• International Journal of Industrial Entomology and Biomaterials
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• v.45 no.1
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• pp.12-16
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• 2022

Di-tyrosine photo-crosslinking of silk fibroin (SF) is recently highlighted as a biocompatible hydrogel fabrication process, because this method does not need potentially harmful chemical species. However, the resulting crosslinking density is often insufficient to obtain a mechanically stiff hydrogel unless additional oxygen is provided during the reaction. In this study, we proposed a combinational crosslinking method to form an SF hydrogel via the di-tyrosine photo-crosslinking with riboflavin (photoinitiator) and physical interaction of SF chains. In the UV light-irradiated SF solution, small particles formed and these particles promoted β-sheet formation of SF molecules, resulting in quick gelation. The di-tyrosine photo-crosslinking produced nuclei that might trigger regular assembly of SF molecules in high temperature condition. Conclusively, this process would contribute to a development of biocompatible hydrogel fabrication for biomedical uses of SF hydrogels.

• Journal of Radiation Industry
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• v.5 no.2
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• pp.107-112
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• 2011

Electron beam-induced crosslinking of polycaprolactone (PCL) films containing various crosslinking agents (CAs) was investigated in this study. PCL films containing various CAs prepared by a solution casting method were irradiated by electron beams at various absorption doses and the irradiated PCL films were investigated in terms of their crosslinking degree, thermal and mechanical properties, and biodegradability. Based on the results of the crosslinking degree measurement, triallyl isocyanurate was found to be most effective for the electron-beam induced crosslinking of PCL films. The results of the UTM, DMA, and TMA revealed that the thermal and mechanical properties of the crosslinked PCL films were greatly improved in comparison to those of the pure PCL. The results of the enzymatic degradation test revealed that the biodegradability of the crosslinked PCL films was reduced in comparison to that of the pure PCL.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2009.11a
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• pp.15-16
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• 2009

Poly(vinyl alcohol) was crosslinked by UV irradiation in the presence of water soluble photoinitiators. The crosslinking of PVA films with 1,2,3,4-Butanetetracarboxylic acid(BTCA) and sodium phosphinate monohydrate(SPM) was also achieved via thermal curing. Different factors in the crosslinking including thermal and radiation methods were studied. Gel fraction of PVA films increased with increasing photoinitiator concentration. The maximum gel fraction on the crosslinking method was reached about 81%. The glass transition and maximum decomposition temperature improved by both thermal and radiation crosslinking.

• Journal of the Korean Ceramic Society
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• v.49 no.6
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• pp.518-522
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• 2012

Hyaluronic acid (HA) microbeads were synthesized by dropping 0.5 wt% of sodium hyaluronate dissolved in NaOH into 0.2 vol% of divinyl sulfone dissolved in 2-methyl-1propanol at a speed of 0.005 ml/min. HA microbeads were collected from a divinyl sulfone crosslinker solution stirred at 200 to 400 rpm for 5 h at temperatures from room temperature to $60^{\circ}C$ at intervals of $10^{\circ}C$. The crosslinked microbeads were then cleaned thoroughly using distilled water and ethanol. SEM results revealed that the microbeads were white-colored spheres. The 3-D porous network structure of the microbeads became dense with an increase in the crosslinking temperature; however, no dependence of the crosslinking temperature on the microbead size was detected. The extent of swelling decreased from 970% to 670% with an increase in the crosslinking temperature from room temperature to $60^{\circ}C$, most likely due to the increase in the degree of crosslinking.

• Journal of the Korean Applied Science and Technology
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• v.38 no.1
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• pp.300-308
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• 2021

In this study, 3D networked poly(sodium acrylate) gel was polymerized and controlled with the crosslinking environment to evaluate the mechanical properties and swelling behavior. In general, as the degree of crosslinking in a pre-gelled solution increases, the swelling ratio of the 3D networked gel decrease while the mechanical strength of the gel increases. Interestingly, this study demonstrates that the polymerization and crosslinking efficiency in gelling process could be depended on the crosslinking environment by evaluating the number of elastically cross-links in 3D networked gel. As a result, the number of elastically corss-links would be changed with 3.6 times as varying of the crosslinking environment while keeping the degree of crosslinking. It is expected that the 3D networked gel would be optimized as an effective absorbing agent for VOCs by using the gel evaluation method based on the number of elastically cross-links.

