• Polymer(Korea)
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• 제27권2호
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• pp.129-134
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• 2003

It has been known that the intercalation of long alkyl chains in montmorillonites (MMT) increased the hydrophobicity as well as gallery spacing of UT, which has influenced on the exfoliation behavior of various polymers. A series of organophilic MMTs were synthesized from the water/isopropyl alcohol solution of MMT with ammonium salts of various alkyl amines. The properties of obtained MMTs such as thermal decomposition temperature, gallery spacing as well as hydrophobic property were investigated. The X-ray diffraction experiments on organophilic montmorillonite demonstrated that the increase of length of alkyl substituent resulted in increase in the spacing between silicate layers, which was ranged from 13.1 to 29.4 $\AA$. On the other hand, introduction of (di-, tri-) alkyl substituents in ammonium salts decreased water absorption of organophiplic montmorillonite to 2.7%.

• Polymer(Korea)
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• 제27권2호
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• pp.159-166
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• 2003

For the purpose of obtaining surface-anionized poly(vinyl alcohol) (PVA) hydrogel beads, vinyl acetate(VAc) and methacrylic acid(MMA) were copolymerized by the suspension polymerization technique and followed by the saponification. It was confirmed by $^1$H-NMR that the copolymerized microspheres contained carboxylic acid groups in their surface. poly(VAc-co-MAA) microspheres were completely saponified in the heterogeneous system. The saponification reaction was laster than that of PVAc microspheres. We observed the swelling property of saponified PVA microspheres treated in the acidic solution and in the alkaline solution successively. Saponified microspheres shrank in acidic solution and swelled in alkaline solution respectively, which was reversible. from the result, saponified microspheres were highly water-absorbing hydrogel beads and were certified -COOH group at their surface by $^1$H-NMR and FT-IR.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 추계학술대회 초록집
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• pp.176.2-176.2
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• 2011

전 세계는 화석연료의 과사용으로 에너지 고갈과 환경오염의 문제에 직면하고 있으며, 자연과 공존하며 지속성장할 수 있는 신재생에너지의 이용확대에 대한 개발이 부각되고 있다. 이에 따라 지속적인 발전과 함께 에너지보존 및 효율적인 환경보존을 위한 대체 가능한 새로운 에너지의 개발에 관심이 모아지고 있다. 최근 부각되고 있는 바이오에너지(바이오에탄올, 바이오디젤, 바이오가스 등)를 생산하는 여러 가지 새로운 바이오매스 중 해조류는 이산화탄소 흡수 능력이 매우 뛰어나고, 에너지 저장성이 우수하다는 장점이 있다. 본 연구에서는 새로운 바이오매스원인 해조류의 부산물의 표면 특성 및 바이오복합재료의 보강재로써의 이용가능성에 대해 분석하였다. 바이오복합재료에서 소수성인 고분자와의 상호보완적 계면 결합은 보강재의 중요한 특성 중 하나이다. 해조류 부산물의 표면을 화학적 처리함으로써 폴리머 매트릭스와 해조류 부산물 사이의 계면결합이 향상됨을 기대할 수 있으며 이에 따라 해조류 부산물을 보강재로 사용한 바이오복합재료의 기계적 강도 또한 향상됨을 기대할 수 있다. 본 연구에서는 원자힘현미경(Atomic force microscope; AFM)을 사용하여 해조류 부산물의 화학적 처리에 따른 표면특성을 관찰하였으며, 친환경적인 바이오매스인 해조류 부산물을 바이오복합재료의 보강재로써의 이용가능성에 대해 연구함으로써, 지구온난화의 주원인인 온실가스 발생을 줄이고, 자원고갈이라는 에너지 위기를 극복할 수 있는 친환경적인 대안을 제시 할 수 있다.

• Polymer(Korea)
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• 제30권2호
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• pp.124-128
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• 2006

Heavy weight of the camouflage materials was always the main problem. To solve it, the low infrared emissivity fibers with the radar absorbing property (LIFR) were prepared. The low infrared emissivity fibers (LIF) were firstly melt-spun by co-extrusion of polypropylene (PP) and PP/various fillers master-batches using general conjugate spinning. The infrared emissivity of LW with AA and ZnO was decreased respectively compared with that of pure polypropylene fibers. The infrared emissivity of LIF with 15 wt% Al and 2 wt% ZnO in the sheath-part can reach 0.58. To improve LIF radar absorbing property, LIFR was prepared by filling the 50 wt% ferrite and bronze in the core-part of LIF. The radar absorbing efficacy of LIFR was good and the infrared emissivity was low. For the characterization, fiber electron intensity instrument and differential scanning calorimetry (DSC) were used for the analysis of mechanical properties, thermal and crystallization behavior of the spun-fibers. Scanning electron microscopy (SEM) was carried out to observe the particle distribution of the bicomponent fibers.

