• Membrane Journal
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• v.31 no.6
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• pp.434-442
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• 2021

Poly(vinylidene fluoride) (PVDF) membrane has a good membrane durability because of its high mechanical resistance, thermal and chemical stability. However, the strong hydrophobic property of PVDF membrane can induce a low water permeability and easy fouling by proteins and organic matters. In order to improve the anti-fouling properties of PVDF membrane, the PVDF mixed matrix asymmetric membranes impregnated with biofunctional material 𝛽-cyclodextrin (𝛽-CD) in the membrane structure were prepared by phase inversion method. The membrane filtration experiments of pure water and BSA solution were performed using the PVDF/𝛽-CD mixed matrix asymmetric membranes prepared according to the 𝛽-CD contents. The experiments showed that the introduction of 𝛽-CD into the PVDF polymer matrix contributed to increase in the hydrophilic property of the PVDF membranes, and this led to the reduction of contact angles and improvement of anti-fouling properties. The PVDF/𝛽-CD membrane which was prepared using the dope solution with a 2 wt% 𝛽-CD content represented 64 L/m²·h of pure water flux, 95% of BSA rejection and maximum 80% of flux enhancements compared to flux results of the pristine PVDF membrane.

• Applied Chemistry for Engineering
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• v.33 no.3
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• pp.296-301
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• 2022

Due to the fact that zirconium based metal-organic frameworks (Zr-MOFs), such as UiO-66, have a large specific surface area and excellent selective adsorption capacity, Zr-MOFs are gaining attention as materials that can provide protection from the attack of chemical warfare agents in battleground. However, most of the metal-organic frameworks have an issue of selective adsorption capacity degraded by water molecules when exposed to the atmosphere, because of the weak metal-organic ligand bonds and the presence of voids. Therefore, polydimethylsiloxane (PDMS), a representative hydrophobic polymer material, was coated on the surface of UiO-66 to enhance the sustainability of the diisopropyl methylphosphonate (DIMP) sorption capacity in the battleground condition. Through the analysis of surface structure and organic functional group distribution of PDMS coated UiO-66, silicon was confirmed to be evenly coated. The contact angle increased by over 30° for the PDMS coated UiO-66, indicating that the hydrophobicity was improved. In addition, both the UiO-66 and PDMS coated UiO-66 were used as adsorbents for DIMP, a similar chemical warfare agent, to investigate the durability of adsorption capacity in a high humidity environment. The PDMS coated UiO-66 showed higher durability of adsorption capacity for 20 days than that of pristine UiO-66.

• 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.

• Composites Research
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• v.35 no.5
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• pp.347-358
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• 2022

Carbon fiber is an excellent structural material, which has been proven in many industries, and the shipbuilding industry is no exception. In particular, in advanced maritime countries, special ships of the Navy and Coast Guard with carbon fiber composite hulls have already been deployed. In Korea, carbon fiber composite materials have been applied to a 10-ton class leisure craft or a 30-ton class patrol, but no research has been done on a hundred of tons or more vessels. In this study, the feasibility study of a 500-ton patrol vessel with a carbon fiber composite hull was conducted through an analysis of similar cases abroad. As a result, it was recognized that the developed hull can be reduced in weight by about 21% to 25% compared to the existing aluminum or FRP hull. It was also confirmed that this light-weight effect can induce the improvement of the maximum speed and the improvement of the operating range via simulations.

• Journal of the Korean Electrochemical Society
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• v.25 no.3
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• pp.105-112
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• 2022

For the commercialization of all-solid-state batteries, it is essential to develop a solid electrolyte that can be operable at room temperature, and it is necessary to manufacture all-solid-state batteries by adopting materials with high ionic conductivity. Therefore, in order to increase the ionic conductivity of the existing oxide-based solid, Li₇La₃Zr₂O₁₂ (LLZO) doped with heterogeneous elements was used as a filler material (Al and Nb-LLZO). An electrolyte with garnet-type inorganic filler doped was prepared. The binary metal element and the polymer mixture of poly(ethylene oxide)/poly(propylene carbonate) (PEO/PPC) (1:1) are uniformly manufactured at a ratio of 1:2.4, The electrochemical performance was tested at room temperature and 60 ℃ to verify room temperature operability of the all-solid-state battery. The prepared composite electrolyte shows improved ionic conductivity derived from co-doping of the binary elements, and the PPC helps to improve the ionic conductivity, thereby increasing the capacity of all-solid-state batteries at room temperature as well as 60 ℃. It was confirmed that the capacity retention rate was improved.

