• Polymer(Korea)
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• v.31 no.4
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• pp.283-288
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• 2007

Polymer blends containing poly(acrylonitrile-butadiene-styrene) (ABS) and polycarbonate(PC) (70/30, wt%) with compatibilizer were prepared using twin screw extruder. Compatibilizers were prepared by reactive extrusion with the ABS, maleic anhydride(MAH) and dicumyl peroxide(DCP) using twin screw extruder In the ABS/PC (70/30) blends, tensile strength did not change significantly, but increased from 52.25 to 55.03 MPa when the ABS-g-MAH was added in the amount of 5 phr. From the results of rheological properties, storage modulus of the ABS/PC/ABS-g-MAH blends at low frequencies showed lager value than that of the ABS/PC(70/30) blend. From the results of the morphological properties of the ABS/PC(70/30) blend, it was observed that the drop size of the PC ranged from 1.2 to $1.5\;{\mu}m$ and did not change significantly with the addition of the ABS-g-MAH($1{\sim}10\;phr$). From the results of the storage modulus, complex viscosity, and tensile strength of the ABS/PC (70/30) blends, it is found that the ABS-g-MAH is an effective compatibilizer in the ABS/PC (70/30) blends when the ABS-g-MAH is added in the amount of 5 phr.

• The Korean Journal of Rheology
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• v.11 no.1
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• pp.18-27
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• 1999

Predicting the deformation behaviors of sheets in thermoforming processes has been a daunting challenge due to the strong nonlinearities arising from very large deformations, mold-polymer contact condition and hyperelasticity constitutive equations. Nonlinear numerical analysis is always required to face this challenge especially for realistic processing conditions. In this study a 3-D algorithm and the membrane approximation are developed for thermoforming processes. The constitutive equation is expressed in terms of the 2nd Piola-Kirchhoff stress tensor and the Cauchy-Green deformation tensor. The 2-term Mooney-Rivlin model is used for the material model equation. The algorithm is established by the finite element formulation employing the total Lagrangian coordinate. The deformation behavior and the stress distribution results of 3-D algorithm with various point boundary conditions are compared to those of the membrane approximation algorithm. Also, the slip boundary condition and the no-slip boundary condition are applied for the systems that have molds. Finally, the effect of sheet temperatures on the final thickness distribution is investigated for the ABS material.

• International Journal of Highway Engineering
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• v.16 no.2
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• pp.19-24
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• 2014

PURPOSES : The study objective was to evaluate rheology and physical properties of SBS-modified warm-mix asphalt (WMA) binders in comparison with hot-mix asphalt (HMA) binders. METHODS : Four different SBS polymers were used to prepare polymer-modified asphalt (PMA) binders, and three different warm-mix additives (WAD) were used to prepare a total of 12 WMA PMA binders. The kinematic viscosity was measured at 115, $135^{\circ}C$. The PG was determined using DSR and BBR. The pass/fail (P/F) temperatures for high and low PG grading were evaluated for HMA PMA and WMA PMA binders. RESULTS : PG 76-22 binders could be prepared by modifying the base binder (PG 64-22) using 4.5 wt% of SBS. The kinematic viscosity (KV) of SBS PMA was increased by 3 times higher than that of base asphalt. The SBS PMA with WAD showed 10% lower KV than that of the normal SBS PMA at $115^{\circ}C$ The high P/F temperatures showed almost no difference between HMA PMA and WMA PMA binders. The high P/F temperature showed very high correlations with KV ($R^2$ > 0.97). The result of SBS modification caused increase of low P/F temperature by $2.7^{\circ}C$ on average. CONCLUSIONS : Since the PMA with WAD showed 10% lower KV than normal (HMA) PMA at $115^{\circ}C$, reducing PMA mixture temperature down to a WMA level was possible in this study. The higher KV binders showed the higher P/F temperature. There was almost no change in high P/F temperature due to the use of WAD. The SBS PMA, showing an increased low P/F temperature, might show somewhat poorer performance at low-temperature, even though the lower PG grade was staying at the same level, i.e., $-22^{\circ}C$.

