• Polymer(Korea)
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• v.30 no.5
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• pp.380-384
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• 2006

Polyhedral oligomeric silsesquioxanes (POSS) were used as starting materials for the preparation of hybrid materials with polystyrene (PS). Optically transparent hybrids were obtained in a wide range of weight ratios when phenyl groups were introduced to each corner of the silsesquioxane. In contrast, as cyclohexyl groups were introduced, the obtained hybrid materials with PS resulted in turbid films. The aromatic (${\pi}-{\pi}$) interaction was confirmed to be a quite effective tool for the synthesis of organic-Inorganic polymer hybrids with POSS. The obtained homogeneous and transparent hybrid films could be dissolved in solvents and East again without any separation. The homogeneity of polymer hybrids with POSS was supported by the result of scanning electron microscopy (SEM), X-ray diffraction (XRD), and differential scanning calorimetry (DSC), which demonstrated a nanometer-level integration of PS and POSS.

• Polymer(Korea)
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• v.24 no.5
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• pp.713-720
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• 2000

A polymer/iodine complex film was prepared using syndiotactic poly(vinyl alcohol) (s-PVA) with number-average degree of polymerization of 900 and syndiotactic diad content of 63.1%. In comparison with atactic-PVA/iodine films, degree of polarization of the s-PVA/iodine film was improved up to over 99% although a lower transmittance was obtained. By soaking in iodine/potassium iodide aqueous solution of a lower iodine concentration and subsequent drawing by 4 times, s-PVA/iodine film of a higher transmittance and degree of polarization was produced. The degree of iodine desorption of the s-PVA/iodine film in water were very low. The crystallinity and the d-spacing and crystal size of (100) plane increased at the early stage of soaking time, however, remained constant or decreased slightly with increasing soaking time. In consequence, s-PVA/iodine complex formation took place mainly inside crystal region at the initial stage of soaking time, whereas it occurred outside crystal region or physical adsorption of iodine dominated after sufficient soaking.

• Polymer(Korea)
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• v.36 no.5
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• pp.643-650
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• 2012

In order to improve the thermal stability of polyurethane, we synthesized poly(adipate urethane) (PAU) and three PAU composites, PAU/30B (2.7 wt% 30B), PAU/MP (2.2 wt% MP), PAU/30B/MP (2.2 wt% 30B and 2.2 wt% MP), from poly(oxydiethylene adipate)-diol (PAD), 4,4'-methylene diphenyl diisocyanate (MDI), Cloisite 30B (30B), and melamine phosphate (MP). 30B and MP were introduced into the reactant mixture at the initial stage of the esterification between adipic acid and diethylene glycol, so 30B and MP were evenly dispersed in the PAU composites for long period. At temperatures lower than $250^{\circ}C$, the PAU composites were degraded faster than pristine PAU, mainly due to the decomposition of 30B and MP. At higher temperatures, the 30B and MP enhanced the thermal stability of the PAU composites. Compared with the pristine PAU, the thermal decomposition rates of the PAU composites decreased by 13~17%. In air, the residual weights of PAU/30B, PAU/MP, and PAU/30B/MP were 2.4, 2.3, and 7.3 wt% at $700^{\circ}C$, respectively.

• Polymer(Korea)
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• v.35 no.1
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• pp.47-51
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• 2011

In this study, illite, an environmental friendly, low cost, and high aspect ratio additive, was used to improve flame retardant property of epoxy and it was fluorinated to enhance dispersion of hydrophilic illite in hydrophobic epoxy by introducing hydrophobic functional groups. Fluorination of illite enhanced illite dispersion ill epoxy solution before curing and that in the complex after curing. These enhanced dispersions were attributed to the increased affinity of illite to hydrophobic epoxy solution induced by fluorination of illite and the increased intercalation of epoxy polymer or exfoliation of illite by epoxy curing. Hence, limited oxygen index(LOI) of fluorinated illite/epoxy complex increased by 24%, compared to that of epoxy, suggesting that the preparation of fluorinated illite/epoxy complex increased their flame retardant properties.

• Polymer(Korea)
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• v.33 no.3
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• pp.243-247
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• 2009

Cellulose diacetate (CDA) was plasticized with triacetine (TA) and epoxidized soybean oil (ESO) in a high speed mixer. Composites of plasticized CDA and zeolite were prepared by a melting process. The $T_g$ value, $106^{\circ}C$ of the plasticized CDA was confirmed by DMA analysis. The $T_g$ value of the CDA with 50% zeolite was $125^{\circ}C$. As the content of zeolite was increased from 10 to 50% the modulus of the composite was increased from 1.7to 3.6 GPa by two times over the plasticized CDA, and its tensile strength was increased to 62 MPa and then decreased down 51 MPa, and its elongation was increased to 10% and then decreased down 3.2%. In the SEM image, the compatibility between CDA and zeolite was observed. Increasing the amount of zeolite in the composites resulted in further enhancement of the $CH_3COOH$ absorption effects.

