• Korean Journal of Materials Research
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• v.27 no.4
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• pp.199-205
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• 2017

In this study, (3,4-epoxycyclohexane)methyl 3,4-epoxycyclohexylcarboxylate acrylate was synthesized by reacting (3,4-epoxycyclohexane)methyl 3,4-epoxycyclohexylcarboxylate with acrylic acid to minimize hardening shrinkage and to improve heat resistance, which are known as disadvantages of photopolymers for 3D printing application. Urethane acrylate was synthesized by reacting 1,3,5-triazine-2,4,6-triamino alcohol, 2-hexylethyl acrylate, and isophorone diisocyanate in order to improve the mechanical properties without deteriorating the heat resistance. The physical properties before and after the synthesis of the acrylate and the mechanical properties when the urethane acrylate was applied were investigated. The reaction progress of the composite was examined by FTIR and $^{13}C$ NMR. The heat deflection temperature, flexural strength, and surface hardness of the molding were measured. The curing behavior by Photo-DSC ultraviolet irradiation was also examined.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.6
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• pp.139-147
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• 2022

In this study, we designed a high-strength, low-alkali type cement composite for artificial reef by mixing various binders and evaluated whether it is possible to manufacture it with an ME method 3D printer. As a result of the tests, it is found that it is important to control the water-binder ratio, the silica sand-binder ratio, and the type of silica sand in order to control the fluidity of the cement composites to enable 3D printing. The surface quality of 3D printer output can be achieved by adjusting the amount of viscosity agent added while obtaining printable fluidity. In the cement composites mixing proportion using the alpha-type hemihydrate gypsum, a setting control agent needs to be used to control the quick setting effect. It is also necessary to derive the time to maintain the fluidity, and to apply it when printing. To obtain the required strength, the mix proportion needs to be modified while satisfying the fluidity level of 3D-printable cement composites. In the present study, 3D-printable mix proportions were designed by the use of multi-component binders including alpha-type hemihydrate gypsum a for low-alkali type artificial reefs, and the printability was confirmed. A further study needs to be performed to quantitatively evaluate the alkali reduction effect.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.40-41
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• 2006

In this work, we developed the 0-3 type piezoelectric composite to incorporate the advantages of both ceramic and polymer. The PVDF-PZT composites were fabricated with various mixing ratio by 3-roll mi11 mixer. The composite solutions were coated on ITO bottom-electrode deposited on PET (polyethylene terephthalate) polymer film by the conventional screen-printing method. After depositing the top-electrode of silver-paste, 4kV/mm of DC field was applied at $120^{\circ}C$ for 30min to poling the 0-3 composite film. The value of $d_{33}$ was increased as the PZT weight percent was increases. But the $g_{33}$ value showed the maximum at 65 wt% of PZT powder.

• Conservation Science in Museum
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• v.31
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• pp.39-54
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• 2024

We wanted to check The feasibility of substituting the manual ceramic packaging technology with 3D digital technology using cotton pad packaging material was examined. To examine the shock absorption, vibration resistance and compression resistance of 3D packaging material printed out by using TPU material, composite vibration, and packaging compression and drop tests were conducted. As the results of the tests, the 3D packaging material displayed vibration resistance that has been improved by approximately 10~20% based on the damping ratio of the composite vibration test, compression resistance performances that are more than 5 times higher, and shock absorption performance was also improved as the packaged object was not broken in the six-sided drop test. Based on these results, it is determined that it would be possible to secure the reusability of the ceramic packaging materials and simplify packaging techniques, and to present diversity in the packaging materials and packaging technologies.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.5
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• pp.20-29
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• 2022

