• Journal of the Korean Applied Science and Technology
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• v.18 no.2
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• pp.153-159
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• 2001

Due to its low density, good mechanical properties and chemical inertness, glassy carbon(GC) has been studied for appications in several fields. A raw thermosetting resin of furanic resin was polymerized with a curing agent of p-toluenesulfonic acid monohydrate. The maximum yield of GC was obtained at the curing agent content of 1.0 wt% in furanic resin. In order to make thick GC, the affect of graphite filler addition to the furanic resin was investigated. The density and electrical resitivity of GC after graphitization were 1.45 $g/cm^{3}$ and 47 ${\times}10^{-4}$ ${\Omega}$ ${\cdot}$ cm respectively and the amorphous structure of GC was confirmed by XRD profiles with very broad peaks comparable to those of graphite at $206^{\circ}$ and $45^{\circ}$.

• Elastomers and Composites
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• v.53 no.3
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• pp.150-157
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• 2018

Fatigue properties of rubber are one of the most important characteristics in the rubber industry. In this study, the fatigue properties of MREs (magneto-rheological elastomers) based on NR (natural rubber), EPDM (ethylene-propylene diene monomer), and AEM (ethylene/acrylic elastomer) were investigated. For comparison, MREs with a Shore hardness of 60A were prepared. According to the relative results, the fatigue properties of EPDM MRE were the worst. Thus, we investigated methods to improve the fatigue properties of EPDM MRE by varying the carbon black content and curing systems of EPDM as the matrix of the MRE. Dynamic properties were measured using a fatigue tester and an RPA (rubber process analyzer), and the XPS (X-ray photoelectron spectroscopy) was used to analyze the curing system of the EPDM matrix. According to the results, the Payne effect increased and the fatigue resistance decreased as the carbon black content increased. In case of the curing system, the CV (conventional vulcanization) system was superior to the EV (efficient vulcanization) system in terms of the fatigue resistance. This was because the number of flexible bonds in the case of the CV system was higher than that in the case of the EV system. However, the EV system showed excellent mechanical properties because it had many monosulfidic bonds with strong binding energy.

• Elastomers and Composites
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• v.58 no.3
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• pp.142-151
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• 2023

In this study, we investigate the thermal and mechanical properties of composites comprising ethylene propylene diene monomer (EPDM) and polybutadiene (PB) obtained using carbon black (CB) as a reinforcing and compatibilizing filler. Owing to the significance of elastomeric materials in various industrial applications, blending of EPDM and PB has emerged as a strategic method to optimize the material properties for specific applications. This study offers insights into the blend composition, its microstructure, and the resulting macroscopic behaviors, focusing on the synergetic effects of composite materials. Furthermore, this study delves into curing and rheological behaviors, crosslink densities, and mechanical, thermal, and elastic properties of the elastomeric composites. Through systematic exploration, we believe that this study will be beneficial to material scientists and engineers working on developing advanced elastomeric composites.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.12
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• pp.87-97
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• 2020

In this study, a UV-cured GFRP molding is made using a combination of hand lay-up and resin transfer molding, and its properties are analyzed. The molded plates produced using various vacuum pressures (0 mmHg, -450 mmHg, and -760 mmHg) are examined via a comparison of hand lay-up molding and resin transfer molding. Tests are conducted by processing tensile specimens (ASTM D-5083), flexural test specimens (ASTM D-790), and ILSS test specimens (ASTM D-2344) according to each ASTM standard with a molded plate. Similarly, the UV-cured GFRP molding is compared against GFRP using epoxy. It was confirmed that the mechanical strengths of all the specimens increased when the vacuum pressure was increased and when UV curing was applied. This is believed to be because as the vacuum pressure increases, the pores of the cured specimen are removed, thereby reducing defects, and the bonding force between the glass fiber and the resin is stronger than that of the epoxy resin. It is expected that if resin transfer molding methods and UV-cured resins are used for molding GFRP composites in industry, products with better mechanical properties and faster curing time will be produced.