• Polymer(Korea)
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• v.37 no.5
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• pp.638-641
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• 2013

GNS/PVDF composites were prepared using graphite nanosheets (GNS) and poly(vinylidene fluoride) (PVDF) for flexible thermoelectric application. We measured the electrical conductivity, thermal conductivity and Seebeck coefficient of GNS/PVDF composites with different contents of GNS and then evaluated the thermoelectric properties of GNS/PVDF composites. The electrical conductivity of GNS/PVDF composites increased from 389 to 1512 S/m with increasing the content of GNS from 10 to 70 wt%. While the electrical conductivity dramatically increased, Seebeck coefficient and thermal conductivity did not show any big difference as the content of GNS increases. In this study, we demonstrated that GNS/PVDF composites improved the thermoelectric properties by decreasing the thermal conductivity due to the phonon scattering at the interfaces between polymer and GNS nanoplatelets.

• Polymer(Korea)
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• v.27 no.1
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• pp.40-45
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• 2003

In this work, the effect of different contents of $Fe_3O_4$ and temperature variation on the electrical conductivity ($\sigma$) in the polar acrylonitrile butadiene rubber (NBR)/$Fe_3O_4$ (magnetite) mixture system was investigated. It was found that the percolation threshold concept holds true for the conductive particle-filled composites where $\sigma$ indicates a nearly sharp increase when the concentration of magnetite in the mixture exceeds 22%. The temperature dependence of $\sigma$ was thermally activated below and at the percolation threshold ($P_c$). Magnetite acted as reinforcing and conductive filler for NBR. At room temperature and higher voltages, the electrical current was proportional to the square of voltage ($I{\propto}V^2$) for the composites which contain 30 phr of magnetite. Moreover, it was shown that the composites with magnetite of 50 phr showed the highest tensile strength and elongation at break, which was due to the formation of optimal physical interlock and crosslinking. The results of 100%, 200%, and 300% Young moduli said that the moduli are largely correlated with reinforcement effect of magnetite and viscosity of the blends from torque curve.

• Polymer(Korea)
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• v.33 no.1
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• pp.1-6
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• 2009

We report the template-based synthesis of well-dispersed CdS nanoparticles (NPs) in the interior of poly (2-acetamidoacrylic acid) (PAAA) hydrogel as a novel type of nanocomposite without particle aggregation via ion exchange in a aqueous system. As revealed by the TEM image analysis, the mean crystallite diameter of CdS NPs embedded in hydrogel composite was 4.5 nm, and the composite did not suffer any observable change after 6 months. Desorption/decomposition of CdS/PAAA hydrogel composite was studied by evolved gas analysis-gas chromatography-mass spectrometry (EGA-GC-MS), and thermogravimetric analysis (TGA) methods. From the TGA data, the thermal stability of the composite system increased by ca. 100 $^\circ$C and the content of CdS NPs in a dry composite gel was over 70 wt%. In addition, the chemical pathway was proposed for the entire decomposition process.

• Polymer(Korea)
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• v.37 no.6
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• pp.764-769
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• 2013

Starch was grafted by poly(methyl methacrylate) through the emulsion polymerization method. Modified starch/(acrylonitrile-butadiene rubber) (NBR) compounds were prepared by a latex blend method. The morphology, thermal properties and mechanical properties of the modified starch/carbon black/NBR composites were investigated with the change of starch concentration. The mechanical properties of the composites were improved by the addition of modified starch. But, when the concentration of modified starch was higher than 40 phr, the mechanical properties were deteriorated due to the poor dispersion of modified starch. At the same ratio of starch to carbon black, the composite showed a synergistic reinforcing effect by the good dispersion and high cross-linking density. In addition, the tensile strength, storage modulus, hardness, swelling and other properties were the best.

• Polymer(Korea)
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• v.34 no.4
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• pp.346-351
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• 2010

The mechanical properties of polypropylene (PP) composites, especially the effects of the filler shapes on the modulus were studied. The experimental results were investigated and compared with the theoretical approaches proposed by Lee and Paul and based on Eshelby's principle, which three dimensional ellipsoids were filled as filler and analyzed in terms of aspect ratio, ${\rho}_\alpha=a_1/a_3$ and ${\rho}_\beta=a_1/a_2$. The shapes of fillers were observed by SEM and aspect ratios were statistically calculated. Young's moduli in the longitudinal and transverse directions for barium sulfate whose shape was sphere ($\rho_\alpha=\rho_\beta=1$) had the same values, as predicted values. The modulus in the $x_1$ direction for a glass fibers increased as the filler content increased, while the modulus in the $x_3$ direction was increased relatively small. Furthermore, mica was also used to investigate the effects of the primary and secondary aspect ratios on the mechanical properties.