• Textile Coloration and Finishing
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• v.35 no.4
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• pp.246-255
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• 2023

In this study, we investigated for natural rubber foam to replace petrochemical-based neoprene foam. Experiments were conducted on vulcanization system and 2-step foaming process of natural rubber. The vulcanization system were EV(Efficient Vulcanization Cure), Semi-EV(Semi-Efficient Vulcanization Cure) and CV(Conventional Vulcanization Cure). In the 2-step foaming process, first molding temperature was 140℃, times were 15, 20, 25, and 30minutes, and the second molding temperature was 160℃, the times 5, 10, 15, and 20minutes. The cure and viscosity characterization were evaluated by oscillating disc rheometer (ODR) and mooney viscosmeter. Various mechanical characteristics, including hardness, tensile strength, elongation at the point of rupture, and tear strength, were quantified. Subsequently, an assessment of alterations in these mechanical attributes was conducted post-immersion in a NaCl solution. In addition degree of volume change was measured after immersing the NR foam in NaCl solution and the low-temperature permanent compression set was evaluated at 4℃. And expansion ratio and shrinkage ratio of NR foam were evaluated for 28 days. As a result the EV vulcanization system showed the least change in physical properties before and after salt water immersion, and the lowest shrinkage ratio for 28 days. In addition it was confirmed that the 2-step foaming optimum condition differed depending on the appropriate vulcanization condition.

• Biotechnology and Bioprocess Engineering:BBE
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• v.7 no.1
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• pp.26-30
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• 2002

A droplet fractionation method was previously developed to concentrate a dilute nonfoaming protein solution. In that earlier study with invertase, it was demonstrated that droplets created by ultrasonic energy waves could be enriched up to 8 times that of the initial dilute invertase solution. In this study, a mixture of bromelain (a foaming protein) and invertase (a nonfoaming protein) is investigated as a preliminary step to determine if droplet fractionation can also be used to separate a non-foaming protein from foaming proteins. The foaming mixture containing bromelain is first removed by bubbling the binary mixture with air. After the foam is removed, the protein rich air-water interfacial layer is skimmed off (prior to droplet fractionation) so as not to interfere with the subsequent droplet production from the remaining bulk liquid, rich in non-foaming protein. Finally, sonic energy waves are then applied to this residual bulk liquid to recover droplets containing the non-foaming protein, presumed to be invertase. The primary control variable used in this droplet fractionation process is the pH, which ranged for separate experiments between 2 and 9. It was observed that the maximum overall protein partition coefficients of 5 and 4 were achieved at pH 2 and 4, respectively, for the initial foaming experiment followed by the post foaming droplet fractionation experiment.

• Elastomers and Composites
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• v.50 no.1
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• pp.13-17
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• 2015

A study of the effects of MWCNT as a nucleating agent on the formation reactions of the rigid polyurethane foams (RPUFs) was carried out. Sample PUFs, formulated with grease-type master batch of MWCNT/surfactant, were fabricated by free-rising method. Temperature changes with time during foaming process were measured using a digital thermometer. RPUF foaming process was observed to undergo 2-step processes with temperature inflection around 60 sec after the start of reaction, and then reached slowly the max. temperature. While the max. temperature of neat PUF was measured as ca. $120^{\circ}C$, that of the samples with MWCNT were as higher value as ca. $130^{\circ}C$, and, even the time to reach that temperature was reduced by about 15 sec. Average cell size of PUF samples decreased from 185.1 for the neat PUF to $162.9{\mu}m$ for the sample of 0.01 phr of MWCNT. As the result, it was considered that MWCNT in RPUF foaming process could play a roll both as a nucleating agent and as a catalyst.

• Proceedings of the KAIS Fall Conference
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• 2008.11a
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• pp.335-338
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• 2008

2단발포에서 금형시간이 천연고무(NR) 스폰지의 팽윤에 미치는 효과를 검토하였다. Kneader와 Rollmill을 사용하여 NR컴파운드를 제조하고 높은 압력조건의 1차금형에서 부분가교시킨 후 대기압의 2차 금형에서 발포와 가교를 완성시켰다. NR스폰지의 겉보기밀도를 측정하고 주사전자현미경을 사용하여 셀구조를 관찰하였다. 얻어진 스폰지에 대하여 실온에서 톨루엔, 이소옥탄, 항공유에 의한 팽윤거동을 조사하였다. 1차금형시간이 증가하면 NR스폰지의 겉보기밀도가 증가하고 팽윤비가 감소하였다. 2차금형시간이 증가하면 NR스폰지의 겉보기밀도가 감소하고 팽윤비가 증가하였다. 용매의 접촉에 의한 NR 스폰지의 부피팽윤비를 높이기 위하여 금형에서 동시에 발생하는 발포제의 분해반응과 NR의 가교반응을 적절히 조절하는 것이 중요하다.

• Applied Biological Chemistry
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• v.37 no.2
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• pp.85-93
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• 1994

The fish skin gelatin hydrolysates were produced using a continuous two-stage membrane (MWCO 10,000, MWCO 5,000) reactor, and molecular weights, amino acids and functional properties of the hydrolysates were investigated. The major molecular weights distribution of the major fractions were $8{\sim}10\;KDa$ and $4.5{\sim}6.5\;KDa$ in the 1st-step hydrolysates, $2{\sim}6\;KDa$ and $0.5{\sim}2\;KDa$ in the 2nd-step hydrolysates. Among the amino acids in the hydrolysates, glycine, proline, serine, alanine, hydroxyproline, glutamic acid and aspartic acid having sweet taste were responsible for $68{\sim}72%$ of the total amino acids. But valine, methionine, isoleucine, leucine, phenylalanine and histidine having a bitter taste were only $23{\sim}25%$ Taste evaluations show that the gelatin hydrolysates have a brothy and sweet taste, 2nd-step hydrolysate have more a favorable taste than 1st-step hydrolysate. The hydrolysates were completely soluble and clear over the entire pH range. Moisture sorption at intermediate water activities of the 2nd-step hydrolysate was much higher than the unmodified fish skin gelatin, but foaming and emulsification properties were poor. Buffer capacity of the 2nd-step hydrolysate was higher than the fish skin gelatin and 1st-step hydrolysate, while viscosities of the hydrolysates were lower than the fish skin gelatin.