• Journal of Digital Convergence
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• v.13 no.8
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• pp.369-374
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• 2015

In this study, by combining a unique purpose and additional aspects of ultrasonic transmission media, a development potential on a new ultrasonic transmission media was sought. The rheological characteristics and the manufacturing cost for each manufactured formulation were compared and analysed with ready-made. An ultrasonic transmission media is to have different functional characteristics according to the following formulation, it was the best in rheological value, low viscosity emulsion with the oil gel. Polymer hydro gel is can be manufactured at low cost compared to other formulations. Emulsion which shows a sharp viscosity difference according to the components of oil and water had a big difference in manufacturing cost. This study can be utilized as the fundamental data on the ultrasound transmission media equipped with expertise in various areas of ultrasound.

• Macromolecular Research
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• v.17 no.5
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• pp.332-338
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• 2009

Rheological behavior of natural hydrogel produced from seeds of three Salvia spp. (S. miltiorrhiza (SM), S. sclarea (SS), S. viridis (SV)) was investigated by using a Rheometer equipped with a cone and plate geometry measuring system under never-dried condition. Different chemical contents of such hydrogels give significant effects on their rheological properties. Because of incomplete penetration of water inside the hydrogels after drying before-dried hydrogels were used for rheological analysis. To know molecular interactions which predominated in the gel formation, some constituents were externally added to the 1.0% (w/w) hydrogel. Addition of urea to disrupt hydrogen bonds reduced 3.4-67% viscosity of the untreated hydrogels and changed viscoelastic properties from gel to liquid-like behavior. Neutral salts added to the hydrogel solution at 0.1 M also lowered the viscosity in a manner related with increase in size of cations and temperature. Changing from gel state to liquid-like state was also easily confirmed by oscillation measurement (storage, G', and loss, G", modulii) typically observed in the cases of potassium sulfate and potassium thiocyanate. Influence of pH variation on the viscosity explained that weak alkaline condition (pH 8-9) creates a higher resistance to flow due to increasingly electrostatic repulsions between negative charges ($COO^-$) Importance of calcium bridges was also demonstrated by recovery of viscosity of the hydrogels by addition of calcium after acidification. The summarized results indicate that electrostatic repulsion is a major contributor for production of hydrogel structure.

• Applied Biological Chemistry
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• v.39 no.3
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• pp.165-171
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• 1996

The rheological properties of biopolymers produced by Bacillus sp. K-1 and its mutant strains(KM-21, KM-83) were studied. Apparent viscosity of biopolymers decreased as rising the temperature. The biopolymer produced by KM-21 strain showed 1.7 times low viscosity, 2.7 times low viscosity by K-1 and 1.9 times low viscosity by KM-83 at $80^{\circ}C$ compared with at $20^{\circ}C$ respectively. The viscosity of biopolymer solution also increased with increasing the polymer concentration and showed pseudoplastic characteristics which is high temperature dependency in all concentration. The change of the biopolymer viscosity on the pH showed the highest value at the pH 7.0 and it showed lower at acidic condition than at alkaline condition comparatively.

• Macromolecular Research
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• v.16 no.6
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• pp.517-523
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• 2008

A RGD (Arg-Gly-Asp) conjugated chitosan hydrogel was used as a cell-supporting scaffold for articular cartilage regeneration. Thermosensitive chitosan-Pluronic (CP) has potential biomedical applications on account of its biocompatibility and injectability. A RGD-conjugated CP (RGD-CP) copolymer was prepared by coupling the carboxyl group in the peptide with the residual amine group in the CP copolymer. The chemical structure of RGD-CP was characterized by $^1H$ NMR and FT IR. The concentration of conjugated RGD was quantified by amino acid analysis (AAA) and rheology of the RGD-CP hydrogel was investigated. The amount of bound RGD was $0.135{\mu}g$ per 1 mg of CP copolymer. The viscoelastic parameters of RGD-CP hydrogel showed thermo-sensitivity and suitable mechanical strength at body temperature for cell scaffolds (a> 100 kPa storage modulus). The viability of the bovine chondrocyte and the amount of synthesized glycosaminoglycans (GAGs) on the RGD-CP hydrogels were evaluated together with the alginate hydrogels as a control over a 14 day period. Both results showed that the RGD-CP hydrogel was superior to the alginate hydrogel. These results show that conjugating RGD to CP hydro gels improves cell viability and proliferation, including extra cellular matrix (ECM) expression. Therefore, RGD conjugated CP hydrogels are quite suitable for a chondrocyte culture and have potential applications to the tissue engineering of articular cartilage tissue.

