• Applied Chemistry for Engineering
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• v.9 no.2
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• pp.226-231
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• 1998

Hot melt adhesive which is solventless type has been widely used due to the possibility of automated adhesion process. The main purpose of this study is the development of polyamide based hot melt adhesive to improve the property of conventional ethylene-vinyl acetate hot melt adhesive, which has an inherent problem against heat resistance. In this study, it was found that the terpolymers of nylon 6, nylon 66, and nylon 12(CM831, 843P types) instead of nylon homopolymer were suitable base resins for hot melt adhesive, since the disruption of regularity in the polymer chains reduced the crystallinity, resulting in lower melting point and melt viscosity. According to the results, the optimum adhesion property could be obtained by the using 75/25~50/50 weight radio of CM831/843P resin as a base resin. Terpene resin was used as tackifier to improve adhesion and wetting properties. The best result can be obtained with the 10 wt.% addition of terpene resin. The terpene resin acted as proper tackifier in this system which decreased the melt temperature and viscosity, but increased the mechanical strength of adhesive itself. Also, the rheological property of the adhesive changed from typical non-Newtonian behavior to Newtonian behavior as terpene resin was added.

• Membrane Journal
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• v.24 no.6
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• pp.453-462
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• 2014

Thin film composite (TFC) polyamide (PA) membranes were prepared on polyester (PET) nonwoven reinforced polysulfone supports for forward osmosis (FO) processes. PSF (polysulfone) supports were prepared via the phase inversion process from PSF casting solutions in dimethyl formamide (DMF) solvents (19 wt%) by using a PET nonwoven (thickness of $100{\mu}m$) as a mechanical reinforcing material for reverse osmosis (RO) membrane. The PSF support from 19 wt% of DMF/PSF casting solution showed sponge-like morphology and asymmetric internal structure. To reduce the internal concentration polarization in FO operation, thin ($20{\mu}m$ of thickness) nonwoven-supported PSF supports were prepared by using PSF/DMF casting solution (9~19 wt%). A desirable support structure with a highly porous sponge-like morphology were achieved from the thin nonwoven-supported PSF layer prepared with 9~12 wt% casting solution. A crosslinked aromatic polyamide layer was fabricated on top of each support to form a TFC PA membrane. The tested sample from 12 wt% of DMF/PSF casting solution presented outstanding FO performance, almost 5.5 times higher water flux (24.3 LMH) with low reverse salt flux (RDF, 1.5 GMH) compared to a thick nonwoven rainforced membrane (4.5 LMH of flux and 3.47 GMH of RSF). By reducing the thickness of the nonwoven and optimizing PSF concentration of casting solution, the morphology of the prepared membranes were changed from a dense structure to a porous sponge structure in the boundary area between nonwoven and PET support layer.

• Journal of dental hygiene science
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• v.10 no.6
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• pp.445-450
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• 2010

The aim of this study was to evaluate the effect according to the fiber type and combination on the reinforcement of heat-polymerized denture base resin. The heat-polymerized resin(Vertex RS, Dentimax, Netherlands) was used in this study. Glass fiber(GL; ER 270FW, Hankuk Fiber Glass, Korea), polyaromatic polyamide fiber(PA; aramid; Kevlar-49, Dupont, U.S.A.) and ultra high molecular weight polyethylene fiber(PE, polyethylene; P.E, Dong Yang Rope, Korea) were used to reinforce the denture base resin specimens. The final size of test specimen was $64mm{\times}10mm{\times}3.3mm$. The specimens of each group were stored in distilled water at $37^{\circ}C$ for 50 hours before measurement. The flexural strength and flexural modulus were measured by an universal testing machine(Z020, Zwick, Germany) at a crosshead speed of 5 mm/min in a three-point bending mode. In this study, all fibers showed reinforcing effects on denture base resin(p<0.05). In terms of flexural strength and flexural modulus, glass fiber 5.3 vol.% showed most effective reinforcing effect on heat polymerized denture base resin. For flexural modulus, PA/GL was the highest in denture base resin specimen for hybrid FRC using two combination (p<0.05). Glass fiber 5.3 vol.% and PA/GL are considered to be applied effectively in reinforcing the heat polymerized denture base resin.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.9
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• pp.1518-1523
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• 2013

To estimate the shelf life of red cabbage sprouts (stored at 4 and $10^{\circ}C$), the numbers of total aerobic bacteria were determined during storage. Parameters for the Gompertz model were determined and the shelf life was predicted using a modified Gompertz equation. The estimated shelf lives of red cabbage sprouts packed with polyolefin film and polyamide/polyamide/polyethylene (PA/PA/PE) film at $4^{\circ}C$ were 49.4 and 52.3 h, respectively, whereas those of red cabbage sprouts packed with polyolefin film and PA/PA/PE film at $10^{\circ}C$ were 19.7 and 22.6, respectively. The shelf life prediction equation was appropriate, based on the statistical analysis of the accuracy factor, bias factor, and mean square error. On the other hand, for red cabbage sprouts treated with aqueous $ClO_2$/fumaric acid and UV-C then packed with polyolefin film or PA/PA/PE film, the shelf life was predicted to be longer than 168 h. These results suggest that the combined treatment of aqueous $ClO_2$/fumaric acid and UV-C can be useful for improving microbial safety and extending the shelf life of red cabbage sprouts during storage.

