• Elastomers and Composites
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• v.51 no.1
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• pp.56-62
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• 2016

The isothermal crystallization behaviors of blends of poly(ethylene naphthalate) (PEN) and a thermotropic liquid crystalline polymer (TLCP) were investigated by differential scanning calorimetry (DSC) as functions of crystallization temperature and blend composition. Avrami analyses were applied to obtain information on the crystal growth geometry and the factors controlling the rate of crystallization. The crystallization kinetics of the PEN/TLCP blends followed the Avrami equation up to a high degree of crystallization, regardless of crystallization temperature. The calculated Avrami exponents for PEN/TLCP revealed three-dimensional growth of the crystalline region in each blend. The crystallization rate of each blend increased as the crystallization temperature decreased, and decreased as the TLCP content increased. The crystallization of PEN in the blend was affected by the addition of TLCP, which acts as a nucleating agent.

• Proceedings of the Korean Fiber Society Conference
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• 2003.10a
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• pp.93-93
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• 2003

Electrically conducting polyaniline/cyanoethyl resin (PANI/Cyan) blends were prepared by in situ polymerization. The mechanical properties of the blend films increased with increasing cyanoethyl resin and the blend films have moderate conductivity.

• Polymer(Korea)
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• v.33 no.5
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• pp.509-513
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• 2009

For examining an effect of lithium bromide on structure and property of chitosan/fibroin blend, we investigated the structural characteristic of chitosan/fibroin blend films using solution with lithium bromide which was removed during a casting. The chitosan/fibroin blend formed a complex with the dissolved bromine/lithium ions. The crystalline phase of the complex was found in the blend film at LiBr concentration of 0.6 mol/L. The degree of crystallization was decreased with increasing the concentration of LiBr. The hydrated crystalline phase of chitosan was formed in the blend film that lithium bromide was removed in the process of casting by neutralization and osmotic action. The crystallinity of this film was increased largely as compared with that of the film without lithium bromide. The complexed blend film formed hydrogel absorbing plenty of water.

• Polymer(Korea)
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• v.33 no.6
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• pp.581-587
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• 2009

PLA/PEG blend fibers composed of poly (lactic acid) (PLA) and poly (ethylene glycol) (PEG) were prepared via melt blending and spinning for bioabsorbable filament sutures. The blend fibers hydrolyzed with the immersion in a phosphate buffer solution at pH 7.4 and $37\;^{\circ}C$ for 1~8 weeks. The effects of blending time, blend composition, and hydrolysis time on the weight loss and tensile strength of the hydrolyzed blend fibers were investigated. After hydrolysis, the weight loss of the blend fibers increased with increasing PEG content, blending time, and hydrolysis time. The tensile strength and tensile modulus of the blend fibers decreased with increasing PEG content, blending time, and hydrolysis time. Therefore, it can be concluded that the weight loss of the PLA/PEG blend fibers was less than 0.9% even at hydrolysis time of 2 weeks and their strength retentions were over 90%.

• Polymer(Korea)
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• v.28 no.3
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• pp.253-262
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• 2004

Poly(vinyl alcohol)(PVA)/chitosan blend films with non-toxicity, biodegradability, and biocom-patibility were prepared by solution casting. Variation of the physicochemical properties of the blend films was investigated through to several analysis methods. Examination of antibacterial properties revealed that bacterio-static ratios of all blend samples containing chitosan more than 10 wt％ were greater than 99.9％. Moisture regain was increased with increasing chitosan content but the degree of swelling was decreased. Up to chitosan content 15 wt％t, the melting and crystallization temperature of blend films was increased with chitosan content. The blends containing chitosan content 10 and 15 wt％ gave melting temperature 229 and 228$^{\circ}C$, respectively. However, the melting temperature was decreased if chitosan content exceeded 20 wt％. The mechanical properties of the blend films were increased with increasing chitosan content in both dry and wet states. The blend film including 15 wt％ chitosan exhibited unusually high tensile strength.

