• Korean Journal of Plant Resources
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• v.34 no.2
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• pp.177-185
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• 2021

The purpose of this study was to compare the chemical properties of the bokbunja distributed in Korea with the content of the bioactive substance ellagic acid. The bokbunja was Rubus coreanus group and Rubus occidentalis group were compared, domestic bokbunja and import bokbunja were compared. In bokbunja, free sugar was 30.89 ± 0.7 mg/g of Rubus coreanus and 29.05 ± 0.87 mg/g of Rubus occidentalis. and 27.28 ± 7.4 mg/g of domestic bokbunja and 21.58 ± 6.73 mg/g of import bokbunja. The free amino acids was 4.50 ± 0.08 mg/g of Rubus coreanus and 5.05 ± 0.08 mg/g of Rubus occidentalis. and 4.13 ± 1.09 mg/g of domestic bokbunja and 3.75 ± 0.31 mg/g of import bokbunja. Validation of the ellagic acid method was confirmed by comparing the retention time and spectrum of the standard and extract using HPLC. The calibration curve (R²) showed linearity of 0.9999. As a result of analyzing the ellagic acid content of each extraction solvent, DMSO and methanol mixture extracts were high, and Rubus coreanus was 2.56 mg/g and Rubus occidentalis was 3.16 mg/g, which was not significantly different (p < 0.05) In addition, the ellagic acid content of domestic bokbunja and import bokbunja was 2.83 mg/g and 2.99 mg/g, which was not significantly different (p < 0.05).

• Resources Recycling
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• v.29 no.6
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• pp.15-26
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• 2020

In recent years, there is an increasing interest in environmental friendly treatment of waste-plastics in terms of the generation of microplastics. Accordingly, the recycling of waste-plastics is very important because it provides advantages of volume reduction, mitigation of carbon dioxide emission, and reproduction of value-added products. In particular, in order to recycle the eco-friendly waste-plastics, it is necessary to use a physical separation methods, and among them, flotation separation, which can separate material (i.e., polymer component) in waste-plastics is well known as a very effective separation method in terms of material recycle. Therefore, in this review, the research trend of flotation separation for effective separation of mixture waste-plastics was investigated. In addition, through the reported research results, approaches to use as new functional materials from polymers, which are raw materials for waste-plastics, are summarized.

• Applied Chemistry for Engineering
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• v.22 no.1
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• pp.37-44
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• 2011

The critical micelle concentration (CMC) of sorbitan laurate SP 20 surfactant in this paper was near $7.216{\times}10^{-4}mol/L$ and the surface tension at CMC was about 26.0 mN/m, which showed higher CMC and lower surface tension than those of octylphenol ethoxylate octylphenol ethoxylate (OPE) 10 surfactant. Dynamic surface tension measurement using a maximum bubble pressure tensiometer showed that the adsorption rate at the interface between air and surfactant solution was found to be slower with SP 20 surfactant, presumably due to a low mobility of SP 20 surfactant monomer. The contact angle of SP 20 surfactant solution was observed to decrease with an increase in surfactant concentration and showed a larger value than that of OPE 10 surfactant solution. Half-life time for foams generated with 1 wt% surfactant solution was also larger with SP 20 surfactant, which indicated higher foam stability with SP 20 surfactant. Dynamic behavior study reveals that the solubilization of n-decane oil was much lower with SP 20, which is in good agreement with experimental results of foam stability, contact angle and CMC. Dynamic interfacial tension measurement by a spinning drop tensiometer shows that interfacial tensions at equilibrium condition in both systems were almost the same but the time required to reach equilibrium was longer with SP 20.

