• Journal of the Korean Society of Safety
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• v.19 no.2
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• pp.47-53
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• 2004

Emulsion polymerization ws carried out using Alkyl methacrylate(RMA) like MMA, EMA, BMA and Styrene Monomer(SM) for core-shell latex preparation. It was synthesized at $80^{\circ}C$ in the presence of anionic surfactant SLS(Sodium Lauryl Sulfate). FT-IR and DSC analysis are used to confirm the synthesized core-shell emulsion latexes. Moreover DSC and TGA were used to investigate the thermal characterisitcs of them. The differences of the decomposition rate and the activation energy from TGA and DSC analysis are not so big. It considers that the pendent group is not affect of the thermal characteristics and stability on core-shell latexes, which is synthesized with RMA and Styrene. For investigating combustion products, LC50 values were calculated by FED(Fractional Effective Dose)from the Pyrolyzer-Mass sepctrometer.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.1
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• pp.71-84
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• 1992

Polymer-Impregnated Concrete(PIC) is a composite material of concrete and polymer. PIC has superior properties compared to conventional cement concrete, such as strength, stiffness, toughness, durability, water-proofing, chemical resistance. However, the usage of PIC has been limited to repairing materials and non-structural applications due to the lack of the design criteria and the analytical model to determine structural behavior. The objective of this study is experimentally to develop the optimum mixing proportions of polymer impregnants and the stress-strain responses, the strength characteristics, the fatigue and creep behaviors, and the durabilities of MMA(methyl methacrylate)-based PIC.

• Current Photovoltaic Research
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• v.4 no.4
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• pp.140-144
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• 2016

In this paper, core-shell structure of nickel/gold (Ni/Au) conductive layer on poly-methyl-methacrylate (PMMA) micro-ball was fabricated and its conduction property was investigated. Firstly, PMMA micro-ball was synthesized by using dispersion polymerization method. Size of the ball was $2.8{\mu}m$ within ${\pm}7%$ deviation, and appropriate elastic deformation of the PMMA micro-ball ranging from 31 to 39% was achieved under 3 kg pressure. Also, 200 nm thick Ni/Au conductive layer was fabricated on the PMMA micro-ball by uniformly depositing with electroless-plating. Adhesion of the conductive layer was optimized with help of surface pre-treatment, and the layer adhered without peeling-off despite of thermal expansion by collision with accelerated electrons. Composite paste containing core-shell structured particles well cured at low temperature of $130^{\circ}C$ while pressing the test chip onto the substrate to make electrical contact, and electrical resistance of the conductive layer showed stable behavior of about $6.0{\Omega}$. Thus, it was known that core-shell structured particle of the Ni/Au conductive layer on PMMA micro-ball was feasible to flexible electronics.

• Advances in nano research
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• v.15 no.6
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• pp.551-565
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• 2023

Coupled porous curved beams, due to their low weight and high flexibility, have many applications in engineering. This study investigates the vibration behavior of coupled porous curved beams in different boundary conditions. The system consists of two curved beams connected by a mid-layer of elastic springs. These beams are made of various materials, such as homogenous steel foam, and composite materials with PMMA (polymethyl methacrylate) and SWCNT (single-walled carbon nanotube) used as the matrix and nanofillers, respectively. To obtain equivalent material properties, the role of mixture (RoM) was employed, followed by the implementation of the porosity function. The system's governing equations were obtained by employing FSDT and Hamilton's law. To investigate thermal vibration, temperature was implemented as a load in the governing equations. The GDQ method was used to solve these equations. To demonstrate the applicability of the GDQ method in calculating the frequencies of the system and the correctness of the developed program, a validation study was conducted. After validation, numerous examples were presented to investigate the behavior of single and coupled curved beams in various material properties and boundary conditions. The results indicate that the frequencies of the curved beams and the system depend highly on the amount of porosity (n) and the distribution pattern. The system frequencies decreased with an increase in the porosity coefficient. The stiffness of the springs had no effect on the first mode frequency but increased frequencies of other modes in a specific range. The frequencies of the system decreased with an increase in environmental temperature.