• Composites Research
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• v.33 no.6
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• pp.329-335
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• 2020

In this study, the thermo-rheological behaivors of petroleum pitches with different softening points were studied, and a B-stage phenolic resins/petroleum pitches blends were prepared by adding petroleum pitches to the phenolic resins. As a result, the petroleum pitch with different softening points decreased the fluidity of the petroleum pitch as the Quinoline insoluble (QI) content increased and showed the viscous properties of the solid. In addition, the effect of adding petroleum pitches having different softening points on the thermo-rheological properties of phenolic resins was investigated. When petroleum pitch with a high softening point was added, the fluidity of the phenolic resin was reduced, and the hardening behavior was fast. It was possible to control the curing rate and curing behavior of the phenolic resin by adding petroleum pitches of different softening points. Among them, the phenolic resin mixture to which P-Pitch 2 was added has a higher fluidity than other blends under the same curing temperature condition.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.6
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• pp.88-95
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• 2020

Currently, Fiber-Reinforced Plastic (FRP) composite materials are used in many industrial fields, owing to their superior stiffness and specific strength compared to metals. However, there are issues with FRP inefficiency, due to low productivity of such materials, environmental problems they pose and long curing times needed. Trying to address these issues, research was conducted towards the development of a FRP composite material with excellent properties and short production time, introducing a curing method using a UV lamp. Four types of composite materials were prepared, cured with catalyst or UV (CZ: Catalyst + ZNT 6345, CR: Catalyst + RF 1001 MV, UVZ: Photoinitiator + ZNT 6345, and UVR: Photoinitiator + RF 1001 MV). Examination of the chemical and mechanical properties of these composites showed that UV-cured materials performed better than the catalyst-cured ones. These results indicate that the production process of FRP composite materials can be simplified by using a UV lamp for curing, resulting in composite materials with the same quality, but reduced production time by about 70% compared to currently used practices. This advancement will contribute greatly to the composite material industry.

• Composites Research
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• v.35 no.4
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• pp.288-297
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• 2022

This study investigated the effect of addition of zirconia(zirconium oxide) powder on the curing behavior of phenolic resins. The heating rate controlled curing and isothermal curing behaviors of the phenol resin according to the content of the zirconia powder were analyzed. The viscosity and thermal decomposition characteristics of the phenolic resin with the zirconia content were also examind. From the DSC analysis, the degree of cure and the rate of cure were obtained. Finally, the activation energy for the cure reaction were calculated from the DSC data of the zirconia added phenolic resin. As a found, the higher the zirconia content, the longer the curing was delayed and the greater the activation energy required for curing. Additionally, the TGA result that as the content of zirconia increased, less weight loss was observed. The surface tackiness of the Carbon/Phenol prepreg was partially changed according to the zirconia content, but had no significant effect.

• Elastomers and Composites
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• v.19 no.3
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• pp.163-177
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• 1984

The effect of curing temperature increase and sulfur amount added were studied with natural and synthetic rubbers. Also, the effects of TMTD, MBTS and mixture of zinc soaps of high molecular fatty acids added to natural rubber were investigated respectively. The experimental results showed that, in the case of the conventional curing ($145^{\circ}C$), natural rubber, compared with synthetic rubber, gave higher values in elongation, tensile strength, cure rate, and lower values in modulus change. But, at high temperature curing ($180^{\circ}C$), natural rubber showed faster reversion rate, and higher heat build-up compared to synthetic rubber, than in the conventional curing. Also, natural rubber produced at high temperature showed severe degradation in hardness and tensile strength before heat-aging as well as in hardness, modulus and tensile strength after heat-aging. Improved reversion effect was obtained with natural rubber either by blending mixture of zinc soaps of high molecular acids or by applying semi-efficient vulcanization system.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.131-132
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• 2022

Looking at recent construction cases at winter construction sites, there is a risk that heat sources such as kerosene fans and fossil fuels (brown coal, molded carbon) used in concrete will cure rapidly, so in situations where further curing is impossible after formwork removal, the outer wall and the entire slab are exposed to rapid external deterioration, resulting in delays in concrete strength expression and until collapse accidents. In this study, we applied kerosene fans and tropical circulating electric heat fans mainly used as curing heat sources at construction sites, comparative analysis. also verified the performance of structures during concrete curing due to thermal convention / circulation performance, concrete demand strength expression, and implementation of electric heat fans by heavy disaster methods.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.53-54
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• 2023

In recent decades, climate change has become an issue of global importance. The calcium sulfoaluminate (CSA) cement emits lower CO₂ than the Portland cements while manufacturing. However, ettringite, which is a main hydration product of CSA cement, starts dehydrating at a temperature above 100℃, hence it may limit the CSA cement for high temperature application. Recently, an early carbonation curing of cement-based material has been extensively studied in terms of carbon neutralization. The carbonation curing of CSA cement has a potential to transform the AFt and AFm phases into calcium carbonate, and the transformation of unstable hydrates to stable hydrates can increase the resistance to elevated temperature. This review study summarizes and discusses the carbonation curing effect of CSA cement and the thermal stability of CSA cement exposed to elevated temperatures.