• Applied Chemistry for Engineering
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• v.22 no.4
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• pp.376-383
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• 2011

The CMCs of LA and LA3 nonionic surfactants obtained from the reaction between glycidol and lauryl alcohol were found to be $0.97{\times}10^{-3}mol/L$ and $1.02{\times}10^{-3}mol/L$ respectively and the surface tensions for 1 wt% surfactant were 26.99 and 27.48 mN/m respectively. Dynamic surface tension measurements using a maximum bubble pressure tensiometer showed that the adsorption rate of surfactant molecules at the interface between the air and the surfactant solution was found to be relatively fast in both surfactant systems, presumably due to the high mobility of surfactant molecules. The contact angles of LA and LA3 nonionic surfactants were 27.8 and $20.9^{\circ}$ respectively and the dynamic interfacial tension measurement by a spinning drop tensiometer showed that interfacial tensions at equilibrium condition in both systems were almost the same. Also both surfactant systems reached equilibrium in 2~3 min. Both surfactant solutions showed high stability when evaluated by conductometric method and the LA nonionic surfactant system provided the higher foam stability than the LA3 nonionic surfactant system. The phase behavior experiments showed a lower phase or oil in water (O/W) microemulsion in equilibrium with an excess oil phase at all temperatures studied. No three-phase region was observed including a middle-phase microemulsion or a lamellar liquid crystalline phase.

• Applied Chemistry for Engineering
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• v.22 no.4
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• pp.353-357
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• 2011

For the purpose of introducing hydrophilic function to pristine PVDF, pristine PVDF was modified under atmosphere and aqueous vapor by irradiating electron beam (EB). EB dose was varied from 0 to 125 K Gray, respectively. Their changes of chemical composition /structure were observed and evaluated by FT-IR, EDS and DSC. Also, their surface behaviors were evaluated by contact angle. In FT-IR study, it was confirmed that hydroxyl functions were introduced to pristine PVDF. In EDS analysis, mole ratio of F (fluoride) was almost constant (about 33%) in spite of increasing EB dose, meaning that hydroxyl function was introduced via dehydrozenation, not via deflurodination. In DSC study, $T_g$ increased with increasing EB dose, which was reconfirmed that hydroxyl function was introduced via dehydrozenation. $T_m$ increased with increasing EB dose, inferring that the increase in EB dose led to more outbreak of hydroxyl function which led to more enhanced hydrogen bond. In the result of contact angle, pristine PVDF film was $62^{\circ}$ and 125 K Gray-irradiated PVDF film was even $13^{\circ}$. All results showed that pristine PVDF was successfully changed to hydrophilic PVDF.

• Applied Chemistry for Engineering
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• v.22 no.6
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• pp.610-616
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• 2011

A series of polyurethane acrylate/ZnO (PUA/ZnO) nanocomposite films with different ZnO contents were successfully prepared via a UV-curing system. The synthesis and physical properties including morphological structure, thermal properties, barrier properties and optical properties, and antimicrobial properties were investigated as a function of ZnO concentration. FTIR and SEM results showed that these PUA/ZnO nanocomposite films did not have a strong interaction between PUA and ZnO, which may lead to no increase in thermal stability. By incorporating ZnO nanoparticles, the UV blocking and antibacterial properties increased as the content of ZnO increased. Specially, the oxygen permeability in composite films changed from $2005cc/m^2/day$ to $150cc/m^2/day$ by adding the ZnO nanoparticle, which indicates that the PUA/ZnO nanocomposite films can be applied as good barrier packaging materials. Physical properties of the UV-cured PUA/ZnO nanocomposite film are strongly dependent upon the dispersion state of ZnO nanoparticles and their morphology in the films.

• Korean Chemical Engineering Research
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• v.60 no.2
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• pp.208-216
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• 2022

Surface morphology and adsorption characteristics of black and white charcoals prepared from Korean traditional kiln were quantitatively analyzed. TGA and elemental analysis of charcoals were different from produced kiln, and thermal degradation temperature and carbon content of white charcoals were apparently higher than those of black charcoals. Surface morphology shows the activation progressed through the longitudinal direction of woods and new micropores were developed to radial direction on the surface of macropores as the furthermore activation resulting in the pore connection. BET adsorption isotherms show that there are low-pressure hysteresis due to the no desorption of adsorbates, which resulted in unique Type of charcoals overlapping Type I and Type IV. Such a low-pressure hysteresis is occurred from expansion of adsorbates, which were embedded in the micropore entrances and did not get out during the desorption run. The characteristics of charcoals such as specific surface area and pore size distribution did not show correct values depending on not only produced company but also sampling sites of one piece of charcoal. Therefore, it is not easy to suggest the quantitative characteristics of charcoals prepared from Korean traditional kiln. On the other hand, preparation the quality standard of charcoal is necessary for their special uses such as adsorbent.

