• Korea-Australia Rheology Journal
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• v.13 no.4
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• pp.189-196
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• 2001

The phase morphology is an important factor in the rheology of immiscible polymer blends. Through its size and shape, the interface between the two phases determines how the components and the interface itself will contribute to the global stresses. Rheological measurements have been used successfully in the past to probe the morphological changes in model blends, particularly for dilute systems. For more concentrated blends only a limited amount of systematic rheological data is available. Here, viscosities and first normal stress differences are presented for a system with nearly Newtonian components, the whole concentration range is covered. The constituent polymers are PDMS and PIB, their viscosity ratio can be changed by varying the temperature. The data reported here have been obtained at 287 K where the viscosities of the two components are identical. By means of relaxation experiments the measured stresses are decomposed into component and interfacial contributions. The concentration dependence is quite different for the two types of contribution. Except for the component contributions to the shear stresses there is no clear indication of the phase inversion. Plotting either the interfacial shear or normal stresses as a function of composition produces in some cases two maxima. The relaxation times of these stresses display a similar concentration dependence. Although the components have the same viscosity, the stress-component curves are not symmetrical with respect to the 50/50 blend. A slight elasticity of one of the components seems to be the cause of this effect. The data for the more concentrated blends at higher shear rates are associated with a fibrillar morphology.

• Polymer(Korea)
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• v.26 no.1
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• pp.145-151
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• 2002

Thermoplastic starch(TPS) was prepared from mixing starch and glycerol by twin extruder. The blends were then prepared from high density polyethylene(HDPE) and TPS. Mechanical properties, thermal properties, and morphology of the blends were investigated. Their biodegradability was also studied by using aerobic composting method(ISO14855). Tensile strength, modulus and elongation at break decreased as the content of TPS increased. In particular elongation at break decreased rapidly even at the lower content of TPS. The melting temperatures of the blends were not changed, which showed that HDPE and TPS were immiscible. The morphology of the fractured surface of blend films was investigated by scanning electron microscopy(SEM). It was found that phases were separated. After composting for 45days, the biodegradability of the blends increased as the content of TPS increased.

• Polymer(Korea)
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• v.35 no.6
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• pp.580-585
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• 2011

This article aims to enhance the biodegradability and environment-friendliness of petroleum based biodegradable poly(butylene adipate-co-succinate-co-terephthalate)(PBAST) by blending chemically modified thermoplastic starch(CMPS). CMPS is a kind of bio-based biodegradable resin which is manufactured by reacting starch with maleic anhydride(MA) in the presence of a plasticizer and a free radical initiator. The characteristic properties of PBAST/CMPS blends were investigated by observing their morphology, thermal, mechanical properties, and biodegradability. The good interfacial adhesion between the phases examined by SEM revealed that PBAST/CMPS blends were compatible blends. The tensile strength and elongation decreased with increasing CMPS content, while modulus increased. The biodegradability of the blends was much higher than that of pristine PBAST and increased with increasing CMPS contents.

• Bulletin of the Korean Chemical Society
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• v.16 no.9
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• pp.873-885
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• 1995

The local structural and thermodynamical properties of blends A-B/H of a diblock copolymer A-B and a homopolymer H are studied using the polymer reference interaction site model (RISM) integral equation theory with the mean-spherical approximation closure. The random phase approximation (RPA)-like static scattering function is derived and the interaction parameter is obtained to investigate the phase transition behaviors in A-B/H blends effectively. The dependences of the microscopic interaction parameter and the macrophase-microphase separation on temperature, molecular weight, block composition and segment size ratio of the diblock copolymer, density, and concentration of the added homopolymer, are investigated numerically within the framework of Gaussian chain statistics. The numerical calculations of site-site interchain pair correlation functions are performed to see the local structures for the model blends. The calculated phase diagrams for A-B/H blends from the polymer RISM theory are compared with results by the RPA model and transmission electron microscopy (TEM). Our extended formal version shows the different feature from RPA in the microscopic phase separation behavior, but shows the consistency with TEM qualitatively. Scaling relationships of scattering peak, interaction parameter, and temperature at the microphase separation are obtained for the molecular weight of diblock copolymer. They are compared with the recent data by small-angle neutron scattering measurements.

• Elastomers and Composites
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• v.40 no.2
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• pp.128-135
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• 2005

Optimal conditions for preparation of starch/PVA blends were investigated with the consideration of factors that may influence mechanical properties of the blends. $L_{27}(3^{13})$ experimental designs based on Taguchi method were performed and then tensile strength, strain at break, Young's modulus and tear strength of films of the blends were measured to determine the optimal conditions for preparation. Interaction effects for each factor were determined from analysis of variables. Results of $L_{27}(3^{13})$ experiments indicated that glycerol and urea were important process factors affecting optimization of the mechanical properties.

