• Title, Summary, Keyword: 가교화

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Physicochemical Properties of Cross-linked and Partially Enzymatically Hydrolyzed (CLE) Waxy Rice Starch (가교화 후 효소처리(CLE) 찹쌀 전분의 물리화학적 특성)

  • Yu, Chul;Kim, Sung-Woo;Kim, Chong-Tai;Choi, Sung-Won;Kim, Byung-Yong;Baik, Moo-Yeol
    • Korean Journal of Food Science and Technology
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    • v.40 no.3
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    • pp.290-296
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    • 2008
  • This study examined the physicochemical properties of chemically and enzymatically cross-modified waxy rice starches. The waxy rice starch was cross-linked using phosphorous oxychloride, and then partially hydrolyzed with four commercial ${\alpha}$-amylases (Fungamyl, Termamyl, Liquozyme, Kleistase). Swelling power and the moisture sorption isotherm did not change with cross-modification. Two cross-modified waxy rice starches (hydrolyzed with Termamyl and Liquozyme) showed higher solubilities than native starch and the two other cross-modified starches (hydrolyzed with Fungamyl and Kleistase). In terms of RVA characteristics, the two cross-modified waxy rice starches hydrolyzed with Termamyl and Liquozyme, respectively, had lower peak viscosity, holding strength, and final viscosity than the native starch. However, the two starches hydrolyzed with Fungamyl and Kleistase, respectively, revealed higher peak viscosity, holding strength, and final viscosity than the native starch. No differences were displayed in the X-ray diffraction patterns and DSC thermal characteristics of the cross-modified waxy rice starch as compared to both the native and cross-linked starches, indicating that cross-linking and enzymatic hydrolysis occurred in the amorphous region and did not alter the crystalline region.

Crosslinking of Poly(2,6-dimethyl-1,4-phenylene oxide) Anion Exchange Membranes (폴리페닐렌 옥사이드 음이온 교환막의 가교결합)

  • Lee, Seung-Gwan;Kim, Mi-Yang;So, Won-Wook;Kang, Kyung-Seok;Kim, Kwang-Je
    • Membrane Journal
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    • v.28 no.5
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    • pp.326-331
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    • 2018
  • Crosslinking of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) anion exchange membranes, which can be used for capacitive deionization (CDI), was investigated. PPO Anion exchange polymer was prepared through bromination and amination reaction steps and crosslinked with bisphenol A diglycidylether (BADGE), m-phenylenediamine (m-PDA), and hexamethylenediamine (HMDA). The gelation time by crosslinking was short in the order of HMDA > m-PDA > BADGE. The anion exchange membranes crosslinked at room temperature over a certain amount of crosslinking agent did not dissolve in an aprotic solvent such as 1-methylpyrrolidone (NMP) and the chemical durability of their membranes to organic solvent increased. The ion exchange capacity and water uptake of anion exchange membranes crosslinked with different crosslinker (BADGE) contents were measured and compared. The CDI performance of the crosslinked PPO anion exchange membrane immersed in the HMDA solution was almost the same as that of the non - crosslinked membrane except for the initial stage of the adsorption step.

Self-employment as Bridge Employment (자영업과 가교일자리)

  • Sung, Jaimie;Ahn, Joyup
    • Journal of Labour Economics
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    • v.27 no.2
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    • pp.1-27
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    • 2004
  • The share of self-employment shows a downward trend until 1990 and then an upward trend since then. The upward trend is mainly due to more employers and more male self-employed, which implies that self-employment plays a significant role as an alternative form of employment. This paper examines whether self-employment can be a bridge between no work and wage work in the processes entering into or exiting labor market, and if so, what determines the choice of self-employment as a bridge, using the data from the Korea Labor and Income Panel Survey(Wave 1 to Wave 5). Empirical analysis employing the probit model shows that the older, female, the less educated, and persons with bad health are more likely to choose self-employment as a bridge in the exit process and that they are less likely to choose it as a bridge in the entry process. Business cycle has a statistically significant negative effect on its role of bridge employment in the exit process but not in the entry process. The result implies that, in the ageing society, labor market policy should consider self-employment as a better alternative than wage work for the aged.

