• The Journal of Korean Academy of Prosthodontics
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• v.62 no.1
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• pp.20-27
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• 2024

As a high-performance polymer, Polyetherketoneketone (PEKK) has good biocompatibility and excellent physical properties and is used in several areas, including dentistry. Many successful cases of implant-supported fixed prostheses with a PEKK framework have been reported; however, a long-term observation of the reported cases and discussion of complications are not available. In this case report, we present three cases of implant-supported fixed prostheses with a PEKK framework veneered with composite resin, lithium disilicate crown, and high-impact polymethyl methacrylate (PMMA), and discuss their 6-year follow-up results.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.425-428
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• 2003

This study deals with the mechanical properties of polymethyl methacrylate(PMMA) mortars without crosslinking agent. Waste expanded polystyrene(EPS) is used as a multifunctional admixture such as a thickener, a extender, a shrinkage reducing agent, a assistant to polymerization. PMMA mortars are prepared with various EPS contents of binder and subjected to a dry and a dry/heat combined curing, and tested for working life, flexural and compressive strengths. From the test results, the working life of PMMA mortars without crosslinking agent is shortened with raising EPS content of binder. The flexural and compressive strengths of the PMMA Mortars are decreased somewhat with increase in the EPS content. PMMA mortars with good mechanical properties could be manufactured without any crosslinking agent and their properties would be controled by adjusting EPS content of binder.

• Advances in nano research
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• v.9 no.2
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• pp.83-90
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• 2020

This research investigates the effect of single walled carbon nanotubes (SWCNTs) dimensions in terms of diameter on the mechanical properties (longitudinal and transverse Young's modulus) of the simulated nanocomposites by molecular dynamics (MDs) method. MDs utilized to create nanocomposite models consisting of five case studies of SWCNTs with different chiralities (5, 0), (10, 0), (15, 0), (20, 0) and (25, 0) as the reinforcement and using polymethyl methacrylate (PMMA) as the common matrix. The results show that with increasing of SWCNTs diameter, the mechanical and physical properties increase. It is important that with the increasing of SWCNTs diameter, density, longitudinal and transverse Young's modulus, shear modulus, poisson's ratio, and bulk modulus of simulated nanocomposite from (5, 0) to (25, 0) approximately becomes 1.54, 3, 2, 1.43, 1.11 and 1.75 times more than (5, 0), respectively. Then to validate the results, the stiffness matrix is obtained by Materials studio software.

• Journal of the Korean Applied Science and Technology
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• v.20 no.4
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• pp.353-357
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• 2003

Sodium azide (SA) is commonly used as propellant for inflating automatic safety bags and other chemical manufacturing purposes. The investigation of potentially thermal hazard of sodium azide and its mixture with polymers are very important because it can occur an expected traffic accident so we took a experiment s using different scanning calorimeter (DSC) in nitrogen atmosphere. The decomposition temperature were about $350{\sim}450^{\circ}C$. We could find not only exothermic reaction was remarkably decreased in mixture s of acrylonitrile-butadiene-styrene (ABS) and polyvinyl chloride (PVC), but also increasing mixed rate of ABS, polyvinyl alcohol (PVA) and polymethyl methacrylate (PMMA) decreased thermal decomposition heat.

• Clinics in Shoulder and Elbow
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• v.23 no.3
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• pp.156-158
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• 2020

PHILOS plate fixation in osteoporotic proximal humerus fracture of old age is well-known for high complication rate, especially metal failure, providing various augmentation techniques, such as calcium phosphate cement, allogenous or autologous bone graft. We report a case of polymethyl methacrylate augmentation to provide appropriate reduction with a significant mechanical support. This can be a treatment option for displaced unstable osteoporotic proximal humerus fracture with marked bony defect.

