• Journal of the Korean Wood Science and Technology
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• 제45권4호
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• pp.471-481
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• 2017

As the molecular weight (MW) of urea-formaldehyde (UF) resins had a great impact on their properties, this work was conducted to study effect of analytical parameters of gel permeation chromatography (GPC) on the MW measurement of UF resins. GPC parameters such as flow rate, column, detector temperature, and sample injection temperature were selected to compare number-average molecular weight (Mn), weight-average molecular weight (Mw), molecular weight distribution (MWD) and polydispersity index (PDI) of two UF resins with different viscosities. As expected, UF resin with higher viscosity resulted in greater Mn and Mw than those of low viscosity UF resin. When the flow rate increased, both Mn and Mw of UF resins decreased and MWD became narrower. By contrast, both Mn and Mw increased and MWD became wide when the column, detector, and sample injection temperature increased. The column, detector, and sample injection temperature of $50^{\circ}C$ at a flow rate of $0.5m{\ell}/min$ resulted in the highest MW and broadest MWD for the GPC analysis. These results suggest that the apparent molecular size or a hydrodynamic radius of UF resin molecules dissolved in the mobile phase affect to Mn, Mw and MWD.

• 한국수산과학회지
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• 제39권4호
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• pp.313-317
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• 2006

To prepare oligouronic acids from high-molecular-weight alginates, sea tangle (Laminaria japonica) alginates were hydrolyzed at various pHs for 1 hr at 80$^{\circ}C$. The effects of hydrolysis pH (HpH) on the average molecular weight (AMW) and MW distribution ratios (DRs) in the hydrolyzed alginates were investigated. As HpH decreased, the DRs of the alginates with MW>500 kDa and MW=300-500 kDa decreased exponentially, while it increased exponentially for MW<50 kDa. For MW=100-300 kDa, DR increased exponentially as HpH fell from 5.0 to 3.5, and then decreased exponentially. Similarly, for MW=50-100 kDa, DR increased exponentially as HpH increased to 1.0 from 5.0, and then decreased exponentially. As HpH decreased, the MW cutoff size and AMW of alginates fraction with the highest DR were decreased. For HpH 4.5 and 5.0, the MW cutoff size with the highest DRs was MW=300-500 kDa; the DRs were 28.9 and 32.6%, respectively; and the AMW of both was about 400 kDa, for HpH 3.5 and 4.0, the cutoff size was MW=100-300 kDa; the DRs were about 28%: and the AMWs were both about 200 kDa. For HpH 3.0, the cutoff size was MW=50-100; the DR was 29.0%; and the AMW was 73 kDa. For HpH values below 2.0, the MW cutoff size with the highest DRs was MW<50 kDa, and all of the AMWs were below 28 kDa.

• 한국수산과학회지
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• 제40권4호
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• pp.187-192
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• 2007

To prepare oligouronic acids from high-molecular-weight alginates prepared from sea tangle (Laminaria japonica), the alginates were hydrolyzed at various temperatures for 1 hr at pH 5.0. The effects of hydrolysis temperature $(H_{Temp})$ on the average molecular weight (AMW) and distribution ratio of MW (DR) in the hydrolyzed alginates were investigated. As $(H_{Temp})$ increased, the AMW of the alginates decreased exponentially; in addition the DR of the alginates with MW>500 kDa decreased exponentially, while the DR of those with MW=50-100 and MW<50 kDa increased exponentially. For the alginates with MW=300-500 and MW=100-300 kDa the DR increased exponentially until $H_{Temp}$ reached $80^{\circ}C$, and then decreased exponentially at above $80^{\circ}C$. AS $H_{Temp}$ increased, the MW cutoff size and AMW Of the alginates fraction With the highest DR both decreased. For $H_{Temp}<60^{\circ}C$, the MW cutoff size with the highest DR was MW>500 kDa; the DR was 39-67% and the AMW 1,000-1,300 kDa. For $H_{Temp}$ $80^{\circ}C$, the MW cutoff size with the highest DR was MW=300-500 kDa and the DR was about 33% and the AMW about 400 kDa. For $H_{Temp}\;100-121^{\circ}C$, the MW cutoff size with the highest DRs was MW=50-100 kDa, with a DR of 39-44% and an AMW of 70-80 kDa.

