• Journal of Microbiology and Biotechnology
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• v.11 no.2
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• pp.342-345
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• 2001

A bacterial strain PH-4, which produces an enzyme catalyzing the degradation of crosslinked poly(${\gamma}$-glutamic acid) hydrogels, was isolated and identified as a Flavobacterium sp. The enzyme was obtained by the sonication of the bacterial cells preincubated in a Bouillon medium with shaking, without adding of poly(${\gamma}$-glutamic acid) as an inducer. The products of the hydrogel degraded by the crude enzyme agreed closely with the depolymerized materials in SDS-polyacrylamide gel electrophoresis using methylene blue staining, and with a glutamic acid monomer on thin-layer chromatography, thereby suggesting that strain PH-4 produced a kind of exohydrolase.

• Proceedings of the Materials Research Society of Korea Conference
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• 2011.05a
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• pp.54.2-54.2
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• 2011

DTBP (dimethyl 3,3`-dithiobispropionimidate) was applied to collagen and gelatin coating on BCP granules and a crosslinking agent. The DTBP crosslinking was done for decreasing the solubility of the coating and hence increasing the stability. The nanostructure of collagen and gelatin coating surfaces were observed by SEM technique. Based on the DSC thermograms and FT-IR spectrums, the crosslinkings were confirmed between collagen molecules and gelatin molecules. The compressive strength was measured before crosslinking and after that. In-vitro study was carried out by measuring cell viability and observing cell morphology after DTBP crosslinking. Moreover, the proliferation ability of MG-63 osteoblast-like cells on the crosslinked BCP granules was evaluated by Western blot assay. The BCP granules were implanted into rabbit femur for 4 weeks and 12 weeks. The bone tissue formation was analyzed with micro-computed tomography (micro-CT) and histological analysis was also carried out by hematoxylin and eosin (H&E) staining for visualization of cells.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.356-356
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• 2006

The use of renewable feedstock is an important issue to reduce the fossil fuel consumption. In this contribution, we report the cationic ring-opening polymerization of a 2-oxazoline monomer with soybean fatty acid side chains (SoyOx) under microwave irradiation. Kinetic experiments were performed to investigate the livingness of the polymerization in both acetonitrile and in the absence of solvent. In addition, both block and statistical copolymers were prepared using the SoyOx monomer. The synthesized (co)polymers were crosslinked under UV-irradiation resulting in insoluble polymeric materials and core-crosslinked micelles.

• Proceedings of the Membrane Society of Korea Conference
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• 1996.10a
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• pp.86-87
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• 1996

IPN (Interpenetrating Polymer Network) is a mixture of two or more crosslinked polymers with physically interlocked network structures between the component polymers. IPN can be classified as an alloy of thermosets and has the characteristics of thermosets such as the thermal resistance and chemical resistance and also has the characteristics of polymer alloys with enhanced impact resistance and amphoteric properties. The physical interlocking during the synthesis restricts the phase separation of the component polymer with chemical pinning process, thus the control of morphology is possible through variations of the reaction temperature and pressure, catalyst concentration and crosslinking agent concentration. Finely dispersed domain structure can be obtained through IPN synthesis of polymer components with gross immiscibility. In membrane applications, particularly for the separation of liquid mixtures, crosslinked polymer component with specific affinity to the permeate is needed. With the presence of the permeant-inert polymer component, the mechanical strength and the selectivity of the membranes are enhanced by restricting the swelling of the transporting polymer component networks.

• Korea-Australia Rheology Journal
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• v.11 no.4
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• pp.293-304
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• 1999

Refinements of classical theories for entangled or crosslinked polymeric systems have led to incommensurable models for rubber networks and polymer melts, contrary to experimental evidence, which suggests a great deal of similarity. Uniaxial elongation and compression data of linear and branched polymer melts as well as of crosslinked rubbers were analyzed with respect to their nonlinear strain measure. This was found to be the result of two contributions: (1) affine orientation of network strands, and (2) isotropic strand extension. Network strand extension is caused by an increasing restriction of lateral movement of polymer chains due to deformation, and is modelled by a molecular stress function which in the tube concept of Doi and Edwards is the inverse of the relative tube diameter. Up to moderate strains, $f^2$ is found to be linear in the average stretch for melts as well as for rubbers, which corresponds to a constant tube volume. At large strains, rubbers show maximum extensibility, while melts show maximum molecular tension. This maximum value of the molecular stress function governs the ultimate magnitude of the strain-hardening effect of linear and long-chain branched polymer melts in extensional flows.

