• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1509-1514
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• 2008

To fabricate microsized poly(methyl methacrylate)(PMMA) beads of uniform size and density on poly(ethylene terephthalate) (PET) fis, we introduce an electro spraying technique that uses a target electrode applied with an ac electric fid. Using the apparatus and various material properties, we could obtain uniform size PMMA beads which were deposited on the thin PET film. The optical properties, transmittance and light diffusivity of the fis electro sprayed with the PMMA were characterized. The results show that the sprayed beads appear to act as a good optical diffuser, like microlenses. To understand the effect of process variables, applied field conditions and rheological properties, the morphological pictures of the deposited particles were investigated through the optical and scanning electron microscope.

• 한국재료학회지
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• 제14권8호
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• pp.587-594
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• 2004

Three-dimensionally ordered macroporous (3DOM) structures of the $LiCoO_2$ electrode materials for Li secondary batteries were fabricated by using the close-packed arrays of PMMA spheres served as templates. In order to successfully fabricate the cathode materials with highly ordered array form, the metal citrates were applied to new precursors. The precursor/template composites were prepared by the infiltration with metal citrate precursors into the voids of template. By removing the PMMA templates, then, the inverse opal structures with the uniform pores of narrow size distribution were resulted. It was confirmed that the 3DOM $LiCoO_2$ material is to take a single phase of rocksalt (R3m) structure. In addition, 3DOM $LiNiO_2$ and $LiMn_{2}O_4$ cathode materials were fabricated using an identical preparation procedure. Also, the morphology of the 3DOM cathode materials calcined at $500^{\circ}C\;to\;700^{\circ}C$ was observed by scanning electron microscope.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.655-656
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• 2005

In the future, plastic based system will play a crucial role in modem life, for examples, transparent display or disposable electronics and so on. In this paper, we introduced a new method to fabricate the metal line on the plastic substrate. Metal lines were fabricated by hot embossing and CMP process on PMMA (polymethylmethacrylate) substrates. A Si mold was made by wet etching process and a PMMA wafer was cut off from I mm thick PMMA sheet. A 100 nm thick Al was deposited on PMMA wafers. The Al deposited PMMA wafer and the Si mold carefully sandwiched which was directly imprinted by hot embossing. After imprinting process, a residual Al layer was removed by CMP process. Finally, we found the entire process may be very useful to fabricate the metal line on plastic substrates.

• 대한치과기공학회지
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• 제41권3호
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• pp.203-209
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• 2019

Purpose: The purpose of this study was to investigate the mechanical properties of polymer prosthetic and restorative materials for dental CAD/CAM using two test method; surface characteristics and shear bond strength. Methods: Commercialized CAD/CAM polymer blanks were investigated; One kinds of PMMA, and one PEKK blanks. A total of 20 PMMA and PEKK specimens were prepared, and each group was divided into 10 specimens. Average surface roughness was observed under surface profilometer. The contact angle was measured with a surface electrooptics. The bond strength was evaluated by a universal testing machine at a crosshead speed of 5mm/min. The data were statistically analyzed using independent t-test and Fisher's exact test(P<0.05). Results: The PMMA and PEKK group showed a significant difference in the shear bond strength with the composite resin(P<0.05). The surface roughness of the PEKK group was higher than that of the PMMA group. The fracture mode were observed in PEKK groups with 50% showing adhesive remnant index score. Conclusion: PEEK is used as substructure material and composite veneering material is applied. PEKK resins will contribute to the development of successful products that will provide structural and aesthetic satisfaction.

• Composites Research
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• 제30권5호
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• pp.288-296
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• 2017

본 연구에서는 전자기기 사용에 이슈가 되고 있는 발열 문제를 해결하고자 상변화물질(PCM)의 잠열 특성을 이용하여 폴리메틸메타크릴레이트(PMMA) 복합필름을 제조하고 방열 성능을 평가하였다. 이를 위해 용융온도가 서로 다른 두 가지의 상변화물질을 사용하여 제작한 PCM/PMMA 복합필름의 열적 특성을 비교 분석하여 다양한 사용조건에 따른 유효성을 검증하였고, Compression Molding 방법과 PCM Paste Sealing 방법에 따른 PCM/PMMA 복합필름의 방열 특성을 비교 분석하여 최대의 방열 효과를 달성할 수 있는 최적의 방법을 도출하였다. 또한 PCM/PMMA 복합필름의 방열 성능을 최대화하기 위해 열전도율이 높은 흑연과 그래핀을 추가로 적층하여 제조한 Hybrid 복합필름의 열적 특성을 분석하였고, 이들을 통해 향상된 방열 성능을 실험적으로 검증하였다. 본 연구를 통해 개발된 방열 성능이 우수한 복합필름은 다양한 전자기기에 활용되어 발열 문제를 효과적으로 해결할 수 있을 것으로 기대된다.