• Korea-Australia Rheology Journal
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• v.17 no.2
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• pp.71-77
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• 2005

We investigated thermal, rheological, morphological and mechanical properties of a binary blend of poly(lactic acid) (PLA) and poly(butylene succinate adipate) (PBSA). The blends were extruded and their molded properties were examined. DSC thermograms of blends indicated that the thermal properties of PLA did not change noticeably with the amount of PBSA, but thermogravimetric analysis showed that thermal stability of the blends was lower than that of pure PLA and PBSA. Immiscibility was checked with thermal data. The rheological properties of the blends changed remarkably with composition. The tensile strength and modulus of blends decreased with PBSA content. Interestingly, however, the impact strength of PLA/PBSA (80/20) blend was seriously increased higher than the rule of mixture. Morphology of the blends showed a typical sea and island structure of immiscible blend. The effect of the blend composition on the biodegradation was also investigated. In the early stage of the degradation test, the highest rate was observed for the blend containing $80wt\%$ PBSA.

• Rubber Technology
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• v.7 no.1
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• pp.8-16
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• 2006

Plastic/rubber blends are ultrasonically treated during continuous extrusion in order to investigate the in-situ compatibilization of the blends without any chemicals. The mechanical properties of each blend were significantly improved by ultrasonic treatment. It is believed that ultrasonic treatment of the blends enhances intermolecular interaction, improves adhesion at the interface and creates copolymers during very short time. The created copolymers are believed to be a major reason for enhancing mechanical properties of the blends by in-situ compatibilization during extrusion. This process can be applied fur preparing plastic/rubber blends to make thermoplastic elastomers or plastic/plastic and rubber/rubber blends, and for making novel copolymers from practically any pairs of existing polymers to achieve desirable chemical and physical properties.

• Polymer(Korea)
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• v.27 no.4
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• pp.285-292
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• 2003

The compatibility of poly(lactic acid)/poly($\varepsilon$-caprolactone) (PLA/PCL) blends as a function of blend composition was studied and triphenyl phosphite (TPP) was applied to PLA/PCL blends as a reactive compatibilizer. Especially the effect of compatibility on the crystallization behavior in both PLA/PCL blends and PLA/PCL blends with TPP was considered. PLA/PCL blends were immiscible based on thermal characteristics of PLA/PCL blends and the miscibility was depend upon the blend composition. The enhancement of compatibility was found in PLA/PCL blends with TPP depend upon its content. The rate of crystallization in PLA/PCL blend varied with blend composition. This was understood as the development of nucleation at the interface of PLA-PCL due to the immiscibility. TPP was acting as a compatibilizer as well as an agent for the acceleration of spherulite growth In PLA. As a result, the crystallization rate increased and the size of spherulite became larger than that of PLA/PCL blend without TPP.

• Polymer(Korea)
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• v.29 no.2
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• pp.166-171
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• 2005

EPDM (ethylene propylene diene monomer)/silicone rubber blends were prepared and the influence of a compatibilizer and thermal aging on the properties of the blends was investigated. The blends of which the compositions were varied in the range of 90/10 through $10/90\;wt\%$ were melt mixed by using a Brabender Plasticoder (internal mixer) and were vulcanized by a hot press. The morphology of the vulcanized EPDM/SR blends was examined by scanning electron microscopy (SEM). After the thermal Aging for 24, 48, 96 hrs at $100^{\circ}C$ in an air oven, hardness, tensile strength, elongation and contact angle of the blends were investigated. From the result of the morphology, it was confirmed that the domain size of the blends containing the compatibilizer was reduced. As the increase of the thermal aging time, hardness and tensile strength of the blends decreased but elongation and contact angle increased.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.374-374
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• 2006

Poly (N-isopropylacrylamide) (PNIPAAm) shows a lower critical solution temperature (LCST) at $32^{\circ}C$. Consequently, its thermosensitivity has extensively been investigated in coating materials as well as biomedical and agricultural industry. However, mechanical properties of the swollen gels are generally poor and reinforcement is often desired. A series of interpenetrating polymer networks (IPNs) and emulsion blends hydrogels of polyurethane (PU) and PNIPAAm were prepared in order to overcome the shortcomings of a normal PNIPAAm hydrogels. Regarding the mechanical reinforcement of swollen gel, a significant increase in compression and tensile properties has been obtained by incorporating PU.