• Restorative Dentistry and Endodontics
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• v.28 no.3
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• pp.209-221
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• 2003

The objectiveness of this study was to evaluate whether low-viscosity composite can bond effectively to dentin surface without bonding resin. The low-viscosity composites being 50wt% filler content were made by the inclusion of bonding resin of two self-etching systems(Cleafil SE Bond, Unifil Bond) varied with contents as 0, 10, 20, 30, 40, 50wt%. Exposed dentin surfaces of extracted 3rd molars are used. Dentin bond strengths were measured. The tests were carried out with a micro-shear device placed testing machine at a CHS of 1mm/min after a low-viscosity composite was filled into an iris cut from micro tygon tubing with internal diameter approximately 0.8mm and height of 1.0mm. 1 Flexural strength and modulus was increased with the addition of bonding resin. 2. Micro-shear bond strength to dentin was improved according to content of bonding resin irrespective of applying or not bonding resin in bonding procedure, and that of Clearfil SE Bond groups was higher than Unifil Bond. 3. There were no significant difference whether use of each bonding resin in bonding procedure for S-40, S-50, U-50(p＞0.05). 4. In SEM examination, resin was well infiltrated into dentin after primed with self-etching primer only for S-50 and U-50 in spite of the formation of thinner hybrid layer. Low viscosity composite including some functional monomer may be used as dentin bonding resin without an intermediary bonding agent. It makes a simplified bonding procedure and foresees the possibility of self-adhesive restorative material.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.55-63
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• 2012

This paper presents materials and processing technique to manufacture low viscous strain-hardening cementitious composite which is suitable for structures requiring low viscosity of materials. The micromechanics and fracture mechanics tools coupled with processing techniques were adopted to achieve low viscosity of composites as well as high tensile strain capacity. Optimal volume and length of fibers and interfacial properties between fibers and matrix for composites with tensile strength of 2~3MPa were determined on the basis of the micromechanical analysis and the steady-state cracking theory. Then six mixtures were determined and the experiment was carried out to evaluate the viscosity and uniaxial tensile performance of those. From the test results, it is verified that the strain-hardening cementitious composite with low viscosity suitable for grouting applications in fresh state as well as high ductility over 1.5% in hardened state can be feasible.

• Journal of the Korean Ceramic Society
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• v.49 no.6
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• pp.542-548
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• 2012

The viscosity of a ceramic slurry depends on the slurry concentration, particle shape and size, hydrodynamic interactions, temperature, shear rate, pre-treatment condition and the method of measurement with the selected equipment. Representative ceramic slurries with low to high viscosity levels are selected from colloidal silica, barium titanate slurry and glass frit paste. Rotational rheometers and vibrational viscometers are used to compare the measured viscosity for various ceramic slurries. The rotational rheometer measured the viscosity according to the change of the shear rate or the rotational speed. On the other hand, the vibrational viscometer measured one point of the viscosity in a fixed vibrational mode. The rotational rheometer allows the measurement of the viscosity of a ceramic paste with a viscosity higher than 100,000 cP, while the vibrational viscometer provides an easy and quick method to measure the viscosity without deformation of the ceramic slurry due to the measurement method. It is necessary to select suitable equipment with which to measure the viscosity depending on the purpose of the measurement.

• Proceedings of the KACD Conference
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• 2001.11a
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• pp.558.1-558
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• 2001

Flowable resin composite is a relatively new restorative material. It has been reported that a low viscosity, low modulus intermediate resin applied between the bonding agent and restorative resin act as an "elastic buffer" that can relieve contraction stress. This in-vitro study aimed to evaluate the effect of flowable composite resin as a restorative material on regional tensile bond stredgth to cervical wedge shaped cavity walls. (omitted)

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.378-378
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• 2009

The ionic liquid-based sulfonated hydrocarbon composite membranes was prepared for use in anhydrous high temperature-polymer electrolyte fuel cells (HT-PEFCs). Ionic liquid behaves like water in the composite membranes under anhydrous condition. However the composite membranes show a low conductivity and high gas permeability as the content of ionic liquid increases due to its high viscosity and content of ionic liquid, respectively. Hence, in order to enhance the proton conductivity and to reduce the gas permeability of the composite membranes with low content of ionic liquids, the acid containing a common ion of ionic liquid was added to the composite membranes. The characterization of composite membranes was carried out using small-angle X-ray scattering (SAXS), thermogravimetric analyzer (TGA) and impedance spectroscopy. As a result, the composite membranes containing acid showed higher proton conductivity than those with no acid under the un-humidified condition due to a decrease in viscosity. In addition, the proton conductivity of composite membranes increased with increasing mole concentration of acid.

• Polymer(Korea)
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• v.31 no.6
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• pp.491-496
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• 2007

In the polymeric dental restorative composites, the resin matrix mainly contains 70 wt% 2,2-bis[4-(2-hydroxy-3-methacryloyloxy propoxy) phenyl] propane (Bis-GMA), as a base resin and 30 wt% triethylene glycol dimethacrylate (TEGDMA) as a diluent. Even though the viscosity of the resin matrix is rapidly decreased by adding TEGDMA, addition of TEGDMA to the Bis-GMA results in reduction in the mechanical properties and increase in the curing shrinkage of the dental composite. In order to fabricate dental composite exhibiting excellent properties by reducing TEGDMA content in the resin matrix, in this study, Bis-GMA derivatives, which do not contain hydroxyl groups, were used instead of Bis-GMA. The curing characteristics of Bis-GMA derivatives were similar with those of Bis-GMA, while the former exhibited lower viscosity and water absorption than the latter. Comparing the curing shrinkage of the dental composite containing Bis-GMA derivative with that prepared from Bis-GMA, the reduction in curing shrinkage was about 25%. Dental composites prepared from new resin matrices also exhibited low water uptake and better properties in mechanical strength.