In this study, in order to improve the durability of the cement composite printed with the ME type 3D printer, PDMS, sodium silicate, and a surface hardener were employed. Post-treatment was performed on 3D-printed cement composite by coating after immersion, and the degree of improvement in durability was evaluated. As a result, in all evaluations, the durability performances of the post-processed specimens were improved compared to those of the plain specimens. Water absorption resistance, chloride penetration resistance, and carbonation resistance of the PDMS treated specimens were improved by 36.3 %, 77.1 %, and 50.4 % when compared to plain specimens. Freeze-thaw resistance of the specimens treated with sodium silicate was found to be the most excellent, with an average enhancement of 47.5% compared to plain specimens. It was found that PDMS was the most efficient post-treatment materials for 3D-printed cement composite. However, as suggested in this study, the post-treatment method by coating after immersion may not be applicable to cement composite structures printed with a 3D printer in field. Therefore, a follow-up study needs to be preformed on the durability enhancing materials suitable for 3D printing.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.6
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• pp.193-198
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• 2021

In this study, the rheological characteristics and of 3D printing composite materials and the compressive strength characteristics according to the lamination patterns were evaluated. As a result of rheology test, rapid material change was observed after 60 minutes of extrusion, yielding stress 1.4 times higher than immediately after mixing, and plastic viscosity was 14.94-25.62% lower. The compressive strength of the specimens manufactured in the mold and the laminated specimens were compared, and the lamination pattern of the laminated specimens were 0°, 45°, and 90° as variables. The compressive strength of the mold casting specimen and the laminated specimen from 1 to 28 days of age showed similar performance regardless of the lamination pattern. In particular, at the age of 28 days, the modulus of elasticity, maximum compressive strength, and strain at maximum stress of all specimens were almost the same. In order to analyze the interface of the laminated specimens, X-ray CT analysis of the specimen whose compressive strength were measured was performed. Through CT analysis, it was confirmed that cracks did not occur at the lamination interface, which can be judged that the interface in the laminated specimen behaved in an integrated manner.

• Journal of Sensor Science and Technology
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• v.32 no.5
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• pp.290-294
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• 2023

Among various types of harmful gases, hydrogen sulfide is a strong toxic gas that is mainly generated during spillage and wastewater treatment at industrial sites. Hydrogen sulfide can irritate the conjunctiva even at low concentrations of less than 10 ppm, cause coughing, paralysis of smell and respiratory failure at a concentration of 100 ppm, and coma and permanent brain loss at concentrations above 1000 ppm. Therefore, rapid detection of hydrogen sulfide among harmful gases is extremely important for our safety, health, and comfortable living environment. Most hydrogen sulfide gas sensors that have been reported are electrical resistive metal oxide-based semiconductor gas sensors that are easy to manufacture and mass-produce and have the advantage of high sensitivity; however, they have low gas selectivity. In contrast, the electrochemical sensor measures the concentration of hydrogen sulfide using an electrochemical reaction between hydrogen sulfide, an electrode, and an electrolyte. Electrochemical sensors have various advantages, including sensitivity, selectivity, fast response time, and the ability to measure room temperature. However, most electrochemical hydrogen sulfide gas sensors depend on imports. Although domestic technologies and products exist, more research is required on their long-term stability and reliability. Therefore, this study includes the processes from electrode material synthesis to sensor fabrication and characteristic evaluation, and introduces the sensor structure design and material selection to improve the sensitivity and selectivity of the sensor. A sensor case was fabricated using a 3D printer, and an Ag reference electrode, and a Pt counter electrode were deposited and applied to a Polytetrafluoroethylene (PTFE) filter using PVD. The working electrode was also deposited on a PTFE filter using vacuum filtration, and an electrochemical hydrogen sulfide gas sensor capable of measuring concentrations as low as 0.6 ppm was developed.