• Laser Solutions
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• v.6 no.1
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• pp.33-40
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• 2003

The ablative decomposition mechanism of PMMA(polymethyl methacrylate) and PET(polyethylene terephthalate) with KrF excimer laser(λ : 248nm, pulse duration: 5㎱) is investigated. The UV/Vis spectrometer analysis showed that PMMA is a weak absorber and PET is a strong absorber at the wavelength of 248nm. The results(surface debris, melt, etch depth, etching shape) from drilling and direct writing experiments imply that ablation mechanism of PMMA is dominated by photothermal process, while that of PET is dominated by photochemical process.

• Journal of IKEEE
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• v.13 no.2
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• pp.126-131
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• 2009

To overcome short channel effects, wrap-around field effect transistors have drawn a great deal of attention for their superior electrostatic coupling between the channel and the surrounding gate electrode. In this paper, we introduce a bottom-up technique to fabricate a wrap-around field effect transistor using silicon nanowires as the conduction channel. Device fabrication was consisted mainly of electron-beam lithography, dielectrophoresis to accurately align the nanowires, and the formation of gate electrode using electrochemical deposition. The electrolyte for electrochemical deposition was made up of non-toxic organic-based solution and liquid nitrogen was used as a method of maintaining the shape of polymethyl methacrylate(PMMA) during the process of electrochemical deposition. Patterned PMMA can be used as a nano-template to produce wrap-around gate nano-structures.

• Korean Chemical Engineering Research
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• v.43 no.1
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• pp.47-52
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• 2005

The wide use of metal dusts have been found in industrial field and many dust explosion accidents occur by fire spread of dust layer. In this study, we developed a new experimental device to examine fire and explosion characteristics of the dust layer. Aspects of the burning zone over metals(Mg, Zr, Ta, Ti, etc) and PMMA(Polymethyl methacrylate) dust layers have been investigated experimentally to clarify behaviors (Spread rate and quenching distance) and effects of $N_2$ surrounding gas on the fire spread over metal dust layers. From the experimental result, it was found that the spread rate of metal dusts is larger than PMMA, the dependability of spread rate over the thickness of dust layer is small, and the minimum oxygen concentration of spread flame over Mg dust layer is 3.6-3.7 vol%. Since high correlation between the spread rate and the reciprocal of quenching distance was seen, relative risk prediction in those inflammable parameters can be predicted.

• Journal of Digital Convergence
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• v.18 no.4
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• pp.309-314
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• 2020

Polymethyl methacrylate (PMMA) is concerned with promoting oral infection due to its low antibacterial activity. To overcome this, the nanoparticles of Ag-MSN, nGO, and CNP were mixed with MMA liquid in a weight ratio of 0, 0.25, 0.5, 1.0, 2.0% compared to resin powder using Orthocryl from Dentarum, a calibration resin, and then instructed by the manufacturer. Accordingly, a specimen for calibration was prepared by mixing PMMA: MMA (1.2: 1) ratio, and physical properties of the calibration resin, antifungal experiments, and statistical analysis were performed. As a result of antibacterial experiments, the antibacterial properties of Ag-MSN increased. In nGO, the antibacterial adhesive effect increased hydrophilicity, not a change in surface roughness. The higher the CNP concentration, the higher the antibacterial activity. This suggests its potential usefulness as an antibacterial dental material for orthodontic devices and temporary restorations.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.332-335
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• 2004

Polymethyl Methacrylate(PMMA) mortars using EPS solution-based binders are prepared with various unsaturated polyester resin(UP) contents of binder, and tested for working life. heat exothorm temperature, length change. compressive strength and temperature dependence of compressive strength. As a result, the working life of PMMA mortar is lengthened with raising UP content of binder. Length change of the mortar was condensed from expansion to shrinkage with increasing UP content, and non shrinkage of the mortar is obtained at about UP content of $2.5\%$. The compressive strength of the mortar is increased with an increase in the UP content and reach maximum at UP content of $5\%$. However thermal resistance improvement of the mortar by increasing UP content was not recognized. UP resin was recommended as an effective agent for shrinkage control and strength development of PMMA mortar.