• Journal of the Korean Ceramic Society
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• v.34 no.10
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• pp.1037-1044
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• 1997

Mechanical properties and water stability of HAC/PVA based MDF cement composite were investigated using polyurethane(PU) resin, silane coupling agent and various PVA. The results were as follows ; The flexural strength of MDF cement composite increased as increasing with PVA content. Low-viscosity PVA developed higher flexural strength than high-viscosity PVA under a drying curing condition. But the strength of water immersed specimen decreased. Water stability of MDF cement improved as increasing with content of PU. Consequently, water stability of polyurethane 7% added MDF cement was about 2 times higher than that of the controlled specimen. Furthermore, the strength and water stability of diamine group based silane couling agent in using MDF cement increased and improved dramatically.

• Applied Chemistry for Engineering
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• v.28 no.5
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• pp.559-564
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• 2017

In this study, the optimization process was carried out by using the central composite model of the response surface methodology in waste cooking oil based biodiesel production process. The acid value, reaction time, reaction temperature, methanol/oil molar ratio, and catalyst amount were selected process variables. The response was evaluated by measuring the FAME content (more than 96.5%) and kinematic viscosity (1.9~5.5 cSt). Through basic experiments, the range of optimum operation variables for the central composite model, such as reaction time, reaction temperature and methanol/oil molar ratio, were set as between 45 and 60 min, between 50 and $60^{\circ}C$, and between 8 and 12, respectively. The optimum operation variables, such as biodiesel production reaction time, temperature, and methanol/oil molar ratio deduced from the central composite model were 55.2 min, $57.5^{\circ}C$, and 10, respectively. With those conditions the results deduced from modeling were as followings: the predicted FAME content of the biodiesel and the kinematic viscosity of 97.5% and 2.40 cSt, respectively. We obtained experimental results with deduced operating variables mentioned above as followings: the FAME content and kinematic viscosity of 97.7% and 2.41 cSt, respectively. Error rates for the FAME content and kinematic viscosity were 0.23 and 0.29%, respectively. Therefore, the low error rate could be obtained when the central composite model among surface reaction methods was applied to the optimized production process of waste cooking oil raw material biodiesel.

• Nano
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• v.13 no.12
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• pp.1850137.1-1850137.9
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• 2018

A series of silica surface-capped with hexamethyldisilazane (denoted as $H-SiO_2$) were prepared by liquid-phase in-situ surface-modification method. The as-obtained $H-SiO_2$ was incorporated into acrylic amino (AA) baking paint to obtain AA/$H-SiO_2$ composite extinction paints and/or coatings. $N_2$ adsorption-desorption tests were conducted to determine the specific surface area as well as pore size and pore volume of $H-SiO_2$. Moreover, the effects of $H-SiO_2$ matting agents on the physical properties of AA paint as well as the gloss and transmittance of AA-based composite extinction coatings were investigated. Results show that $H-SiO_2$ matting agents possess a large specific surface area and pore volume than previously reported silica obtained by liquid-phase method. Besides, they have better dispersibility in AA baking paint than the unmodified silica. Particularly, $H-SiO_2$ with a silica particle size of $6.7{\mu}m$ and the dosage of 4% (mass fraction) provides an extinction rate of 95.2% and a transmittance of 79.3% for the AA-based composite extinction coating, showing advantages over OK520, a conventional silica matting agent. Along with the increase in the silica particle size, $H-SiO_2$ matting agents cause a certain degree of increase in the viscosity of AA paint as well as a noticeable decrease in the gloss of the AA-based composite extinction coating, but they have insignificant effects on the hardness and adhesion to substrate of the AA-based composite coatings. This means that $H-SiO_2$ matting agents could be well applicable to preparing low-viscosity and low-gloss AA-based matte coatings.

• Advanced Composite Materials
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• v.17 no.3
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• pp.191-214
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• 2008

Polypropylene/layered silicate nanocomposites containing maleic anhydride grafted polypropylene were prepared by melt compounding and their rheological behavior was investigated in shear flow. Transient and steady shear flows were simulated numerically by using the K-BKZ integral constitutive equation along with experimentally determined damping functions under dynamic oscillatory and step strain shear flows. Nonlinear shear responses were predicted with the K-BKZ constitutive equation using two different damping functions such as the Wagner and PSM models. It was observed that PP-g-MAH compatibilized PP/layered silicate nanocomposites have stronger and earlier shear thinning and higher steady shear viscosity than pure PP resin or uncompatibilized nanocomposites at low shear rate regions. Strong damping behavior of the PP/layered silicate nanocomposite was predicted under large step shear strain and considered as a result of the strain-induced orientation of the organoclay in the shear flow. Steady shear viscosity of the pure PP and uncompatibilized nanocomposite predicted by the K-BKZ model was in good agreement with the experimental results at all shear rate regions. However, the model was inadequate to predict the steady shear viscosity of PP-g-MAH compatibilized nanocomposites quantitatively because the K-BKZ model overestimates strain-softening damping behavior for PP/layered silicate nanocomposites.