• Macromolecular Research
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• 제13권2호
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• pp.120-127
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• 2005

Conventional poly(methyl methacrylate) (PMMA) bone cement has been widely used as an useful biopolymeric material to fix bone using artificial prostheses. However, many patients had to be reoperated, due to the poor mechanical and thermal properties of conventional PMMA bone cement, which are derived from the presence of unreacted MMA liquid, the shrinkage and bubble formation that occur during the curing process of the bone cement, and the high curing temperature ($above 100^{\circ}C$) which has to be used. In the present study, a composite PMMA bone cement was prepared by impregnating conventional PMMA bone cement with ultra high molecular weight polyethylene (UHMWPE) powder, in order to improve its mechanical and thermal properties. The UHMWPE powder has poor adhesion with other biopolymeric materials due to the inertness of the powder surface. Therefore, the surface of the UHMWPE powder was modified with two kinds of silane coupling agent containing amino groups (3-amino propyltriethoxysilane ($TSL 8331^{R}$) and N-(2-aminoethyl)-3-(amino propyltrimethoxysilane) ($TSL 8340^{R}$)), in order to improve its bonding strength with the conventional PMMA bone cement. The tensile strengths of the composite PMMA bone cements containing $3 wt\%$ of the UHMWPE powder surface-modified with various ratios of $TSL 8331^{R}$ and $TSL 8340^{R}$ were similar or a little higher than that of the conventional PMMA bone cement. However, no significant difference in the tensile strengths between the conventional PMMA bone cement and the composite PMMA bone cements could be found. However, the curing temperatures of the composite PMMA bone cements were significantly decreased.

• Journal of Mechanical Science and Technology
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• 제15권7호
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• pp.1041-1050
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• 2001

Control of bone cement volume (PMMA) may be critical for preventing complications in vertebroplasty, the percutaneous injection of PMMA into vertebra. The purpose of this study was to predict the optimal volume of PMMA injection based on CT images. For this, correlation between PMMA volume and textural features of CT images was examined before and after surgery to evaluate the appropriate PMMA amount. The gray level run length analysis was used to determine the textural features of the trabecular bone. Extimation of PMMA volume was done using 3D visualization with semi-automatic segmentation on postoperative CT images. Then, finite element (FE) models were constructed based on the CT image data of patients and PMMA volume. Appropriate material properties for the trabecular bone were assigned by converting BMD to elastic modulus. Structural reinforcement due to the changes in PMMA volume and BMD was assessed in terms of axial displacement of the superior endplate. A strong correlation was found between the injected PMMA volume and the area of the intertrabecular space and that of trabecular bone calculated from the CT images (r=0.90 and -0.90, respectively). FE results suggested that vertebroplasty could effectively reinforce the osteoporotic vertebra regardless of BMD or PMMA volume. Effectiveness of additional PMMA injection tended to decrease. For patients with BMD well lower than 50mg/ml, injection of up to 30% volume of the vertebral body is recommended. However, less than 30% is recommended otherwise to avoid any complications from excessive PMMA because the strength has already reached the normal level.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.395-400
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• 2001

The Split Hopkinson Pressure Bar(SHPB) technique, a special experimental apparatus, has been used to obtain the material behavior under high strain rate loading condition. In this paper, dynamic deformation behaviors of the PMMA under high strain rate tensile loading are determined using SHPB technique.

• 한국정밀공학회지
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• 제33권10호
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• pp.865-873
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• 2016

The aim of this study was to examine the validity of fracture criterion for PMMA plates that have a V-notch with an end hole. The predicted stress intensity factors and crack initiation angles by the fracture criterion based on the maximum circumferential stress and the novozhilov's criteria were compared with the experimental results. By increasing the radius of end hole, the differences of predicted stress intensity factors and experimental results increased, possibly due to the plastic zone size. The results indicated that when the radius of end hole is < 1 mm, the fracture criterion would be useful.

• 한국정밀공학회지
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• 제28권12호
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• pp.1403-1410
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• 2011

Creep characteristic is an important failure mechanism when evaluating engineering materials that are soft material as polymers or used as mechanical elements at high temperatures. One of the popular thermo-elastic polymers, Polymethyl methacrylate(PMMA) which is used broadly for engineering polymer, as it has excellent mechanical and thermal properties compared to other polymers, was studied for creep characteristic at various level of stresses and temperatures. From the experimental results, the creep limit of PMMA at room temperature is 85 % of tensile strength. which is higher than that of PE (75%)at room temperature. Also the creep limits decreased to nil linearly as the temperatures increased, up to $120^{\circ}C$ of the melting point($267^{\circ}C$). Also the first and third stage among the three creep stages were non-existent nor were there any rupture failure which occurred for many metals at high temperatures.