• Fibers and Polymers
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• v.2 no.4
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• pp.184-189
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• 2001

Continuous photografting/crosslinking of polyethyleneglycol dimethacrylate oligomers onto cotton using a water-soluble benzophenone photoinitiator was investigated. Photografting increased with increasing irradiation dose, oligomer concentration and photoinitiator concentration. Maximum grafting efficiency of DM 400 and 600 were 83% and 79%, respectively. the photografting increased the wrinkle resistance of cotton implying surface crosslinking of cotton. bothsurface crosslinking and bulk crosslinking of cotton were accomplished via dual curing of a mixed formulation containing both a thermally curable component (BTCCA/SHP) and a UV-curable component. The wrinkle resistance of the crosslinked cotton was found to be higher when cured by thermal curing due to the facile post-polymerization of the UV active component. The presence of crosslinks in the dually crosslinked cotton was verified with FT-IR and thermogravimetric analysis.

• Textile Coloration and Finishing
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• v.22 no.3
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• pp.214-219
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• 2010

Polyethylene(PE) films were photocrosslinked by continuous UV irradiation. Benzophenone addition as low as 1wt% into the PE film increased the gel fraction up to 96%. The photocrosslinking was attributed to the recombination of PE radicals generated upon UV irradiation, which was enhanced by the hydrogen abstraction of the added benzophenone. Also the crossliked PE showed higher thermal stability and decreased crystallinity with increasing UV energy as shown by TGA, XRD and DSC analysis. It was also possible to fix 5.4% octadecane into PE by the photocrosslinking. The crosslinked PE film containing octadecane showed lower tensile strength and modulus coupled with higher extension compared to that without octadecane, which can be used as a new plasticizing method for the crosslinked PE film.

• Applied Chemistry for Engineering
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• v.4 no.2
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• pp.416-422
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• 1993

In order to prepare high performance polymeric membrane, the crosslinked chitosan(C. Chitosan)membrane was prepared, the transport and the selective separation of the metal ions through the membrane were investigated. It was observed that the transport rates of the metal ions through the membrane increased according to the decreasing of the initial pH in downstream solution. Proton pump mechanism for this transport phenomenon was suggested. The transport selectivity is dependent on the selective adsorption resulting from the complex formation of chitosan with each metal ion. The separatin factor(${\alpha}_{Cu}{^{2+}}$) for the membrane was 9.5.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.49 no.8
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• pp.455-461
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• 2000

The inhibiting effects of electrical treeing and insulation properties of LDPE contained with treeing inhibitors was studied under radiation environment. Barbituric acid and its derivatives were selected as treeing inhibitors. The inception voltage and growth of tree, AC breakdown strength, volume resistivity, high frequency capacitance, and dissipation factor were observed as a function of dose(up to 1000 kGy). And also, measurements of thermo-luminescence(TL), and gel content were carried out. Crosslinked low density polyethylene(XLPE) contained with treeing inhibitors shows better insulation characteristics such as electrical tree propagation, AC breakdown strength, and volume resistivity than those of pure LDPE. The most effective treeing inhibitor was found on the barbituric acid contained XLPE.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.2
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• pp.127-132
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• 2002

Space charge distributions and behaviors in silane crosslinked polyethylene(SXLPE)/ crosslinked polyethylene(XLPE) laminates were investigated using a pulsed electroacoustic (PEA) method. In case of monolayer, XLPE shows heterocharge while SXLPE shows homocharge. It was observed that charges were accumulated at the interface of SXLPE/XLPE laminate when applied electric field was more than 20kV/mm. The charge profile at various temperatures was also acquired using temperature-controllable PEA system. Although applied electric field is only 8.6 kV.mm, positive interfacial charge starts to appear near 50$^{\circ}C$. It was found that the interfacial charge behavior of SXLPE/XLPE laminate under low voltage at high temperature is corresponding to that under high voltage at room temperature.