• The Korean Journal of Rheology
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• v.10 no.4
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• pp.227-233
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• 1998

The effects of 1 mol% N-benzylpyrazinium hexafluoroantimonate(BPH) as a thermal latent initiator and blend compositions composed of cycloaliphatic and DGEBA epoxies were investigated in the rheological properties and cure kinetics. Latent properties were performed by measurement of the conversion as a function of reaction time using isothermal DSC at $150^{\circ}C$ and $50^{\circ}C$ Rheological properties of the blend systems were investigated in terms of isothermal experiments using a rheometer. The gelation time was obtained from the evaluation of storage modulus (G'), loss modulus (G") and damping factor (tan$\delta$)). Cross-linking activation energy ($E_c$) was also determined from the Arrhenius equation based on gel time and curing temperature. As a result, the gel time and cross-linking activation energy increased with increasing DGEBA composition. The cure activation energies ($E_a$) were obtained by Kissinger method using dynamic DSC thermograms. In this work, the cure activation energy decreased with increasing CAE concentration, which might be resulted from the short repeat units, simple side-groups and viscosity of reaction media.edia.

• Proceedings of the Korean Fiber Society Conference
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• 2003.04a
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• pp.195-197
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• 2003

Polymer layered silicate nanocomposite has become an important area of polymer research becaues of its predominant properties in mechanical and thermal properties. Polymer layered silicate nanocomposites show outstanding improvements in tensile strength and modulus, heat distortion temperature, gas and liquid permeability, solvent resistance, and so on. But These improved properties are realized only when silicate particles are well dispersed in polymer matrix. (omitted)

• Proceedings of the Korean Society of Rheology Conference
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• 2003.05a
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• pp.21-24
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• 2003

No Abstract, See Full Text

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.679-684
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• 2011

Branched polypropylenes (LCB-PP) with a long chain branch were prepared by the solid-state and molt-state reaction. Divinylbenzene (DVB), 1,4-benzenediol (RES), and furfuryl sulphide (FS) were used as branching agents of fabricate LCB-PP/silicate composites. Chemical structures, thermal properties, and rheological properties of the LCB-PP were determined by FT-IR, DSC, TGA, and dynamic rheometer (ARES). The chemical structure of the LCB-PP was confirmed by the existence of =C-H stretching peak of the branching agent at $3100cm^{-1}$. From DSC and TGA results, the melting reaction was more effective than the solid state reaction in the manufacture of LCB-PP, which was additionally certified by rheological properties. Based on rheological properties, FS was the best for branching efficiency of PP. Compared to PP, LCB-PPs indicated an increase of complex viscosity in the low frequency and shear thinning tendency, and G'-G" plot represented an increase in elasticity and the heterogeneousness in a melt state. Rheological properties of LCB-PP/silicate composites were observed with the silicate content. When 5 wt% silicate was added in LCB-PP, distinct changes in the shear thinning and the slope of G'-G" plots were observed.

• Composites Research
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• v.27 no.3
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• pp.115-121
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• 2014

The effect of addition of gypsum on the rheology, physico-mechanical properties, thermal properties and morphology development of polymer composites based on polyvinyl chloride (PVC) and waste-gypsum with and without methylene-butadiene-styrene (MBS) has been studied. It was shown that the replacement of gypsum for methylene-butadiene-styrene (MBS) component in PVC/gypsum polymer composites enhanced the tensile strength and stiffness of composites, but gradually decreased its impact strength. The observation of morphology, the results of the physico-mechanical properties and thermal properties proved simultaneously that PVC/gypsum composite with the waste-gypsum content of 22.56 wt% reached the optimum results among five kinds of PVC/gypsum polymer composite materials investigated.

• Polymer(Korea)
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• v.32 no.2
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• pp.116-124
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• 2008

A commercialized biobased and biodegradable poly(lactic acid)(PLA) containing the functional monomer of glycidyl methacrylate (GMA) was chemically modified using reactive extrusion to enhance its melt strength. Modified PLAs were prepared with various contents of GMA and initiator, and were characterized by observing their gel fraction, thermal properties, melt viscoelasticity and biodegradability. The complex viscosity and storage modulus of chemically modified PLA with the initiator alone was increased by addition of initiator and were more increased in the presence of GMA. There was a optimum content of GMA showing the maximum complex viscosity with the amount of initiator. The biodegradebility of modified PLA was slightly decreased by addition of GMA.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1404-1409
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• 2007

Polymers for laser sintering were needed in order to fabricate the articles with the three-dimensional duplication equipment of SLS (selective laser sintering) process. The thermal properties, particle size, distribution, and shape of polymer powder had a close relation with the processibility of laser sintering. In this study, we prepared new polymer powders with uniform size and higher bulk density by wet process. Wet process consists of several finely-controlled steps such as dissolution, nucleation, propagation and crystallization. Several additives were added to improve the thermal, rheological, and flow properties.

• Applied Biological Chemistry
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• v.38 no.4
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• pp.353-358
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• 1995

The influence of dry-heat treatment($130{\sim}220^{\circ}C$) on the gelatinization and rheological properties of corn starch(11.4% moisture) was examined. The enthalpy of gelatinization measured by differential scanning calorimetry decreased above $190^{\circ}C$. The viscosity of starch by alkali gelatinization increased as the heating temperature rised. All the values including peak viscosity on amylograms and shear stress, apparent viscosity, consistency index and yield stress of thermal-gelatinized starch dispersion showed decreasing tendencies with increasing of heating temperature from above $170^{\circ}C$ compared with those of raw starch. The apparent viscosity and yield stress of all the samples thermal-gelatinized at $90^{\circ}C$ were increased considerably with process of gelatinization time and especially their rapid increase at the early stage was observed in the $190^{\circ}C$ sample. But all the rheological parameters of $220^{\circ}C$ sample recorded very low values compared with those of the others.

• Korean Journal of Food Science and Technology
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• v.26 no.2
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• pp.103-109
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• 1994

Changes in the rheological properties and the linear viscoelasticity of fish protein gel upon the thermal processing were studied by using mathematical models with stress-relaxation data. The linear viscoelasticity of surimi gel was observed in the range of the true strain $0.105{\sim}0.693$ and cross-head speed $50{\sim}250\;mm/min$ applied in this study. The results of the generalized Maxwell analysis showed that the magnitudes of elastic elements $(E,\;E_e)$ were increased, but the viscous element $({\eta}) $was decreased, as the cross-head speeds and strain levels were increased. Compared to the protein gel heated directly at $90^{\circ}C$ without preheating, the protein gel pretreated at $4^{\circ}C$ and $40^{\circ}C$ showed the higher elastic modulus, but showed different trends in the viscous component, depending on the rheological model applied. Thus, the approaching methods and curve fitting of two mathematical models of stress-relaxation to describe the viscoelastic properties of fish protein gel were discussed.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.1
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• pp.8-16
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• 2017

Structural integrity of solid rocket depends on the residual reactions between constituents of its composition(post cure, migration etc.), the oxygen(or anti-oxydent) in the free volume and humidity (desiccant) under the perfect sealed condition. Mechanical Properties of composite solid propellant arising from those factors are very complex. Moreover the propulsion are faced with thermal loads from diurnal & seasonal cycle till firing. In this study, the fast evaluation method of long term mechanical properties is suggested based on Thermo-Rheological Simplicity from curing oven to cool-down stage in view point of thermal stabilization. For this subject, endurance tester having temperature control capability are devised. From the results from incremental load and strain, non-linear characteristics are discussed.