• Elastomers and Composites
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• 제34권4호
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• pp.285-291
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• 1999

Effects of catalysts on network structure, hard segment length and distribution of polyurethane foams in the absence of catalysts were investigated. CFC free all MDI-based poly urethane foams were prepared from poly(ethylene adipate)glycol, 4,4'-diphenylmethane diisocyanate, and water. Amino catalysts used were 1,4-diazabicyclo[2,2,2]octane(DABCO), N, N,N',N'-tetramethyl--hexane-1,6-diamine(MR), bis(2-methylamino ethyl)ether(ET), 1,8-diazabicyclo-[5,4,0]-undecene-7(DBU). Dibutyltindilaurate(DBTL) as control was also used. Hard segment components of polyurethane foams were obtained by a selective degradation of polyester chains with 0.01N KOH-methanol solution. The PUFs with DBU catalyst contained more amount of isocyanurate components than other PUFs. On the other hand, the PUFs with ET, MR, DBTL catalysts contained more amount of allophanate and biuret component than the other PUFs.

• 한국응용과학기술학회지
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• 제15권1호
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• pp.35-45
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• 1998

Chitin/chitosan be known as biodegradable natural polymer. However, commercial use of chitin has been limited due to highly resistance to chemicals and the absense of proper solvents. Therefore, we was studied that chitin was prepared by the application of Hackman's method from Protunus trituberculatus shells. And another viscosity chitosan were prepared from chitin which were deacetylated under various concentration of alkali, reaction time and temperature by the application of Mima's method. And crosslinked chitin/chitosan was preparaed from chitin/chitosan with crosslink agent followed by crosslinkage. The major parameters for chitosan manufacturing methods were found to be concentration of alkali solution, reaction time and temperature etc. The effects of these parameters on chitin, another viscosity(molecular weight) chitosan and crosslinked chitin/chitosan were investigated by various analysis apparatus.

• Bulletin of the Korean Chemical Society
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• 제19권6호
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• pp.680-685
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• 1998

Two kinds of new aliphatic diols were synthesized by the ring-opening reaction of lactide and glycolide with 1,4-butanediol, a difunctional initiator, in the presence of stannous octoate. The resulting aliphatic diols were melt-polymerized with D-tartaric acid at 150 ℃ to produce new crosslinkable polyesters. They were reacted with hexamethylene diisocyanate in THF at 65 ℃ in a teflon mold for 24 h to prepare sequentially ordered crosslinked polyesters (BD/LT/GL/D-tartarate). Degradation of the prepared yellow crosslinked films was carried out in a buffer solution in order to examine the effect of time, pH, temperature and crosslinking degree on their degradation rate and mechanism. The rate of degradation increased with an increase in pH and temperature, but it decreased with increasing degree of crosslinkage incorporated into the crosslinked polyesters. We also found that the crosslinked polymers were converted into the acidic compounds such as lactic, glycolic, and D-tartaric acids during the degradation.

• Applied Biological Chemistry
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• 제34권4호
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• pp.373-378
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• 1991

일반 농가에서 수세미 사과락의 표피 및 그물섬유중 육질 제거를 위하여 개천수에 침지하여 20여일 소요되는데 비하여, 사과락을 압착한 후 0.2% NaOH로 처리한 결과 $3{\sim}5$시간내에 처리가 가능하였다. 0.2% 알카리 용액과 계면활성제인 0.02% Monopol과 표백제인 0.1% $Ca(OCl)_2$를 처리하여 섬유소의 품질을 보호하면서 육질제거효과를 기할 수 있었다. 또한, 사용 목적에 따라 습경성과 인장강도와 같은 물리성을 formaldehyde, glutardialdehyde, glyoxal과 같은 가교제를 사용하여 조절할 수 있는 가능성을 나타냈다. 또한 산알카리 및 열적 안정도가 양호하여 목욕용 기구, 주방용 세척기구, 오일이나 까스 여과기, 기타 각종 장식용 제조 원료로 사용가능하다는 결론을 얻었다. NaOH 용액의 농도 저하와 KOH로 대치할 때 생성되는 스럿지를 K질 비료로 활용하는 방안 등이 연구중이다.