• Membrane Journal
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• v.18 no.2
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• pp.116-123
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• 2008

Proton conductive hybrid nanocomposite polymer electrolyte membranes comprising polystyrene-5-poly (hydroxyethyl methacrylate) (PS-b-PHEMA), sulfosuccinic acid (SA) and phosphotungstic acid (PWA) were prepared by varying PWA concentrations. The PHEMA block was thermally crosslinked by SA via the esterification reaction between -OH of PHEMA and -COOH of SA. Upon the incorporation of PWA into the diblock copolymer, the symmetric stretching bands of the $SO_3^-$ group at $1187cm^{-1}$ shifted to a lower wavenumber at $1158cm^{-1}$, demonstrating that the PWA particles strongly interact with the sulfonic acid groups of SA. When the concentration of PWA was increased to 30wt%, the proton conductivity of the composite membrane at room temperature increased from 0.045 to 0.062 S/cm, presumably due to the intrinsic conductivity of the PWA particles and the enhanced acidity of the sulfonic acid in the membranes. The membrane containing 30wt% of PWA exhibited a proton conductivity of 0.126 S/cm at $100^{\circ}C$. Thermal stability of the composite membranes was also enhanced by introducing PWA nanoparticles.

• Restorative Dentistry and Endodontics
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• v.24 no.1
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• pp.88-99
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• 1999

The purpose of this study was to investigate the physical properties of experimental composite resins made with the spherical and crushed fillers. The 14 experimental composite resins containing 0, 5, 10, 15, 20 and 25%(w/w) in spherical filler group and 0, 10, 20, 30, 40, 50, 60 and 70%(w/w) in crushed filler group, incorporated in a Bis-GMA matrix (Aldrich Co., USA), were made with 1% ${\gamma}$-methoxy silane treated fillers. The polymer matrix was made by dissolving 0.7%(w/w) of benzoyl peroxide(Janssen Chemical Co. Japan) in methacrylate monomer, whereupon 0.7%(v/v) N,N-dimethyl-p-toluidine(Tokyo Kasei Co. Japan) was added to the monomer. The weight percentage of each specific particle size distribution could be determined from a knowledge of the specific gravity, the weight(w/w), and corresponding volume %(v/v) of the filler sample in resin monomer. In crushed silica group and spherical silica group, the diametral tensile strengths and compressive strengths were measured with Instron Testing Machine(No.4467), and analyzed in 14 experimental composite resins made by filler fractions. The shear bond strength of 14 experimental composite resins to bovine enamel was measured with universal testing machine(Instron No.4467). The fracture surfaces were sputter-coated with a gold film and investigated by SEM. The results were as follows; 1. The diametral tensile strength was tendency to increase in crushed silica group, but not in spherical silica group. The highest diametral tensile strength was found in 20% filler fractions of two groups. 2. The compressive strength was higher in 15%(w/w) and 20%(w/w) in spherical silica group than in crushed silica group, but not in spherical silica group. 3. The significant correlation was noticed in increase in shear bond strength in crushed silica group, but not in spherical silica group. 4. The significantly highest shear bond strength was noticed in 50% filler concentration in crushed silica group, and in 15% filler concentration in spherical silica group, it was not significant in relation. 5. In crushed silica group, cut surface of resin matrix and the interface between resin and filler is obvious. In spherical silica group, fractures that occurred through the filler particles were round in shape.

