polyethylene oxide (PEO)|and its blend with polyaniline (PANI). According to the results, a typical fiber with a uniform diameter of about 100 nanometer was produced. The fibers from the PEO/ CHCl3 solution show high crystallinity and good orientation whereas the fibers from the blend solution of PEO/PANI/m-cresol and CHCl3 show no preferred orientation. However, the fibers of the blend exhibit high electrical conductivity of 33 S/cm for a fiber bundle at a PANI level of 50 %.

Micro-Chemical Structure of Polyaniline Synthesized by Self-Stabilized Dispersion Polymerization

A variety of NMR techniques were applied to the micro-chemical structural characterization of polyanilines prepared via an efficient synthetic method in a self-stabilized dispersion medium in which the polymerization was conducted in a heterogeneous organic/aqueous biphasic system without any stabilizers. Here, the monomer and growing polymer chain were shown to function simultaneously as a stabilizer, imparting compatibility for the dispersion of the organic phase, and as a form of flexible template in an aqueous reaction medium. Polymerizations predicated on this concept generated polyanilines with a low defect content: solution state13C-NMR and solid13C DD/CP/MAS spectroscopy indicated that the synthesized HCPANi and its soluble derivative, HCPANi-t-BOC, evidenced distinctly different NMR spectra with fewer side peaks, as compared to conventionally prepared PANis, and the complete structural assignments of the observed NMR peaks could be determined via the combination of both 1D and 2D techniques. Ortho-linked defects in HCPANi were estimated to be as low as 7%, as shown by a comparison of the integration of the carbonyl carbon resonance peaks.

Interfacial component of glass fiber in ternary composites of GF/PC/PP: effect of the preferential encapsulation of glass fiber

We investigated the encapsulation phenomena of glass fibers for a ternary composite system of glass fiber, polycarbonate and polypropylene by impregnating fibers with a selected resin using a newly developed process. On the basis of our observations of the morphology and mechanical properties, we report that viscosity ratio may very likely play an important role in the final interfacial structure of this system and that the improved wetting of fibers by preferential encapsulation would be a good approach in cases where the combinations of the resins or processing conditions lead to the similar relative melt viscosity of the component resins.

Studies on the degradable polyethylenes: Use of coated photodegradants with biopolymers

Three degradable polymer materials such as starch-polyethylene (PE) binary blends, PE containing starch and a photoactivator, and PE containing starch and a photoactivator which was coated with gelatin were prepared and their degrees of photodegradation and/or photodegradation after biodegradation were investigated. The addition of the gelatin-coated ferric salt in PE extended the induction period of degradation and accelerated photodegradation after the removal of coating material by biodegradation. This result suggested that the degradation rate of PE could be controlled if more powerful photoactivators and/or coating material are developed and their contents are optimized.

Formation of Hydrophobic and Water-Repellent Surface on Polyester Fibers using Ar/Hexamethyldisiloxane Plasma at Atmosperic Pressure

In this study, surface modification of polyester fibers with high water repellency was obtained by plasma treatment. Polyester fibers with water repellency were treated with atmospheric pressure middle-frequency (MF) plasma system using Ar and hexamethyldisiloxane (HMDSO). Ar gas has been used as the carrier gas. The surface morphologies of plasma-treated fibers were characterized by scanning electron microscopy (SEM). The Fourier transform infrared (FTIR) spectrometry was carried out to analyze the chemical composition of the polymer surface.

Dielectrophoretic technique for the preparation of density gradient polymers doped with a dipolar modifier

The dielectrophoretic technique was used to prepare density gradient polymers, polystyrene doped with a dipolar modifier, diphenyl sulfide. We have measured concentration gradients of the dopant by UV/Vis spectroscopy as a function of time in a nonuniform electric field. Measured concentration data at different positions of the sample confirmed that a concentration gradient arose after a nonuniform electric field was applied to the system, these data were used to compare the concentration profile with that predicted by the dielectrophoresis equation.

Polynucleotide Analogues: Synthesis and Physicochemical Properties

Much attention has been paid to the synthesis of polynucleotide analogues as model compounds for natural ones over last decade in an effort to elucidate functions of nucleic acids in the biological systems. More recently analogues themselves were found to show biological activities, arousing hopes for their utilization in chemotherapy as polymeric drugs