• Polymer(Korea)
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• v.35 no.6
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• pp.543-547
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• 2011

A study has been done to enhance the mechanical properties and processability of electrically conductive polyaniline(PANI) without the polymer's structural alternation. Functionalized acid doped PANI (PANI-DBSA) was prepared by an emulsion polymerization, and dodecylbenzenesulfonic acid (DBSA) played both roles of surfactant and dopant. Also, PANI-DBSA was solution cast blended with high impact polystyrene (HIPS) to produce PANI-DBSA/HIPS blend film. The structure and electrical properties of the conducting polymer blends were observed through UV-vis and FTIR/ATR spectroscopy. A study of the blend was carried by focusing on observation of mechanical and electrical properties based on dispersibility and changes in polymer morphology. The conductivity of the blends was increased by increasing the content of PANI-DBSA, and the sudden increase of conductivity to $3.5{\times}10^{-4}$ S/cm was observed even under a low content of 9 wt%. There was a strong association of continuous network formation with percolation and conductivity in the conducting polymer blends.

• Korea-Australia Rheology Journal
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• v.16 no.3
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• pp.135-140
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• 2004

Morphological and rheological properties of the poly(methyl methacrylate) (PMMA) and polystyrene (PS) blends were studied by scanning electron microscopy (SEM) and advanced rheometric expansion system (ARES). From the SEM results, the PMMA-PS blends showed dispersed morphology and the particle size of the dispersed phase was quite small (0.1~0.6 $\mu\textrm{m}$ compared with other immiscible polymer blends. Values of the interfacial tension of the PMMA-PS blend were obtained from the Choi-Schowalter and the Palierne emulsion models using the storage modulus of the PMMA and PS, and found to be 1.0 and 2.0 mN/m, respectively. The interfacial tension between the PMMA and PS was also calculated from the Flory-Huggins polymer-polymer interaction parameter ($\chi$) and found to be from 0.98 to 1.86 mN/m depending on the molecular weight and composition. Comparing the values of the interfacial tension from the Flory-Huggins polymer-polymer interaction parameter and the values measured by oscillatory rheometer, it is suggested that the interfacial tension of the PMMA-PS blend obtained from the polymer-polymer interaction parameter are in good agreement with the values obtained by rheological measurements.

• Applied Chemistry for Engineering
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• v.4 no.3
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• pp.601-615
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• 1993

A series of polycarbonate(PC)/polyamide 6(PA6) blends were prepared by three different blending methods to investigate their compatibility. From the DSC results, all of these blends have two Tg's in their own Tg regions, and there was no significant depression of the melting point and the crystallization temperature of PA6. With respect to the microstructure of the blends by SEM, the phase separation occurred at very low blend compositions, PC/PA6=95/5 and 5/95, already. In addition, a method is proposed to determine the Flory-Huggins polymer-polymer interaction parameter(${\chi}_{12}$) in polymer blend systems by using the experimentally determined Tg's. The values of ${\chi}_{12}$ obtained were 0.0381, 0.0411, 0.0418, for solution casting, solution precipitation, and extrusion blending methods, respectively. These values were higher than the critical value of ${\chi}_{12}$,($({\chi}_{12})_c$, 0.0271). Therefore it was concluded that the PC/PA6 blend system have little compatibility.

• Elastomers and Composites
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• v.23 no.2
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• pp.125-133
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• 1988

The thermal degradation of polymethyl methacrylate(PMMA) blend namely polymethyl methacrylate-polycarbonate(PMMA-PC) blend and polymethyl methacrylate-polystyrene(PMMA-PS) blend were carried out by isothermal method under air at several heating temperature from 220 to $270^{\circ}C$. Molecular weight changes during the thermal decomposition were monitored by means of the viscosity average molecular weight($\bar{M}v$). The viscosity average molecular weight was determined by Gel Permeation Chromatography(GPC). The dominant process in the degradation of PMMA-PC and PMMA-PS blend were main chain scission randomly due to weak links that may be distributed along the polymer backbone and the initial rate which the bonds are broken is not sustained. The infra-red spectra of degraded PMMA-PS blend show that the presence of aromatic ketone band at $1685cm^{-1}$. However, the infra-red spectra of degraded PMMA-PC blend show that the presence of hydroperoxide band at $3450cm^{-1}$. Thus indicating that the weak links are attacked by oxygen from the air and produce hydroperoxide or ketone. The activation energies of PMMA-PC blend and PMMA-PS blend were 18.2 and 17.9 Kcal/mol, respectively.

• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.289-290
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• 2003

Polymer blending constitutes a most useful method for the improvement or modification of the physicochemical properties of polymeric materials. So polymer blends have gained an increasing interest in both industrial and scientific fields. Some of the polymer blends exhibit unusual properties, unexpected from homopolymers. An important property of a polymer blend is the miscibility of its component, because it affects the mechanical properties, the morphology, its permeability and dogradation [1,2]. (omitted)