• Journal of the Korean Wood Science and Technology
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• 제49권1호
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• pp.1-13
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• 2021

This study was conducted to investigate the effects of the synthesis method, melamine content, and GPC parameters (such as flow rate, column-detector temperature, and sample injection temperature) on the molecular weight of melamine-urea-formaldehyde (MUF) resins. Two different synthesis methods were employed. In the first method, MUF-A resins were synthesized by simultaneously reacting urea, formaldehyde, and melamine (5%, 10%, and 20%) using the reaction of alkaline-acid-alkaline steps under controlled temperature and viscosity. In the second method, MUF-B resins were synthesized by first reacting melamine at the same levels with formaldehyde and then by adding urea. The highest weight average molecular weight (Mw) of MUF-A resins was found at 10% melamine content when the flow rate was 0.3 and 0.8 ml/min; Mw decreased slightly at 20% melamine content. The results showed that Mw increased with an increase in the melamine content when the flow rate was 0.5 and 1.0 ml/min. In addition, Mw was the highest when the flow rate, column-detector temperature, and injection temperature were 0.3 ml/min, 50℃, and 25℃, respectively. On the contrary, MUF-B resins had greater Mw and number average molecular weight (Mn) than MUF-A resins. Overall, Mw and Mn increased as the melamine content increased. The optimal GPC parameter for MUF resins was determined as follows: a flow rate of 0.5 ml/min, a column-detector temperature of 50℃, and a sample injection temperature of 50℃.

• Journal of the Korean Wood Science and Technology
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• 제44권6호
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• pp.913-922
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• 2016

This study attempted to measure molecular weight (MW) of melamine-urea-formaldehyde (MUF) resins prepared by two different synthesis methods: the one-step MUF resins were synthesized in one batch procedure, while the two-step MUF resins were prepared by a physical mixing of urea-formaldehyde (UF) resin with melamine-formaldehyde (MF) resin that had been synthesized in a separate procedure. The properties of medium density fiberboard (MDF) panels bonded with two types of MUF resins were also investigated. MWs of these MUF resins were measured using gel permeation chromatography (GPC). In addition, this study measured the MWs of one-step MUF resin during its synthesis procedure. The performance of two types of MUF resins was evaluated by determining properties of MDF panels prepared in laboratory. As the synthesis procedure progressed, both number average MW ($M_n$) and weight average MW ($M_w$) of one-step MUF resin gradually increased, while the polydispersity index (PDI) decreased. And low Mw species of the resin predominantly decreased as the synthesis step progressed. The one-step MUF resin showed greater $M_n$ and $M_w$ than those of the two-step ones even though the PDI values of both resins were very similar each other. As expected, the one-step MUF resin resulted in better properties of MDF panels than those of two-step resins. In particular, the one-step MUF resin provided better internal bond (IB) strength and thickness swelling (TS) with MDF panels than those of two-step ones, indicating better water resistance of the one-step resin. These results suggest that the preparation method of MUF resins have a great impact on the MW and final panel properties.

• 상하수도학회지
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• 제22권1호
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• pp.31-38
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• 2008

The primary objective of this study was to evaluate the variation of the molecular size distribution by granular activated carbon (GAC) adsorption. GAC adsorption was assessed by using the rapid small-scale column test (RSSCT) and high-performance size-exclusion chromatography (HPSEC) was used to analyze the molecular size distribution (MSD) in the effluent of GAC column. RSSCT study suggested that GAC adsorption exhibited excellent interrelationship between dissolved organic carbon (DOC) breakthrough and MSD as function of bed volumes passed. After GAC treatment, the nonadsorbable fraction which was about 25percents of influent DOC corresponded to the hydrophilic (HPI) natural organic carbon (NOM) of NOM fractions and was composed entirely of <300 molecular weight (MW) in the HPSEC at the initial stage of the RSSCT operation. The dominant MW fraction in the source water was 1,000~5,000daltons. At the bed volumes 2,500, MW <500 of GAC treated water was risen rather than it of source water. After the bed volumes 7,300 of operation, the MW 1,000~3,000 fraction was closed to about 80percents of DOC found in the GAC influent. The Number-average molecular weight (Mn) value determined using HPSEC for the effluent of GAC column was gently increased as DOC breakthrough progress. The quotient p(Mw/Mn) can be used to estimate the degree of polydispersity was shown greatest value for the GAC effluent at the initial stage of the RSSCT operation.