• Applied Chemistry for Engineering
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• v.33 no.1
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• pp.28-37
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• 2022

The lignite and bituminous coal are mainly used in thermal power plant. They exhaust green house gas (GHG) such as CO₂, and become deplete, thus require alternative energy resources. To solve the problem, the hydrochar production from biomass is suggested. In this study, both hydrothermal carbonization (HTC) and solvothermal carbonization (STC) were used to produce high quality hydrochar. To improve the reactivity of water solvent process in HTC, STC process was conducted using ethanol solution. The experiments were carried out by varying the solid-liquid ratio (1:4, 1:8, 1:12), reaction temperature (150~300 ℃) and retention time (15~120 min) using kenaf. The characteristic of hydrochar was analyzed by EA, FT-IR, TGA and SEM. The carbon content of hydrochar increased up to 48.11%, while the volatile matter decreased up to 39.34%. Additionally, the fuel characteristic of hydrochar was enhanced by reaction temperature. The results showed that the kenaf converted to a fuel by HTC and STC process, which can be used as an alternative energy source of coal.

• Applied Chemistry for Engineering
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• v.35 no.3
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• pp.214-221
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• 2024

Polyether ketone (PEEK) has been widely used in membranes because of its excellent thermal stability, chemical resistance, and significant mechanical strength. However, the melting temperature is very high, making it difficult to find suitable solvents. Therefore, in this study, PEEK and benzophenone (DPK) were used as diluents to prepare a membrane with excellent mechanical strength and chemical stability using the thermally induced phase separation (TIPS) method to compensate for the shortcomings of PEEK membrane preparation and achieving the highest performances. The optimal membrane manufacturing conditions were confirmed through the crystallization temperature and cloud point according to the polymer content through the phase diagram. Subsequently, the morphological changes of the membrane, influenced by the polymer and diluent content, were confirmed through scanning electron microscopy (SEM). Additionally, the membrane thickness tended to increase with higher polymer content. Tensile strength and DI-water permeability tests were conducted to confirm the mechanical strength and permeability of the membrane. Through the previous characteristic evaluation, it was confirmed that the membrane using PEEK had excellent mechanical strength and permeability.

• Computers and Concrete
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• v.34 no.4
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• pp.489-501
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• 2024

Geopolymers are part of a class of materials characterized by properties combining polymers, ceramics, and cement. These include exceptionally high thermal and chemical stability, excellent mechanical strength and durability in aggressive environments. This work deals with the synthesis, characterization, and sustainability evaluation of GP_GBFS-MK geopolymers by alkaline activation of a granulated blast furnace slag-metakaolin mixture. In the first step, elemental and oxide analyses by XRF and EDS showed that the main constituents of GP_GBFS-MK geopolymers are silicon, sodium, and aluminium oxides. The structural analyses by XRD and FTIR confirmed that the geopolymerization for GP_GBFS-MK geopolymers did occur, accompanied by the formation of disordered networks from the blends and a modification to the microstructure by the geopolymerization process. Similarly, the microstructural study made by SEM showed that the GP_GBFS-MK geopolymers are constituted by aluminosilicates in the form of dense clusters on which are adsorbed particles of unreacted GBFS in the form of spheroids and white residues of the alkaline activating solution. In addition, the study of the sustainability evaluation of GP_GBFS-MK geopolymers showed that the water absorption of geopolymeric materials is lower than that of OPC cement. As for the elevated temperature resistance, the analyses indicated an excellent elevated temperature resistance of GP_GBFS-MK. In the same way, the study of the resistance to chemical aggressions showed that the GP_GBFS-MK geopolymeric materials are unattackable, contrary to the OPC cement-based materials which are strongly altered.