• Title/Summary/Keyword: molecular weight distribution

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Determination of Molecular Weight and Molecular Weight Distribution of Polypropylene Using Rheological Properties (유변학적 물성을 이용한 폴리프로필렌의 분자량과 분자량 분포를 결정하는 방법)

  • Lee, Young Sil;Yoon, Kwan Han
    • Polymer(Korea)
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    • v.38 no.6
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    • pp.735-743
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    • 2014
  • The rheological measurement of polypropylene (PP) has been performed using a rheometer, an intrinsic viscometer, and an MI machine to predict the molecular weight and the molecular weight distribution. Also, GPC has been used for the determination of the molecular structure. The distribution broadness parameter using modified Carreau model has been used to make the correlation between the rheological parameter and the molecular structure instead of the rheological PI (polydispersity index) which is determined from the cross of modulus from the dynamic oscillatory measurement. Even though the rheological PI is useful to determine the molecular weight distribution of the PP using controlled rheology, which has narrow and uniform molecular weight distribution, but not suitable to determine the molecular weight distribution of the PP made from direct polymerization which has broad and various molecular weight distribution. However the distribution broadness parameter which determined from the index of the shear thinning of the PP melt well predicts the molecular weight distribution of PP.

Study on the Molecular Weight Distribution Curve of Cellulose Triacetate Acetylated Under Various Temperatures (醋酸纖維素의 醋化溫度가 分子量分配曲線에 미치는 影響)

  • Kim, Dong-Il;Noh, Ick-Sam;Cha, Kyong-Mo
    • Journal of the Korean Chemical Society
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    • v.4 no.1
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    • pp.44-50
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    • 1957
  • Fibrous cellulose triacetate prepared from purified cotton under various temperatures was dissolved in the solution of 70%, monochloroacetic acid and it was fractionated using water as a precipitant. Eight fractions were obtained through the stepwise precipitation. Degree of polymerization and molecular weight of each fraction were measured viscometrically. Integral and differential molecular weight distribution curve were drawn for each sample prepared under various temperatures and were carefully observed. On this experimental study, following conclusions were obtained: Fractional precipitation can be carried out for fibrous cellulose triacetate in the solution of 70% monochloroacetic acid using water as a precipitant. The differences on the shapes of molecular weight distribution curve were occured on account of the various acetylation temperatures. At the relatively higher acetylation temperatures, the cellulose was randomly degraded and the portion of low degree of polymerization was increased. Commercial acetate, therefore, may not be prepared at above 40$^{\circ}C$ according to the molecular weight distribution curve regardless of higher viscosity and average degree of polymerization. It was concluded that the optimum acetylation temperature for commercial acetate was approximately 30$^{\circ}C$.

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Size Characterization of Sodium Hyaluronate by Field Programming Frit Inlet Asymmetrical Flow Field-Flow Fractionation/Multiangle Light Scattering

  • Kim, Hoon-joo;Lee, Hee-jeong;Moon, Myeong-Hee
    • Bulletin of the Korean Chemical Society
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    • v.27 no.3
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    • pp.413-418
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    • 2006
  • Sodium hyaluronate (NaHA), water soluble polymer having ultra-high molecular weight, is characterized by using on-line frit inlet asymmetrical flow field-flow fractionation (FI-AFlFFF) and multiangle light scattering (MALS). This study demonstrates the capability of power programming FI-AFlFFF for the separation of NaHA and the applicability of FI-AFlFFF with MALS for the characterization of molecular weight distribution and their structural information. Since sample injection and relaxation in FI-AFlFFF are achieved by using hydrodynamic relaxation, separation of high molecular weight polymers can be achieved smoothly without halting the separation flow. Experiments are carried out with the two different NaHA products (a raw NaHA sample and a thermally degraded NaHA product) and molecular weight distribution and conformations in solution are determined. Influence of sample filtration on the change of molecular weight distribution is also discussed.

Molecular Weight Distribution of Rosin Modified Phenol Resin Used in Media for Printing Varnishes. (인쇄잉크용 로진변성 페놀수지의 분자량 분포에 관한 연구)

  • SungBinKim
    • Journal of the Korean Graphic Arts Communication Society
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    • v.7 no.1
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    • pp.65-72
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    • 1989
  • Modified phenolics can have a retarding effect on the gelation of wood oil. Modified phenolic resins can be used in media for paint, varnishes, primers, overprinting varnishes, litho, letterpress and rotogravure inks. Varnishes based on rosin phenolic are faster drying, have better durability, are harder and glosser, and have greater resistance to water than ones based on ester gums. These physical properties is concerned with molecular weight distribution of rosin modified phenol resin. This paper was studied about molecular weight distribution of rosin phenolics which were prepared between $130~250^{\circ}C$. The results were as follows: 1) Average molecular weights inereased with increasing reaction temperature. 2) $M_w/M_n$ were from 3.43 to 46.44 with increasing reaction temperature and so the molecular weight distributions were changed from random distribution to broad distribution. 3) The relation ship between intrinsic viscosity and weight average molecular weight was follows: $[{\;}{\;}]={\;}1{\times}{\;}10^{-6}M_w,{\;}M_w=M_w$ 4) Esterification reaction between the acid group of rosin and polyol was started about $230^{\circ}C$$.