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Effects of Annealing Conditions of Corn Starch Slurry on the Formation of Phosphorylated Cross-linked Resistant Starch (옥수수 전분유의 Annealing 조건이 인산가교 저항 전분의 형성에 미치는 영향)

  • Bae, Chun-Ho;Park, Heui-Dong
    • Korean Journal of Food Preservation
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    • v.19 no.2
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    • pp.216-222
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    • 2012
  • The optimum annealing conditions of corn starch slurry were studied for RS4 type resistant starch production by phosphorylated cross-linking. When a corn starch slurry was cross-linked by using phosphate salts (STMP/STPP mixture) in the presence of 0.9%, 1.2% and 1.5% NaOH/st.ds, a high concentration of NaOH resulted in a rapid increase of the RS contents at the early reaction stage. However, similar RS contents were obtained after 12 h of cross-linking regardless of NaOH concentrations. The annealing treatment was conducted under various conditions such as pH between 2-10, temperature $40-60^{\circ}C$, time 0-14 h followed by phosphorylated cross-linking. The lower slurry pH was for the annealing treatment, the higher RS contents were obtained after cross-linking. When the slurry annealed for various period of time and temperature, a maximal amount of RS was formed after 2 h of annealing at $50^{\circ}C$ of annealing temperature of the starch slurry (pH 2.0). Therefore, an optimal annealing conditions at pH 2.0 and $50^{\circ}C$ for 2 h were proposed under the cross-linking conditions of sodium sulfate 10%/st.ds, NaOH 1.2%/st.ds and 12 h of the reaction time. The RS contents were linearly increased with the increase of phosphate salt addition. The RS4 prepared under the optimal conditions contained RS 72.3% and its phosphorus content was 0.36%/st.ds, which was below the limit (0.4%/st.ds) of modified starch by Korea Food Additives Code.

Temperature Dependence on the Binding of the Homologs of Methyl Orange by Crosslinked Poly(4-vinylpyridine). 6. Effect of Crosslinking Agent (가교폴리 (4-비닐피리딘) 과 메틸오렌지동족체와의 결합에 대한 온도의 존성. 6. 가교제의 영향)

  • Lee, Suck-Kee;Park, Nam-Kyu;Kim, Woo-Sik
    • Applied Chemistry for Engineering
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    • v.1 no.2
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    • pp.182-189
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    • 1990
  • Various crosslinked poly(4-vinylpyridines) having different degrees of crosslinking were prepared by radical copolymerizations of 4-vinylpyridine with N, N'-2, 6-pyridinebisacrylamide as a crosslinker. The abilities of these crosslinked polymers to bind methyl orange and butyl orange were investigated at various temperatures in a buffer solution of pH 7. The first binding constants were evaluated from the equilibrium binding amounts. The first binding constants against the temperatures showed bell-shaped curves. Also, the first binding constants against the degree of crosslinking showed bell-shaped curves. When the temperature and the degree of crosslinking of maximum binding in the curves of these binding systems were compared with those of previous systems containing crosslinked poly(4-vinylpyridines) prepared by using N, N'-methylenebisacrylamide, N, N'-tetramethy-lenebisacryamide and divinylbenzene as crosslinkers, respectively, they were varied with the crosslinked poly(4-vinyl pyridines) containing different crosslinkers. These results were discussed in terms of the properties of the crosslinkers.

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Catalyst Effects on Cross-linking of a Multi-Functional Fluoropolymer/Blocked-HMDI Blends (다기능성 함불소고분자/Blocked-HMDI 블렌드계의 가교화 반응에서의 촉매 영향)

  • Ahn, Won-Sool
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.13 no.5
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    • pp.2408-2413
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    • 2012
  • Effects of stanous catalyst on the cross-linking reaction characteristics of multi-functional fluoropolymer with blocked-hexamethylene diisocyanate(HMDI) were studied by dynamic DSC and non-isothermal thermogravimetric analysis (TGA). Results showed that cross-linking reaction occurred around $230-250^{\circ}C$ aftr the solvent and phenol, blocking agent, were removed upto the $150^{\circ}C$. It was considered that the reaction mechanism of the multi-functional fluoropolymer with HMDI might not be changed by the catalyst, however, the reaction rate became extremely faster upto to 100 times, showing the change of activation energy 81.8 kJ/mol for non-catalytic system to 61.7 kJ/mol for 1 phr catalytic system.

