• Polymer(Korea)
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• v.35 no.2
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• pp.176-182
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• 2011

Liquid crystalline aromatic polyesters (LCPs) are representative examples of thermotropic liquid crystalline polymers, whose structure-property relationships have been the subject of many researches. In this study, we synthesized organo-soluble liquid crystalline aromatic polyesters, and their composites with acetylene-terminated thermoset resins were prepared and characterized. Soluble LCPs were synthesized by employing 6-hydroxy-2-naphthoic acid, terephthalic acid, isophthalic acid, and 4-aminophenol as monomers via condensation polymerization based on transesterfication and transamidation. Acetylene-terminated thermoset resins were synthesized by the reaction of 4-ethynylaniline with terephthaloyl dichloride, isophthaloyl dichloride or 4,4'-biphenyldicarbonyl dichloride. We prepared the soluble LCP/thermoset composites by solution blending followed by thermal treatment. The thermal stability, thermal expansion coefficient, and dielectric properties of the composite were studied.

• Journal of the Korean Chemical Society
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• v.27 no.4
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• pp.287-293
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• 1983

Free radical-initiated copolymerizations of diethyl ${\alpha}$-phenylvinyl phospbate (DEPVP) with acrylonitrile (AN) and maleic anhydride (MAnh) were studied. The monomer reactivity ratios for AN/DEPVP pair, determined at $70^{\circ}C$ in bulk using benzoyl peroxide as an initiator, were;$ r_1(AN) = 0.77, r_2(DEPVP) = 0.002$. The values of the Alfrey-Price constants, Q and e, for DEPVP were calculated to be 0.012 and -1.35, respectively. Free radical-initiated copolymerization of MAnh/DEPVP pair in chloroform at $70^{\circ}C$ produced 1 : 1 alternating copolymers regardless monomer feed composition with the highest copolymerization rate at the molar ratio of MAnh : DEPVP = 7 : 3. The equilibrium constant of a charge-transfer complex between DEPVP and MAnh in deutrated chloroform, determinated at room temperature by transformed Benesi-Hildebrand NMR method, was 0.085 l/mol. The reduced viscosity of copolymers of AN/DEPVP pair decreased as the content of DEPVP units increased, while that of MAnh/DEPVP pair remained more or less constant.

• Fire Science and Engineering
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• v.33 no.5
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• pp.19-27
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• 2019

Fire extinguishing composite materials based on low-viscosity epoxy resin (EP) and containing 50 wt% of encapsulated fire extinguishing agent (EFA) have been studied. The positive effect of the EP on the kinetics and temperature of the EFA decapsulation was established. The EP increases the decapsulation temperature of the EFA from 130 ℃ to 155 ℃ and changes the kinetics of the decapsulation. The epoxy matrix increases the thermal stability of the EFA more than 3.9 times compared to that of the pure EFA. The protective effect of the EP on the storage stability of the EFA was validated. The mass loss of EP-containing EFA at 60 ℃ and 80% humidity over 96 h is 0.4%. The mass loss of pure EFA under the same conditions is 15%. A similar effect was observed under ultraviolet radiation: the EP-containing EFA loses 0.8% at pure EFA mass of 6%. The testing of alternative polymer matrixes has been considered.

• Korean Journal of Food Science and Technology
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• v.26 no.5
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• pp.490-495
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• 1994

Enzymatic solubilization of tofu-residue was attempted using carbohydrase isolated from Aspergillus niger CF-34. Tofu-residue, by-product of tofu manufacture or soymilk processing was used as the model for plant cell wall. It was found that tofu-residue was rich in nurients: 46.7% carbohydrate, 32.8% protein, the rest being lipid and ashes. Carbohydrate component of tofu-residue consisted of 36.8% cellulose and 62.6% hemicellulose. The carbohydrase was found to consist of pectinase, xylanase, PGase, CMCase, and SFase when tofu-residue and pectin were used as the carbon source. Enzyme induction was maximum at 7days of culture. Optimum reaction pH was 4.0, temperature $50^{\circ}C$. The enzyme was stable to $50^{\circ}C$, above which the stability decreased rapidly.

• Journal of the Korean Chemical Society
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• v.20 no.4
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• pp.309-315
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• 1976

An efficient separation method and the utilization of sericin are searched. Sericin was extracted with hot water from cocoons under atmospheric pressure. The separated sericin was gel-filtrated with Sephadex G-75 and G-150 at room temperature and at $70^{\circ}C$. The results indicated that sericin is consisted of only one fraction in elution diagram. In the graft copolymerization of acrylonitrile to sericin ceric ammonium nitrate was chosen as an initiatior. A maximum yield was obtained at certain concentration of the initiator confirming our previous experiments. Viscosity measurement of alkali-hydrolyzed graft copolymers indicated that the polyacrylonitrile graft had the molecular weight in the range of 7,000.

