• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.12 no.1
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• pp.1-10
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• 1999

In this paper, we have investigated the effects of the environmental factors on Low Molecular Weight (LMW) silicone fluid contents existing in high temperature vulcanized (HTV) silicone rubber sample, using dipping method and contact angle, current measurement. Artificial treatments such as immersion in water, elevated temperature, UV irradiation and dry band arcing under salt-fog condition are selected as the environmental factors. This results will be helpful to investigate the degradation with time and to expect a life time, because the LMW silicone content, which is important to recovery the hydrophobicity of silicone rubber surface, show different results by each environmental factors.

• Bulletin of the Korean Chemical Society
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• v.21 no.1
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• pp.69-74
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• 2000

Applicability of Thermal field flow fractionation (ThFFF) was investigated for the analysis of masticated natural rubber (NR) adhesives produced bya hot melt mastication process. An optimum ThFFF condition for NR analysis was found by using tetrahydrofuran (THF) as a solvent/carrier and a field-programming. Low flowrate (0.3 mL/min) was used to avoid stopping the flow for the sample relaxation. Measured molecular weight distribution was used to monitor degradation of rubber during the mastication process. Rubber samples collected at three different stages of the mastication process and were analyzed by ThFFF. It was found that in an anaerobic process rubber degradation occurs at the resin-mixing (compounding) zone as well as in the initial break-down zone, while in an aerobic process most of degradation occurs at the initial breakdown zone. It was also found that E-beam radiation on NR causes a slight increase in the NR molecular weight due to the formation of a branched structure.

• Textile Coloration and Finishing
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• v.31 no.2
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• pp.98-106
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• 2019

The dyeability and fastness properties of super-hydrophobic navy dyes having different length of alkyl groups were investigated on ultra high molecular weight polyethylene fabrics. Those dyes exhibited strong color strength in the wavelength of mainly 550~650nm, which meant that they were navy color. From the results accomplished under various dyeing conditions, it can be concluded that those dyes have higher affinity on the fibers at $130^{\circ}C$ than at the lower dyeing temperature. Considering processing time and thermal damage of the fibers, one hour is good enough to obtain full strength of color. Maximum color strength was obtained at 2~3%owf of pure dyes. Except for the rub fastness under dry condition, all fastness such as to washing and light showed as good as of 4~5 ratings.

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.45-50
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• 2000

For the maximum production of pullulan from glucose as a carbon source, the effects of glucose concentration, pH and dissolved oxygen concentration on the cell growth and mass production of high-molecular weight pullulan by A. pullulans ATCC 42023 were evaluated. A. pullulans showed optimum pullulan productivity when glucose concentration was 0.3M (54g/L). And inhibitory effects on the cell growth and the pullulan production were observed at the glucose concentration higher than 0.3M (54g/L). The influence of pH control and dissolved oxygen on the pullulan production and growth of A. pullulans was studied. In shake-flasks, maximum pullulan production was obtained with $11.98g/{\ell}$ when initial pH was 6.5. In the batch fermentation, the maximum pullulan production of $13.31g/{\ell}$ was obtained with constant pH 4.5. And it was found that pullulan yield and synthesis rate increased with oxygen availability. For the production of commercially useful pullulan with high-molecular weight, a mixed carbon source, which was a mixture of glucose and glucosamine, was used for the pullulan fermentation with A. pullulans. On the basis of 5% mixed carbon source, culture with 3% glucosamine with 2% glucose was optimum condition for the production of high (M.W.> 1,000,000) and medium (M.W.> 200,000) molecular weight pullulan with considerable yields of cell mass and product. And the influence of pH control on the molecular weight of pullulan was studied in batch fermentation. It was found that the productivity of high-molecular weight pullulan with pH control at 6.5 was higher than that with no pH control.

• Advances in materials Research
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• v.3 no.2
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• pp.117-128
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• 2014

Processable conducting polyaniline derivative with free amine functional groups was successfully synthesized from the monomer o-phenylenediamine in aqueous hydrochloric acid medium using ammonium persulfate as an oxidative initiator. The synthesized poly(o-phenylenediamine) (PoPD) in critical condition was found to be completely soluble in common organic solvents like dimethyl sulfoxide, N,N-dimethyl formamide etc. From the intrinsic viscosity measurement, the optimum condition for the polymerization was established. The polymer was characterized by ultraviolet visible spectroscopy, Fourier transform infrared spectroscopy, proton magnetic resonance spectroscopy ($^1HNMR$) and thermogravimetric (TGA) analyses. The weight average molecular weights of the synthesized polymers were determined by the dynamic light scattering (DLS) method. From the spectroscopic analysis the structure was found to resemble that of polyaniline derivative with free amine functional groups attached to ortho/meta position in the phenyl ring. However, very little ladder unit was also present with in the polymer chain. The moderate thermal stability of the synthesized polymer could be found from the TGA analysis. The average DC conductivity of $2.8{\times}10^{-4}S/cm$ was observed for the synthesized polymer pellet after doping with hydrochloric acid.