Immobilization of $\beta$-glucosidase and properties of Immobilized Enzyme ($\beta$-glucosidase의 고정화와 효소 반응특성)

  • 정의준;이상호이용현
    • KSBB Journal
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    • v.5 no.2
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    • pp.141-149
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    • 1990
  • $\beta$-glucosidase derived from Aspergillus niger was immobilized by (1) covalent linkage on chitin and chitosan with glutaraldehyde, (2) adsorption on DEAE-cellulose and Amberite IRA93 after succinylation, and (3) entrapment on alginate and polyacrylamide gels with various cross linking agents. The retention yield of $\beta$-glucosidase immobilized on chitosan was 31.5% and operational stability was 69% after continuous operation at column reactor(5$0^{\circ}C$ at pH 4.8) for 15 days. The retention yield and operational stability were 24.7% and 60% respectively, in adsorption on Amberite IRA 93. On the other hand, the entrapment method by alginate and polyacrylamide gel was identified to be not appropriate due to the continuous elution of inlmobilized $\beta$-glucosidase. Optimum conditions for the immobilization on chitosan were also studied with optimum pH of 4.8 and glutaraldehyde concentration of 0.4%(w/v). The properties and stability of immobilized $\beta$-glucosidase are also investigted. The conversion yield of cellobiose to glucose was also analyzed using the column type enzyme reactor to evaluate the effectiveness of immobilized enzyme.

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Preparation and Characterization of Chitosan Membranes Cross-linked Using Poly(2,6-dimethyl-1,4-phenylene oxide) Polymer and Chitosan (Poly(2,6-dimethyl-1,4-phenylene oxide) 고분자와 키토산을 이용한 가교막 제조 및 특성평가)

  • Son, Tae Yang;Ko, Tae Ho;Jung, Ji Hye;Hong, Jun Ui;Nam, Sang Yong
    • Membrane Journal
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    • v.28 no.3
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    • pp.205-213
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    • 2018
  • In this study, cross-linked membrane were successfully prepared by using brominated PPO (Br-PPO) as the main polymer chain. Chitosan and quaternary ammonium modified chitosan (QA-chitosan) was used as the cross linking agents. The cross linked membranes were post-functionalized by using trimethylamine solution. The degree of cross linking was also controlled by varying the ratio of cross linking agent. The applicability of the cross-linked membrane (A-PPO + chitosan, A-PPO + QA-chitosan) as ion exchange membranes was verified through various characterization techniques. The cross-linked membrane using QA-chitosan as cross linking agent was found to be better in performance than the membrane using pristine chitosan cross linking agent. As the percentage of QA-chitosan increased, the ion exchange capacity from 1.18 meq/g to 1.53 meq/g and water uptake from 21.6% to 42.2% was improved.

Pwevaporation Separation of Aqueous Ethanol Solution Through Poly(vinyl alcohol) Membranes Crosslinked Poly(acrylic acid-co-maleic acid) (Poly(acrylic acid-co-maleic acid)로 가교된 Poly(vinyl alcohol)막을 이용한 에탄을 수용액의 투과증발분리 특성)

  • 남상용;성경수;천세원;임지원
    • Membrane Journal
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    • v.12 no.4
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    • pp.255-261
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    • 2002
  • Poly(vinyl alcohol) (PVA) membranes crosslinked with poly(acrylic acid-co-maleic anhydride) (PAM) as a polymeric crosslinking agent were prepared to investigate the pervaporation performance for the dehydration separation of aqueous ethanol solution. The characteristics of the resulting membranes crosslinked(x) were analysed by FT-IR and water swelling test. The water swelling decreased with increasing crosslinking agent content. The crosslinked PVA membranes with PAM showed lower water swelling than those of PVA membrane crosslinked with glutaraldehyde and modified PVA membrane. The swelling of water molecules in the crosslinked PVA membranes is more restricted by both chemical crosslinking between PVA and polymeric crosslinking agent chains and physical crosslinking by the entanglement between the PVA and polymeric crosslinking agent chains. For the pervaporation of aqueous ethanol solution through the crosslinked membrane, as the contents of crosslinking agent increased, the separation factor increased while the permeation flux decreased. The separation factor slightly decreased and permeation flux increased with increasing feed water content. As a result it could be considered that PVA-PAM membranes suppressed the plasticization effect even in the range of high water concentration in fled.

Radiation Crosslinking and Shrinkable Properties of PVC (PVC의 방사선 가교와 열수축 특성)

  • Nho, Young Chang
    • Applied Chemistry for Engineering
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    • v.3 no.2
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    • pp.341-348
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    • 1992
  • PVC was compounded with various crosslinking agents, plasticizers and acrylonitrile butadiene rubber(NBR) to evaluate their effects on the radiation gel percent, elongation at break, heat distortion and heat shrinkage. Gel yield of PVC increased with increasing unsaturation levels per molecular weight of crosslinking agents while PVC containing NBR was more sensitive to crosslinking than PVC itself regardless of the types of crosslinking agents and plasticizers. It was found that gel percent was increased with increasing radiation dose, while heat distortion was decreased with increasing gel percent. Heat shrinkage was increased with decreasing stretching temperature and increasing annealing temperature.

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