• Journal of Adhesion and Interface
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• v.24 no.1
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• pp.26-35
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• 2023

Generally, solvent-type coatings generate a large amount of volatile organic chemicals(VOC), which are carcinogenic substances, in the manufacturing process, and their use is regulated due to environmental problems. There is also the problem of resource depletion due to limited fossil fuels. Therefore, in this study, UV-curable urethane acrylate oligomers were synthesized with different contents of isosorbide, which is a biomass material, and proceeded to evaluate the physical properties of coatings. As the isosorbide contents increased, the viscosity, glass transition temperature, tensile strength, stain resistance, and pencil hardness increased, but elongation and flexibility decreased, and BOI-3 showed the best adhesion. The isosorbide content of the oligomer fixed at 20%, UV-curable urethane acrylate oligomer was synthesized according to the content ratio of polycaprolactone diol(PCL) and Ecoprol H1000(Ecoprol). As the PCL/Ecoprol content ratio increased, the glass transition temperature, elongation, and flexibility increased, but the tensile strength and pencil hardness decreased. It was confirmed that the adhesion and stain resistance increased by improving the surface bonding strength of PCL. All films of oligomers synthesized were transparent without discoloration.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.29 no.1
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• pp.15-25
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• 2023

Since the COVID-19 crisis, the use of disposable packaging materials and delivery services, which raise environmental and social issues with waste disposal, has significantly increased. Antimicrobial active packaging has emerged as a viable solution for extending the shelf-life of foods by minimizing microbial growth and decomposition. In this review article, we provide a comprehensive overview of current research trends in antimicrobial active film and coating published over the last five years. First, we introduced various polymer materials such as film and coating that are used in active packaging. Next, various types of antimicrobial (antibacterial, antifungal, and antiviral) packaging including essential oil, extracts, biological material, metal, and nanoparticles were introduced and their activities and mechanisms were discussed. Finally, the current challenges and prospects were discussed. Overall, this review provides insights into the recent advancements in antimicrobial active packaging research and highlights the potential of the technology to enhance food safety and quality.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.4
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• pp.9-14
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• 2022

Silica aerogel is a porous material with a very low density and high specific surface area. Still, its application is limited due to its weak mechanical properties due to structural features. To solve this problem, a method of complexing it with various polymers has been proposed. We synthesized polyimide cross-linked silica aerogel by the sol-gel process to obtain high mechanical properties. Tetraethyl orthosilicate (TEOS) was used as a precursor to make silica aerogel, and 3- aminopropyltriethoxysilane (APTES) was used as a coupling agent for cross-linking polyimide. Polyimide was synthesized using pyromellitic dianhydride and 3,5-diaminobenzoic acid, and mechanical properties were improved by crosslinking polyimide with 10 repeating units in the polyimide chain using the reaction formula ${\frac{n_1}{n_2}}={\frac{n}{n+1}}$ To realize silica aerogel, polyimide having various weight ratios was added before gelation, resulting in a 19-fold or greater increase in maximum compressive strength compared to pure silica aerogel. From this study, an enhancement of silica aerogel could be enhanced through polymer cross-linking bonds.

• Industry Promotion Research
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• v.9 no.1
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• pp.31-38
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• 2024

In this study, evaluated the properties of layered silicate-based nanocomposite sensitive film. For the fabrication of nanocomposite materials, we selected organically modified layered silicate materials, specifically Cloisite^® and Bentone^®, which were treated with quaternary ammonium salts. The impedance of the humidity sensors containing organically modified montmorillonite/hectorite clay decreased with increasing relative humidity(RH%). In the case of the Cloisite^® humidity sensor exhibited slightly better impedance linearity and hysteresis compared to the Bentone^® 38 humidity sensor. Additionally the impedance of the sensor with Bentone^® 38 addition was the lowest when compared to the Cloisite^®-modified sensor. Comparing the Cloisite^®-modified sensors individually, we observed different moisture absorption characteristics based on the hydrophilic properties of the organic-treated materials. The response speed of Cloisite^® 93A tended to be slower due to differences in moisture evaporation rates influenced by the hydrophilic organic components. Based on these results, moisture barriers utilizing organically modified layered silicate materials may exhibit slightly lower moisture absorption properties compared to conventional polymer-based moisture barriers. However, their excellent stability, simple processing, and cost-effectiveness make them suitable for humidity sensor applications.

• Clean Technology
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• v.30 no.1
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• pp.1-12
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• 2024

Nanoplastics (NP) exhibit distinct material properties compared to microplastics (MP), necessitating their separate recognition. Review of research outcomes and policy documents on NP reveals that most policy frameworks predominantly define MPs as solid synthetic polymer materials measuring 5 mm or less, but do not distinguish them from NP. However, recent revisions in regulations by the EU classify NPs as particles that range in size from 1 to 1,000 nm, as confirmed by some academic studies. Research on NPs often relies on experimental investigations centered around water systems, with a focus on high-concentration experimental conditions using spherical polystyrene-based NPs in behavior and impact studies. Notably, the environmental behavior characteristics of NP show differences in influence depending on the NP type, emphasizing the need for field simulation research. These challenges are mirrored in Korean society, so it is necessary to redefine NP to be distinct from MP in both research and policy. This study aimed to assess the current state of NP management globally and domestically and highlight policy considerations and issues in the existing response to NP. Upon comprehensive review, it becomes apparent that reaching an international agreement on MP faces methodological limitations, which could potentially burden efforts to precisely define NP size. Therefore, referencing the EU's recent regulatory revisions is crucial in domestic policy. Specific adjustments should commence from the MP concept through insights from the domestic industry, guidance from the academic community, and thorough discussions to ensure social acceptance.