• Membrane Journal
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• v.33 no.6
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• pp.427-438
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• 2023

In this study, in order to improve the performance of the reverse osmosis membrane with high water flux and high salt rejection, a study was conducted on the evaluation of characteristics according to the curing temperature and time during various additives and interfacial polymerization. The morphology of the membrane with no additives and the membrane with additives both showed a "rigid-and-valley" structure, confirming that the polyamide layer was successfully polymerized on the surface of the porous support layer. In addition, the additive of 2-Ethyl-1,3-hexanediol (EHD) had improved hydrophilicity and water flux, which was confirmed by measuring the contact angle. Finally, a highly permeable TFC membrane with NaCl and MgSO₄ salt rejection of 97.78% and 98.7% and a high water flux of 3.31 L/(m²⋅h⋅bar) was prepared.

• Applied Chemistry for Engineering
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• v.10 no.8
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• pp.1136-1140
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• 1999

Melt blends of polymide 6(PA6) and polypropylene grafted maleic anhydride(PP-g-MA) were prepared to study the influence of chemical reaction between the two polymer components. The tensile, flexural, izod impact, dynamic mechanical properties and phase structure were investigated for this blend system. Tensile strength and modulus of the blends showed synergetic effect upon blending of two polymer components. Flexural properties maintained the value of numerical mean calculated from the weight ratio of two components. Also, notched izod impact strengths showed maximum in th PA6/PP-g-MA 50/50 wt % blend. From the change of tan ${\delta}$ observed, we confirmed the increase of miscibility in this blend system by chemical reaction between PA6 and PP-g-MA. Blends of good impact resistance could be obtained when the PP-g-MA particles of $2{\mu}m$ was dispersed in the PA6 matrix.

• Membrane Journal
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• v.23 no.6
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• pp.439-449
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• 2013

This study investigated the aromatic polyamide reverse osmosis membrane was modified with diphenylamine (DPA) for enhanced chlorine and fouling resistance and how to optimize. DPA has high reactivity and thermo chemical stability. The performance of a modified membranes was investigated and its surface analyzed using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and contact angle measurement. The experiment was conducted while changing the conditions of temperature and DPA solution concentration.

• Textile Coloration and Finishing
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• v.14 no.4
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• pp.229-239
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• 2002

Colorants were extracted from the heartwood of sappan lin. with MeOH under reflux, and the concentrate or the powder of dye was prepared by low pressure concentration method using suitable organic solvent. Various components were isolated from sappan wood, and the chemical structure and mechanism of compound having the excellent antibacterial and deodorization properties were analyzed. The results obtained are as follows ; The seventeen components of sappan wood were seperated by HPLC chromatography, and the five components among them were existed more than 6% and the other components were existed lower than 0.6%. The resolving powers of the non-polar solvent and polar solvent systems were evaluated by their ability to resolve the samples. It showed that chloroform-methanol-water(800:150:10) system has the best resolving power. Although the seperation rate is very slow, polyamide C-100 column chromatography gives a clear seperation of sappan wood. On the basis of the spectrometric data such as IR, UV, $GC-Mass,\;^1H-NMR,\;^{13}C-NMR\;and\;^1H-^{ 13}C-NMR$, the chemical structure of compound haying the excellent antibacterial and deodorization properties was established as brazilin containing the functional groups such as two quaternary carbon, one benzyl carbon, methylene contiguous to oxygen and methylene caused by oxygen atom.

• Design & Manufacturing
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• v.1 no.1
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• pp.1-5
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• 2007

Double injection molding process is very efficient molding-method for molding the products which is consist of multi-materials. Fuel-tube holder which is necessary for automobil power train and circulation systems is composed of plastic and rubber materials to minimize the vibration and pulsation noises. In existing process, fuel-tube holder was made by the insert molding process or assembly process after molding. If fuel-tube holder is manufactured by double injection molding process, it may be realize to improve the product quality, efficiency of molding-process and retrenchment of manufacturing cost. In this study, for manufacturing fuel-tube holder by double injection molding process, the analysis of joining characteristics between PA6(polyamide 6) and TPE(thermoplastic elastomer) was executed and the double injectin mold for molding fuel-tube holder with core toggle mechanism was fabricated. Finally, fuel-tube holder was molding using fabricated double injection mold.

• Membrane and Water Treatment
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• v.8 no.6
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• pp.613-623
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• 2017

We report the novel thin film composite RO membrane modified by graphene oxide. The thin film composite RO membrane was exposed to 2000 mg/l sodium hypochloride; thereafter it was subjected to different graphene oxide concentration ranging from 50 mg/l to 1000 mg/l in water. The resultant membrane was crosslinked with 5000 mg/l N-hydroxysuccinimide. The performance of different membranes were analysed by solute rejection and water-flux measurement. It was found that 100 mg/l graphene oxide exposure followed by 5000 mg/l N-hydroxysuccinimide treatment resulted in the membrane with the highest solute rejection of 97.78% and water-flux of 4.64 Liter per sqm per hour per bar g. The membranes were characterized by contact angle for hydrophilicity, scanning electron micrographs for surface morphology, energy dispersive X-Ray for chemical composition of the surface, Atomic force microscope for surface roughness, ATR-FTIR for chemical structure identification. It was found that the graphene oxide modified membrane increases the salt rejection performance after exposure to high-fouling water containing albumin. Highly hydrophilic, antifouling surface formation with the nanomaterial led to the improved membrane performance. Moreover, the protocol of incorporating nanomaterial by this post-treatment is simple and can be applied to any RO membrane after it is manufactured.