• 한국식품저장유통학회지
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• 제11권4호
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• pp.496-502
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• 2004

도토리 가루를 알칼리로 침전시키면서 정제하여 도토리 전분을 얻었다. 다시 이 starch를 부탄올 개량법으로 분획하여 도토리 amylose와 amylopectin을 얻었고 Corn starch와 corn amylose, corn amylopectin은 시판되는 시약을 사용하였다. 이 시료들의 분자량 분포도를 관찰하기 위하여 GCP측정을 하였다. GCP측정은 DMSO와 DMF의 용매사용과 표준물질로 pullulan을 사용하여 검정하고 각 시료들의 지연시간으로부터 행하여졌다. 분자량분포도로부터 수평균분자량 (Mn)과 중량평균분자량(Mw) 및 다 분산도를 얻었다. 그 결과 acorn amylose와 corn amylose의 중량평균 분자량이 amylopectin에 비해서 뚜렷이 작게 나타나 ${\alpha}-1,4$ 선형결합을 갖는 amylose와 ${\alpha}-1,4$ 선형결합에 ${\alpha}-1,6$ 결합가지가 있는 amylopectin의 구조상의 차이를 확인할 수 있었다. 또한 분획한 acorn과 시판되는 corn과의 분자량분포도 측정을 비교한 결과 같은 경향을 나타내어 도토리 전분의 분획이 잘 이루어졌음을 확인하였다. 다분산도는 acorn starch와 corn starch 모두 amylose와 amylopectin에 비해 크게 나타났으며 이는 전분이 분획되기전 두 성분의 불균일성에 의한 성질로 분자량분포 범위가 넓게 나타났음을 알 수 있었다. 또한, 전단속도와 온도에 따르는 점도를 관찰하였더니 전단속도가 증가하면 점도는 감소하는 현상을 나타내는 pseudo plastic power law fluid 거동(13)을 보였으며 온도가 증가하면 점도는 지수 함수적으로 감소하였다.

• 한국잠사곤충학회지
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• 제41권3호
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• pp.211-215
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• 1999

The pure-separation of calcium chloride-treated fibroin hydrolysates could be carried out using gel filtration chromatography. Also, the effect of its enzymatic hydrolysis was investigated in order to find out the enhancement of their functionality. The average molecular weight(Mw), solubility and free amino acid compositions of three hydrolysates samples (calcium chloride, calcium chloride-flavourzyme and calcium chloride-thermoase)were measured to compare their characteristics. The molecular weight of calcium chloride hydrolysate was about Mw 46,800 and it can be reduced to Mw 12,500 and 1,070 upon the enzymatic hydrolysis by flavourzyme and thermoase, repectively. A solubility of calcium chloride-treated samples shows about 60% while calcium chloride/enzyme-treated samples are perfectly soluble (100% solubility). The total amino acid composition of calcium chloride enzymatic hydrolysates are much higher than that of calcium chloride hydrolysate.

• Preventive Nutrition and Food Science
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• 제3권1호
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• pp.27-35
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• 1998

Starch-polyethylene films containing high molecular weight(NW) oxidized-polyethylene and prooxidant were prepared , and thermal -and bio-degradability of the films were determined. Increased levels of starch resulted in a corresponding reduction in mechanical strength of the films. However, the addition of high MW oxidized-polyethylene did not significantly reduce the percent elongation of the films. Thefilms containing high MW oxidized-polyethylene andproosicant were degreaded faster than those containing no aadditive during the heat treatment. The films lost their measureable mechanical properties when their weight-average MW(Mw) fell below 50,000. Biodegradability of the films was determined by a pure culture assay with either Streptomyces badius 252.S. setonii 75Vi2 or S. viridosporous T7A, and by an extracellulr enzyme assay using S. setonii 75vi2. The results from pure culture assay indicated that biomass accumulation on the film surface inhibited chemical and biological degradation of the films. The extracellular enzyme assay demonstrated decrease of percent elongation and increase of carbonyl index of the films. Therefore, extracellular enzyme assay could be used as a good method to evaluate biodegradability of the films.

• 분석과학
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• 제12권4호
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• pp.306-311
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• 1999

몇 가지 용해조건에 따른 견 단백절의 조성 변화를 SDS-polyacrylamide 전기영동법, Gel Permeation Chromatography(GPC)법 및 유리아미노산 분석을 통하여 연구하였다. 분자량의 변화에 있어 염산을 이용한 가수분해법의 경우, SDS-PAGE 방법으로는 분자량의 분포를 확인할 수 없었다. 그러나 2N-HCl, 1N-HCl, 0.5N-HCl (3시간 $110^{\circ}C$)와 중성염($CaCl_2$) 및 중성염-효소로 가수분해시킨 견 피브로인 단백질의 평균 분자량 분포는 GPC법에 의하여 각각 Mw 800, 1,500, 3,700과 46,800, 12,500으로 확인되었다. 또한 용해 조건에 의한 유리아미노산 함량은 염산의 농도가 높을수록, 효소를 사용함으로써 유리아미노산의 조성이 증가함을 알 수 있었다.