• YAKHAK HOEJI
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• v.32 no.1
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• pp.86-94
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• 1988

Some rheological properties of subfractions for dextran in the molecular weights range from $3{\times}10^4$ to $2{\times}10^6$ was investigated at room temperature. The dependence of the viscosity on concentration, shear rate, pH & ionic strength, temperature and solvent effect was observed. From the experimental data the Mark-Houwink viscosity equation in water at $25^{\circ}C$ was determined for samples having the molecular weight ranging from $3{\times}10^4$ to $2{\times}10^6$ as$[{\eta}]=3.1{\times}10^{-3}\;Mw^{0.39}(in\;dl/g)$. The intrinsic stiffness of the dextran backbone was estimated by evaluating the 'characteristic ratio' $C_{\infty}$, which is below the 0.082. In the concentrated region, the viscosity was decreased with increasing shear rate and was exponentially decreased with raising temperature, the viscosity showed the maximum value at neutral condition. From the experimental data, it was concluded that dextran chain, linked by the ${\alpha}-1$, 6-glucosidic linkage, behaves like a flexible random coil chain in aqueous solution, dextran solutions were pseudoplastic power law fluids among the empirical models of non-Newtonian behavior. Urea was an active reagent which increases the viscosity and swells dextran while pyrididine and glycerol were inactive reagents. Also, it could be estimated that the formation of gel structure is promote to the neutral state, the molecular weight larger than $2{\times}10^5$, when electrolytic concentration is IN and Ureas is use to solvent.

• Journal of the Korean Graphic Arts Communication Society
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• v.18 no.1
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• pp.121-139
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• 2000

This study is to test the possibility of applying the low-molecular weighted waste cellulase, which is produced in the process of cellulase production, to paper making. After experimenting on high-crystallized non-wood fibers with beating catalyst. I got the result that the condition for the optimal effect is temperature 40~6$0^{\circ}C$, the time 90min to 120min, pH 5.0 to 6.0, the enzyme contents 0.3% and that the effect of beating such as slight reduction of fiver viscosity, increase of water retention value(WRV) and shortening of fiber length was increased with waste cellulase. Through this process, the density, folding endurance, tensile strength and burst strength of paper was remarkably increased, which is inferred to result from the increased flexibility of fiber by individual characteristics of non-wood fiber, which was high-crystallized by penetrated low-molecular weight cellulases in the fiber.

• Analytical Science and Technology
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• v.12 no.4
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• pp.306-311
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• 1999

Changes of silk protein compositions of average molecular weight (Mw) and free amino acid composition to different solubility conditions were studied by SDS-polyacrylamide electropholesis, gel permeation chromatography (GPC), and free amino acid analysis method. We can not detected average molecular weight distribution of different hydrochloric acid (HCl) conditions as SDS-polyacrylamide method, but as using GPC method, molecular weight distribution of 2N-HCl, 1N-HCl and 0.5N-HCl (3 hrs at $110^{\circ}C$ treated) are confirmed Mw 800, 1,500 and 3,700, respectively. The average molecular weight of calcium chroride and calcium chloride-enzyme treated samples are shown Mw 46,800 and 12,500, respectively. The degree of hydrolysis and the composition of the free amino acid in the fibroin hydrolysates effected significantly composition of free amino acids of the fibroin powder. The increase of the degree of hydrolysis and ratio of free amino acids and oligopeptides were found to be directly related to the concentration of hydrochloric acid and treatment of enzyme, resulting in the increase of water solubility.

• Food Engineering Progress
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• v.13 no.3
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• pp.169-175
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• 2009

Water soluble polysaccharides (WSP) and arabinogalactan of Portulaca oleracea L. (POL) were increased after extrusion and commercial cellulase treatment. Arabinose and galactose content increased more about 1.5 times than those of raw POL, and rhamnose also increased about 2.6 times in WSP. High molecular weight fraction (I) of POL depending on extrusion condition including Ext I, Ext II and Ext III degraded into low molecular weight fraction (II) about 37, 29, and 26%, respectively, ranged from 67,000-69,000 Da of molecular weight. Especially, the molecular weight and composition of WSP with extruded, were increased from 9 to 13% in low molecular weight fraction, compared to those of raw POL. Solubilization and degradation of polysaccharides were a directly propotional to specific mechanical energy in POL extrusion. WSP obtained by extrusion at Ext I and Ext II were found to be effective antioxidants in different in vitro assays with regards to 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and Trolox equivalent antioxidant capacity (TEAC). However, these results suggest that WSP obtained using extrusion and subsequent enzymatic treatment may be an effective method to produce arabinogalactan from POL and be used as a functional food ingredients.

• Journal of Conservation Science
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• v.37 no.5
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• pp.557-566
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• 2021

We investigated the properties of Korean traditional animal glue which are associated with the use of different parts of cattle hide and extraction conditions. Both average molecular weight(Mw, Mz) and polydispersity (PDI) of the animal glue increased with extraction time, whereas only PDI decreased after 48h. There were no differences in the average molecular weight and PDI for the different cattle hide parts used, although a individual difference was observed with regard to total molecular weight. Differences in extracts over time were compared by investigating the amide regions representing the gelatien component of the animal glue. The triple helix structure of the belly skin deteriorated in a manner proportional to the extraction time, and differences were observed for each cattle hide part. The yellowness increased with the extraction time; however, the viscosity was not proportional to the average change in molecular weight. This study has some limitations because of difficulties in the quality control of cases where small amounts of glue were extracted as small differences might impact the overall results considerably. Further research exploring various extraction conditions is required to ensure the prodiction of traditional animal glue with optimum qualities.