• Macromolecular Research
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• v.17 no.11
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• pp.863-869
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• 2009

The effect of a multiwalled carbon nanotube (MWCNT) dispersion on the electrical, morphological and rheological properties of polycarbonate (PC)/MWCNT composites was investigated, with and without pretreating the MWCNTs with hydrogen peroxide oxidation and lyophilization. The resulting PC/treated MWCNT composites showed higher electrical conductivity than the PC/untreated MWCNT composites. The morphological behavior indicated the treated composites to have greater dispersion of MWCNTs in the PC matrix. In addition, the electromagnetic interference shielding efficiency (EMI SE) of the treated composites was higher than that of the untreated ones. Rheological studies of the composites showed that the complex viscosity of the treated composites was higher than the untreated ones due to increased dispersion of the MWCNTs in the PC matrix, which is consistent with the electrical conductivity, EMI SE and morphological studies of the treated composites. The latter results suggested that the increased electrical conductivity and EMI SE of the treated composites were mainly due to the increased dispersion of MWCNTs in the PC matrix.

• Journal of Electrochemical Science and Technology
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• v.14 no.3
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• pp.262-271
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• 2023

For electrode stability and the electrochemical performance of the Li-ion cell, it is essential that the active ingredients and unique additives in the polymer binder be well dispersed with the solvent-based slurry. The efficient procedure used to create the slurry affects the rheological characteristics of the electrode slurry. When successively adding different steps of Nmethyl-2-pyrrolidone (NMP) solvent to the cathode composition, it is evenly disseminated. The electrochemical performance of the Li-ion cells and the electrodes made with slurry formed by single step and multiple steps of addition of NMP solvent are examined. To preform rheological properties of cathode electrode slurry on Ni-rich Lithium Nickel-Cobalt-Aluminum Oxide (LiNi_0.80Co_0.15Al_0.05) (NCA). Also, we investigate different step addition of electrode formation and mechanical strength characterization like peel strength. According to the EIS study, a multi-step electrode slurry has lower internal resistance than a single-step electrode slurry, which results in better electrical characteristics and efficiency. Further, microstructure of electrodes is obtained electrochemical performance in the 18650 cylindrical cells with targeted capacity of 1.5 Ah. The slurry of electrodes prepared by single step and multiple steps of addition of NMP solvent and its effect on the fabrication of 1.5 Ah cells. A three-step solvent addition on slurry has been found to be a lower internal resistance than a single-step electrode slurry as confirmed by the EIS analysis, yielding improved electrical properties and efficiency.

• Polymer(Korea)
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• v.33 no.5
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• pp.397-406
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• 2009

We have fabricated source-drain electrodes for OTFTs using a screen-printing technique with carbon-black pastes as conductive paste. And effects of dispersants contents (SOP 10-40%) on the dispersity of carbon-black pastes and characteristics of screen-printed source-drain electrodes for OTFTs using two types of dispersants (DB-2150, DB-9077) were investigated. As contents of both dispersants were increased the dispersity of carbon-black mill-bases was improved, whereas the carbon-black pastes exhibited different dispersion characteristics. For the case of DB-2150, the dispersity of the pastes was improved with increasing dispersant content and the storage modulus G' in their rheology characteristics were reduced. But, for the DB-9077, the storage modulus G' of pastes were increased with dispersant content due to the flocculated network structure formed by interactions among carbon-black powders and dispersants. But, since this flocculated network structure of the pastes using DB-9077 resulted in the conduction path of carbon-black structures, the conductivities of screen-printed electrodes and mobilities of the OTFTs with them were better than those using pastes with DB-2150.