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Analysis of Low Molecular Weight Collagen by Gel Permeation Chromatography

  • Yoo, Hee-Jin;Kim, Duck-Hyun;Park, Su-Jin;Cho, Kun
    • Mass Spectrometry Letters
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    • v.12 no.3
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    • pp.81-84
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    • 2021
  • Collagen, which accounts for one-third of human protein, is reduced due to human aging, and much attention is focused on making collagen into food to prevent such aging. Gel permeation chromatography with Reflective Index (RI) detection (GPC/RI) was chosen as the most suitable instrument to confirm molecular weight distribution, and we explored the use of this technique for analysis of collagen peptide molecular sizes and distributions. Data reliability was verified by matrix-assisted laser desorption/ionization coupled to time-of-flight (MALDI-TOF) mass spectrometric analysis. The data were considered meaningful for comparative analysis of molecular weight distribution patterns.

Molecular Weight Distribution of Regenerated Silk Fibroin in Aqueous Solution

  • Jeong, Jae-Ho;Hur, Won
    • 한국생물공학회:학술대회논문집
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    • 2003.10a
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    • pp.621-625
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    • 2003
  • In order to investigate the properties of aqueous fibroin solution, the molecular weight distribution of silk fibroin was determined by gel filtration chromatography. The molecular weights spreaded from 200 kDa to less than 20 kDa. The distribution of molecular weight was significantly affected when the pH of solubilization solution is less than 1. Distributions of fibroin solution stored at various condition were also investigated.

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Effect of Solubilization Conditions on Molecular Weight Distribution of Enzymatically-Hydrolyzed Silk Peptides (실크의 가용화 조건이 효소분해 실크 펩타이드의 분자량 분포에 미치는 영향)

  • 채희정;인만진;김의용
    • KSBB Journal
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    • v.13 no.1
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    • pp.114-118
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    • 1998
  • The effects of fibron solubilization conditions on molecular weight distribution of enzymatically-hydrolyzed silk peptides were investigated. The weight-averaged molecular weights of silk proteins prepared by solubilization with calcium chloride, ethylenediamine and sulfuric acid were 41600, 3308, and 1268 dalton, respectively. Silk peptides in the average molecular weight range of 600-1200 dalton were obtained by protease treatment from solubilized silk fibroin. After the acid hydrolysis of silk protein using hydrochloric acid for 24 hr, silk protein was hydrolyzed to peptides whose average molecular weight and free amino acid content were 145 dalton and 80%, respectively. It was possible to control molecular weight distribution of silk peptides by the combination of solubilization and hydrolysis methods. Among the various treatment methods, acid solubilization followed by protease treatment had an advantage of molecular weight control for the peptide production.

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Structure and Property Modification of Bimodal Molecular Weight Distribution Polyethylene by Electron Beam Irradiation

  • Lee, Sang-Man;Jeon, Hye-Jin;Choi, Sun-Woong;Song, Hyun-Hoon;Nho, Young-Chang;Cho, Kyu-Cheol
    • Macromolecular Research
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    • v.14 no.6
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    • pp.640-645
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    • 2006
  • Polyethylene of bimodal molecular weight distribution was irradiated with an electron beam. The thermal and mechanical properties were examined by DSC, small and wide angle X-ray scattering and static tensile test according to the crystal morphology of the irradiated samples. The crystal morphology change upon irradiation, as revealed by wide angle X-ray scattering, correlated well with the changes in melting enthalpy, whereas the lamellar thickness and the amorphous gap thickness remained virtually unchanged at irradiation doses up to 500 kGy. Crosslinks in the crystal domains became evident at an energy level of 250 kGy, resulting in reduced crystallinity and crystal size of the (110) and (200) planes. The samples became stiff and brittle with increased irradiation dose, which seem to be more relevant to the amount of cross links than the crystal morphology changes.

Contrasting Correlation in the Inhibition Response of ADP-induced Platelet Aggregation and the Anti-coagulant Activities of Algal fucoidans Derived from Eisenia bicyclis and Undaria pinnatifida sporophylls (Mekabu)

  • Jeong, Eui-Sook;Yoon, Yeon-Hee;Kim, Jong-Ki
    • Fisheries and Aquatic Sciences
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    • v.12 no.3
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    • pp.194-202
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    • 2009
  • Sulfated fucans are known to have both anti-thrombotic and anti-coagulant activities. In this study, the variation in platelet aggregation and anti-coagulant activities was investigated in vitro with regard to administered dose, molecular weight distribution, sulfate content, and sugar composition in two algal fucoidans from Eisenia bicyclis and Undaria pinnatifida sporophylls (Mekabu). The anti-coagulant activity largely correlated with sulfate content and with molecular weight distribution in a dose-dependent manner. However, both fucoidans demonstrated inhibitory responses to ADP-induced platelet aggregation in dose- and structure-dependent manners that contrasted with the anti-coagulant activity. Neither molecular weight distribution nor sulfate content greatly affected platelet-aggregation inhibition (PA-inhibition) by the fucoidan fractions, whereas anti-coagulant activity was sensitive to these structural factors. Interestingly, an E. bicyclis fucoidan fraction exhibited almost complete PA-inhibition at a treatment dose of 500 mg/mL while retaining weak anti-coagulant activity. In conclusion, these observations suggest that fucoidan may be a useful anti-thrombotic or anti-platelet agent in various arterial thrombotic disorders, including post-vascular intervention with controlled bleeding complications, due to its anti-coagulant modulating activity.