• Magazine of the Korea Concrete Institute
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• v.6 no.2
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• pp.97-107
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• 1994

The objective of this study is to develop polymer-impregnated concrete(PIC), which is a newly developed composite material made by impregnating polymer impregnanls into hardened normal concrete, and to develop analytical techniques for its proper applications. Crystalline methyl methacrylate(MMA) is chosen as a monomer of polymer impregnants. The corrlpositions of polymer impregnants and producing processes are developed by analyzing the effects of penetration, polymerization, thermal safety, and strengthening characteristics. On t he basis of experimental results of this study, various strength characteristics and stress strain constitutive relations are formulated in terms of the compressive strength of normal concrete and the polymer loadings, which can be applied for analysis and design of PIC members. In order to provide a model for fracture analysis of flexural members, fracture toughness, fracture energy, critical crack width, and tension softening relations near crack tip are also formulated in terms of member depth, initial notch depth, and the flexural strength of normal concrete. The structural analysis procedure and the finite element computer program developed in the study are applicable to evaluate elastic behavior, ultimate strength, and tension softening behavior of MMA type PIC structural members subject to various loading conditions. The accuracy and effectiveness of the developed computer program is examined by comparing the anal ytical results with the experimental results. Therefore, it is concluded that the developed structural analysis procedure and the finite element computer program are applicable to analysis and design of in-situ and precast PIC structural members.

• Polymer(Korea)
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• v.30 no.5
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• pp.385-390
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• 2006

In this work, the effect of carbon nanofiber (CNF) on thermal properties, and friction and wear behavior of CNF/PMMA composites were examined. While thermal properties of the composites were investigated with differential scanning calorimetry, thermograyimetric analyzer, and dynamic mechanical analyzer friction and wear behaviors were examined using a friction and wear tester. The glass transition temperature (Tg), integral procedural decomposition temperature (IPDT), storage modulus (E'), and tan ${\delta}$ appeared at higher temperatures with increasing CNF content, which were probably attributed to the presence of strong interactions between the carbonaceous fillers and the PMMA resins matrix. The wear loss in the composites decreased at 0.1 wt% CNF and then increased with 5-10 wt% CNF content. This was due to the existence of large aspect ratio CNF in PMMA which led to an alignment of PMMA chains and an increase of mechanical interlocking, resulting in the formation of crosslinked structures between CNF and PMMA in the composite.

• Polymer(Korea)
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• v.36 no.4
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• pp.525-530
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• 2012

In this study, silane-crosslinked organic/inorganic composite membranes were prepared by simultaneous irradiation grafting of binary monomer mixtures (styrene and 3-(trimethoxysilyl)propyl methacrylate (TMSPM)) with various compositions onto a poly(ethylene-alt-tetraethylene) (ETFE) film and followed by sol-gel processing and sulfonation to provide a silane-crosslinked structure and a proton conducting ability, respectively. The Fourier transform infrared spectroscopy (FTIR) and thermo gravimetric analysis (TGA) were utilized to confirm the crosslinking of ETFE-g-PS/PTMSPM films. The prepared membranes with similar ion exchange capacity but a different TMSPM content were selected and their membrane properties were compared. The ETFE-g-PSSA/PTMSPM membranes were characterized by water uptake, dimensional stability, and proton conductivity after sulfonation. The membrane electrode assemblies (MEA) of the prepared membranes were fabricated and their single cell performances were measured.

• Composites Research
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• v.30 no.4
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• pp.247-253
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• 2017

In this study, the mechanical behavior and interface properties of boron nitride nanotube-poly(methyl methacrylate) nanocomposites are predicted using the molecular dynamics simulations and the double inclusion model. After modeling nanocomposite unit cell embedding single-walled nanotube and polymer, the stiffness matrix is determined from uniaxial tension and shear tests. Through the orientation average of the transversely isotropic stiffness matrix, the effective isotropic elastic constants of randomly dispersed microstructure of nanocomposites. Compared with the double inclusion model solution with a perfect interfacial condition, it is found that the interface between boron nitride nanotube and polymer matrix is weak in nature. To characterize the interphase surrounding the nanotube, the two step domain decomposition method incorporating a linear spring model at the interface is adopted. As a result, various combinations of the interfacial compliance and the interphase elastic constants are successfully determined from an inverse analysis.