• Polymer(Korea)
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• 제30권2호
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• pp.182-186
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• 2006

Due to their periodic helical structure, cholesteric liquid crystals (CLC) have a unique ability to selectively reflect light. CLC films reflecting a broad wavelength band were prepared by inducing a pitch gradient in CLC layer through a phase separation. The reflection bandwidth of the CLC cell was broaden as irradiation light intensity decreased and as the amount of the UV absorbing dye increased. Initial reflection bandwidth of 50 nm was broaden to 300 nm Various pitch distributions in the CLC cell was observed using SEM and ATR-IR technique was used to prove that the pitch distributions are induced through the phase separation.

• Polymer(Korea)
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• 제26권4호
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• pp.462-467
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• 2002

Blends of polymethylmethacrylate (PMMA) with polyvinylidenefluoride (PVDF) were prepared by melt mixing and investigated for optical waveguide devices by using hot embossing process. The glass transition temperatures ($T_g$) of the blends were decreased with increasing PVDF contents. However, the crystalline of PMMA/PVDF blends was not appeared by DSC and XRD due to miscibility between PMMA and PVDF. Shear viscosities and refractive indices of the blends were decreased with increasing PVDF contents. Optical transmittances and absorption losses of the blends were improved with increasing PVDF contents. This is due to a decreasing of polarizability of molecules by fluorine molecule in the PVDF.

• Polymer(Korea)
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• 제35권5호
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• pp.390-394
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• 2011

Effects of silver nanoparticles on the polymerization rate and morphology of poly(vinyl acetate) (PVAc)/silver microspheres prepared by suspension polymerization of VAc were investigated. Scanning electron microscopy, transmission electron microscopy, X-ray diffraction and atomic absorption spectrometry were used to characterize the morphology and properties of the PVAc/silver microspheres. Due to the change of hydrophilicity of silver nanoparticles, appearance of the microspheres having golf ball-like convave surfaces was observed. Under controlled concentration of surfactant, PVAc/silver microspheres with various hollow structures were synthesized. In the case of silver nanoparticles modified by surfactant, the polymerization rate increased slightly. PVAc/silver microspheres with a conversion up to 80% were prepared via suspension polymerization.

• Polymer(Korea)
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• 제36권5호
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• pp.662-667
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• 2012

Poly(ethylene terephthalate) (PET) base films with high light transmittance have been used for the substrate of various functional films in the flat panel display. The effects of the reflective index of coated films, the roughness of the film surface and the content of inorganic silica particles on the light transmittance were studied in this article. Light transmittance was increased by coating a water soluble resin with a low reflective index at an optimum thickness. The roughness of the film did not affect light transmittance when the Ra of the film surface was less than a quarter of the wavelength of incident light. Inorganic silica particles decreased light transmittance due to their absorbance and scattering of the incident light.

• Polymer(Korea)
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• 제26권6호
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• pp.821-828
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• 2002

Regular and highly interconnected macroporous poly(L-lactic acid) (PLLA) scaffolds with pore size of 10∼300 ㎛ were fabricated through thermally induced phase separation of a PLLA-dioxane-water ternary system in the presence of a small amount of Pluronics. Addition of Pluronics to the ternary system raised the cloud-point temperature curve in the order of P-123< F-68< F-127. The Pluronics act as nuclei for the phase separation. This assistance is enhanced with increasing length of the hydrophilic PEO blocks in the Pluronics molecules. Liquid-liquid spinodal phase separation was induced at higher temperatures in the systems containing Pluronics because the spinodal region is raised to higher temperature. The absorption of Pluronics onto the interface stabilizes a macro scale structure and increases the interconnection of pores.

• Polymer(Korea)
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• 제39권2호
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• pp.256-260
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• 2015

The addition of montmorillonite (MMT) in the UV curable polyurethane diacrylate based resins was investigated to fabricate nanocomposites with improved mechanical properties and water sorption behavior using different photoinitiator systems. As a result, it was observed that 1 wt% of clay loading fairly improved tensile resistance and water uptake behavior. It can be also confirmed that dual photoinitiator system consisted of benzyldimethyl ketal and bisacyl phosphine oxide exhibited enhanced energy absorption band 340~450 nm even with 3 wt% of MMT concentration, which may affect the curing behavior of nanocomposite especially in our UV lamp system.