• Journal of Pharmaceutical Investigation
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• 제39권1호
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• pp.59-63
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• 2009

Soybean phosphatidylcholine microparticles loaded with cyclosporin A (CsA) were prepared by the modified emulsion solvent diffusion and ionic gelation method, in which chitosan on the surface of the microparticles was crosslinked with various concentrations of tripolyphosphate (TPP). The morphology of the particles was characterized by scanning electron microscopy (SEM). The change of particle size and zeta-potential by chitosan on the surface of the lipid microparticles were systematically observed. The encapsulation efficiency and loading capacity of CsA in the particles were determined by high performance liquid chromatography (HPLC). In vitro release kinetics was studied using the dialysis method. In the results, the mean particle size and the zeta-potential of lipid microparticles increased when the attached chitosan was cross-linked (from 2.5 to 6.2 ${\mu}m$ and from -37.0 to +93.0 mV, respectively). The cyclosporin A-loaded lipid microparticles appeared discrete and spherical particles with smooth surfaces. The encapsulation efficiency of CsA was between 79% and 90% while the loading capacity was between 41% and 56%. In vitro release study showed that the crosslinkage of chitosan by TPP significantly delayed the release of CsA from the particles in a concentration-dependent manner. Thus, the release of CsA from the lipid microparticles could be controlled by tripolyphosphate used as a cross-linking agent.

• 한국식품위생안전성학회지
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• 제13권1호
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• pp.34-40
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• 1998

수산계 폐기물로부터 chitin 유도체의 다양한 응용에도 불구하고 chitin 의 상업적 이용은 적절한 용매의 부재와 화학적 제한성으로 인하여 제한적으로 이용되었다. 그러므로 Mima의 방법을 응용하여 NaOH 농도, 반응시간, 온도 등을 조절하여 탈아세틸화반응에 의한 다양한 점도가 다른 chitosan을 제조하였으며, 2종의 각Y제를 이용하여 가교결합에 의한 결정성을 증가시킨 가교 chitosan을 제조하였따. 제조한 점도가 다른 chitosan과 가교 chitosan 유도체를 다양한 분석기기를 이용하여 측정하였다. chitosandmf 제조시 반응시간을 높이거나 반응온도를 높이면 탈아세틸화는 높아지나 분자사슬의 크기, 즉 점도와 분자량은 감소하였다. 반응온도, 반응시간과 알칼리 농도에 따라 활용분야에 맞은 chitosan을 제조할수 있다.

• Journal of Chest Surgery
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• 제32권11호
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• pp.989-997
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• 1999

Background: Calcific degeneration is the major cause of clinical failure of glutaraldehyde (GA) crosslinked bioprosthetic tissues implanted in the body and necessitates the reoperation or causes death. Surface modification of biologic tissues using sulfonated polyethyleneoixde (PEO-SO3) has been suggested to significantly enhance blood compatibility, biostability and calcification-resistance by means of the synergistic effect of highly mobile and hydrophilic PEO chains and electrical repulsion of negatively charged sulfonate groups. This study was designed to evaluate the anticalcification effect of surface-modification of biologic arteries by direct coupling of PEO-SO3 after GA fixation and changes of calcification according to the implantation period through the quantitative investigation of the deposited calcium and phosphorous contents of the biologic arterial tissues in the canine circulatory implantation model. Material and Method: Total of 16 fresh canine carotid arteries were harvested from eight adult dogs and divided in to GA group(n =8) and PEO-SO3 group(n=8). Sulfonation of diamino-terminated PEO was performed using propane sultone. Canine carotid arteries were only crosslinked with 0.65% GA solution in GA group and modified by direct coupling 5% PEO-SO3 solution after GA crosslinkage for 2 days and stabilized by NaBH4 solution for 16 hours in PEO-SO3 group. In both groups the resected segment of bilateral carotid arteries were reconstructed. Reconstructed segments of the two groups were analysed the quantities of calcium and phosphorous contents after 3(n=4) and 6(n=4) weeks in vivo. Result: After implantation of 3 seeks, PEO-SO3 group showed significantly less depositions.