• Journal of the Korean Chemical Society
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• v.20 no.4
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• pp.299-308
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• 1976

Cerium (Ⅳ) ion-initiated graft copolymerizations of acrylamide and of acrylonitirile to silk fibroins were investigated. When acrylamide was used, the change in ceric ammonium nitrate concentration exhibited a maximum in degree of grafting at 0.01 M. Also observed was that the change in acetic acid content in reaction media gave a maximum in degree of grafting at 7% acetic acid in water. Degree of grafting was increased generally with increase in acrylamide concentration reaction time and reaction temperature. When acrylonitrile monomer was used for grafting,different results were obtained. Addition of nitric acid was more effective in enhancing the degree of grafting than the addition of acetic acid.Generally the grafting of acrylonitrile to silk fibroins was less efficient than the grafting of acrylamide. The portion of grafted silk fibroins insoluble in Lowe's reagent exhibited the IR absorption bands characteristics to both vinyl polymers and silk fibroins, indicating the grafting of vinyl monomers to silk fibroins. To examine the molecular weight of graft vinyl polymer, a sample of grafted silk was hydrolyzed by 10% sodium hydroxide. Viscosity measurements indicated that the molecular weight of the graft polymer was in the range of 105.

• Journal of the Korean Chemical Society
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• v.19 no.3
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• pp.198-206
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• 1975

Polymers with photosensitive functional groups, the naphthoquinone-1,2-diazide-5-sulfonyl esters(PGND, BEND and PVAND) of polyglyceryl phthalate(PG), bisphenol A-epichlorohydrin polycondensate(BE) and polyvinyl alcohol(PVA), were prepared. The molecular weights of the starting materials were determined by the cryoscopic method, i.e., in the range of 650${\sim}$1200 for PG and 780${\sim}$1320 for BE, PGND, BEND and PVAND were prepared by esterification of PG, BE and PVA with naphthoquinone-1,2-diazidie-5-sulfonyl chloride, and the replacements of such a functional groups were confirmed by the infrared absorption spectra and elemental analyses. The good agreement between the observed values of elemental analyses (PGND, BEND and PVAND) and the calculated values, indicated that the degree of polymerization did not change in the course of esterification of PG, BE and PVA.

• Elastomers and Composites
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• v.34 no.4
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• pp.360-365
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• 1999

In this study, the blends of acrylic quaternary polymer (PEBEV) which was co- polymerized from 2-ethylhexyl acrylate (2-EHA), n-butyl acrylate (BA) and ethyl acrylate (EA), vinyl acetate (VAc), and poly(vinyl chloride-co-vinyl propionate) (PVCVP) were prepared by solution blending. Pressure sensitive adhesive (PSA) properties of PEBEV/PVCVP blends were compared with those of PEBEV/poly(vinyl chloride-co-vinyl acetate) (PVCVAc) blends. Compatibility of PEBEV/PVCVP was better than that of PEBEV/PVCVAc. Tackiness of both blend systems were similar, but holding power began to decrease at 15wt% or higher PVCVAc contents in PEBEV/PVCVAc blends. On the other hands, holding power of PEBEV/PVCVP increased as the contents of PVCVP increased. Failure modes of the blends were adhesive failure except 5wt% of PVCVP was blended.

• Korean journal of applied entomology
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• v.28 no.3
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• pp.105-112
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• 1989

The nuclear polyhedrosis viruses of Bombyx mori (BmNPV) and Hyphantria cunea (HcNPV) were characterized by electron microscopic observation, SDS-PAGE of polyhedral and virion proteins, and restriction endonuclease analysis of viral DNAs. Polyhedra of BmNPV were octadecahedral in shape with the diameter of $3 \mu\textrm{m}$, whereas those of HcNPV showed irregular appearances having the diameter of $1.5~2\mu\textrm{m}$. Under alkaline protease inactivated condition, polyhedral proteins of two NPVs were resolved into a major polypeptide, 30~31 KD, and several minor polypeptides by SDS-PAGE. Examination of virion proteins by silver staining after SDS-PAGE showed that BmNPV was composed of 47 polypeptides with M.W. range of 9.6~112 KD and HcNPV was composed of 48 polypeptides with M.W. range of 9.4~111 KD. The approximate genome size of two NPVs were determined by restriction endonuclease analysis: BmNPV and HcNPV were 114.6 Kb, respectively.

• Korean Chemical Engineering Research
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• v.56 no.5
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• pp.761-766
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• 2018

Droplet-based microfluidic device has led to transformational new approaches in various applications including materials synthesis and high-throughput screening. However, efforts are required to enhance the production rate to industrial scale because of low production rate in a single droplet generator. In here, we present a method for enhancing production rate of monodisperse droplets via parallelization of flow-focusing generators. For this, we fabricated a three-dimensional monolithic elastomer device (3D MED) that has the 3D channel structures in a single layer, using a double-sided imprinting method. We demonstrated that the production rate of monodisperse droplet is increased by controlling the flow rate of continuous and dispersed phases in 3D MED with 8 droplet generators. Thus, we anticipate that this microfluidic system will be used in wide area including microparticle synthesis and screening system via encapsulation of various materials and cells in monodisperse droplets.