• Korean Journal of Radiology
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• v.22 no.5
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• pp.706-713
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• 2021

Objective: To evaluate the impact of surgical simulation training using a three-dimensional (3D)-printed model of tetralogy of Fallot (TOF) on surgical skill development. Materials and Methods: A life-size congenital heart disease model was printed using a Stratasys Object500 Connex2 printer from preoperative electrocardiography-gated CT scans of a 6-month-old patient with TOF with complex pulmonary stenosis. Eleven cardiothoracic surgeons independently evaluated the suitability of four 3D-printed models using composite Tango 27, 40, 50, and 60 in terms of palpation, resistance, extensibility, gap, cut-through ability, and reusability of. Among these, Tango 27 was selected as the final model. Six attendees (two junior cardiothoracic surgery residents, two senior residents, and two clinical fellows) independently performed simulation surgeries three times each. Surgical proficiency was evaluated by an experienced cardiothoracic surgeon on a 1-10 scale for each of the 10 surgical procedures. The times required for each surgical procedure were also measured. Results: In the simulation surgeries, six surgeons required a median of 34.4 (range 32.5-43.5) and 21.4 (17.9-192.7) minutes to apply the ventricular septal defect (VSD) and right ventricular outflow tract (RVOT) patches, respectively, on their first simulation surgery. These times had significantly reduced to 17.3 (16.2-29.5) and 13.6 (10.3-30.0) minutes, respectively, in the third simulation surgery (p = 0.03 and p = 0.01, respectively). The decreases in the median patch appliance time among the six surgeons were 16.2 (range 13.6-17.7) and 8.0 (1.8-170.3) minutes for the VSD and RVOT patches, respectively. Summing the scores for the 10 procedures showed that the attendees scored an average of 28.58 ± 7.89 points on the first simulation surgery and improved their average score to 67.33 ± 15.10 on the third simulation surgery (p = 0.008). Conclusion: Inexperienced cardiothoracic surgeons improved their performance in terms of surgical proficiency and operation time during the experience of three simulation surgeries using a 3D-printed TOF model using Tango 27 composite.

• Elastomers and Composites
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• v.57 no.3
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• pp.81-91
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• 2022

Composites based on engineering thermoplastics exhibit excellent mechanical and thermal properties and simple processing and reprocessing attributes, and are widely used in the aerospace, three-dimensional (3D) printing, and automobile industries. Polyphenylene sulfide (PPS) is one of the most desirable engineering thermoplastics, owing to its superior thermal performance, inherent flame retardancy resulting from the presence of sulfur in its backbone structure, chemical resistance, and satisfactory electrical properties. However, pure PPS resin has limited applicability owing to its brittleness. To compensate for these shortcomings, various filler materials are frequently used in the manufacture of PPS composites. In this review, we would like to present the correlation between the structure and physical properties of PPS composite materials using various fillers.

• Journal of Integrative Natural Science
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• v.17 no.2
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• pp.53-58
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• 2024

This study explores the enhancement of mechanical properties in Polymethyl Methacrylate (PMMA) composites through the incorporation of Methyl Methacrylate (MMA) and Ethylene Glycol Dimethacrylate (EGDMA). Utilizing Digital Light Processing (DLP) technology, we conducted a series of experiments to analyze the impact of varying concentrations of MMA and EGDMA on PMMA. The results indicate that while MMA demonstrates non-linear and variable mechanical strength across different PMMA concentrations, EGDMA consistently improves mechanical strength as PMMA concentration increases. This consistent enhancement by EGDMA suggests a stable and predictable reinforcement effect, which is critical for applications requiring high mechanical strength. Our comparative analysis highlights that EGDMA is a more effective additive than MMA for optimizing the mechanical performance of PMMA composites. Specifically, EGDMA's ability to provide uniform reinforcement across various PMMA concentrations makes it ideal for high-strength applications. These findings are significant for material scientists and engineers focused on the design and development of advanced PMMA-based materials. In conclusion, this research underscores the importance of selecting appropriate additives to enhance the mechanical properties of PMMA composites. The superior performance of EGDMA in reinforcing PMMA suggests its potential for broader applications in fields such as automotive, construction, medical devices, and 3D printing. This study provides valuable insights that can guide future research and development in high-performance composite materials, paving the way for innovative applications and improved material efficiency.