• Applied Chemistry for Engineering
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• v.5 no.6
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• pp.1036-1043
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• 1994

The silane crosslinking method was applied for the crosslinking of polyethylene (PE). Crosslinking of PE was performed by, first grafting vinyltrimethoxysilane(VTMOS) to the main chain of PE using an extruder at $200{\sim}210^{\circ}C$, followed by exposure to three different silane crosslinking conditions (1. immersed in $80^{\circ}C$ water, 2. at $80^{\circ}C$ air forced convection oven, 3. exposed to air at room temperature ). The thermal characteristic changes of PE resins with respect to the silane crosslinking conditions were studied by measuring the crystalline melting temperature, density and crosslinking reaction rate. Because silane crosslinking was carried out at solid state, crystalline melting temperature, crystallinity, crystal growth rate, crosslinking reaction rate and the change in the density of silane crosslinked PE were affected by crosslinking condition and the type of base resin. The properties of silane crosslinked PE were different from those of Peroxide crosslinked PE which was crosslinked at the molten state. It was found, from the result of DSC analysis, that silane crosslinked linear low density polyethylene(LLDPE) crosslinked at room temperature had no secondary melting peak because the crosslinking reaction proceeds slowly as the crystalline grows. After crystallization, the melting point of PE was lowered by crystalline interruption of crosslinked site.

• Nuclear Engineering and Technology
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• v.13 no.4
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• pp.245-253
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• 1981

The properties of polyethylene materials exhibit good insulation and radiation resistance, but exhibit poor flame resistance. Flame retardant properties of the polyethylene were improved by the radiation induced grafting or crosslinking. When the various flame retardants were fixed onto polyethylene, the amount of fixation in grafting was increased with the increase of radiation dosages. In the case of grafting, it is necessary for high grafting yield that the polyethylene films were swelled before irradiation with ${\gamma}$-rays or electron beams. It is the suitable method for the fixation of flame retardant that polyethylene samples were blended with various flame retardants at 1$25^{\circ}C$ and then blended polymers were crosslinked by the electron beams at room temperature.

• Journal of Radiation Industry
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• v.6 no.2
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• pp.171-176
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• 2012

In this study, a crosslinked poly(styrene-butadiene-styrene) [SBS] block copolymers were prepared by using gamma ray irradiation method. The effects of various radiation doses on the degree of crosslinking, thermo property, and morphology of crosslinked SBS block copolymer were investigated. The degree of crosslinking of crosslinked SBS block copolymers were measured by gel-fraction and FT-IR. It was found that the degree of crosslinking of crosslinked SBS block copolymers increases with increase of the irradiation dose while the TGA result shows that the initial degradation temperature of irradiated SBS block copolymer was shifted to lower temperature with increasing irradiation dose. These results indicate that degradation reaction also occurs when SBS block copolymer is exposed to gamma ray irradiation for crosslinking reaction. The SAXS and FE-SEM results indicate that the phase separation of the styrene block and butadiene block was reduced with increasing irradiation dose.

• Polymer(Korea)
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• v.35 no.1
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• pp.66-71
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• 2011

With the synthesis of hyper crosslinked polymer particle (HCPP), having microporous structure with hydroxyl functional group, synthesized via polymerization reaction consists of three stepssuspension polymerization, hyper crosslinking by Friedel-Craft catalysis and hydrolysis reaction, the effects of the ratio of each monomer, hyper crosslinking conditions and $CO_2$ supercritical drying on the variations of surface morphology, pore size & distribution and BET surface area of HCPP have been investigated. It was observed that the formation of surface crack or fracture of HCPP was intimately related with the degree of hyper crosslinking reaction between microphase separated domains. And the value of BET surface area of HCPP increased with the increase of reaction temperature, time and the amounts of solvent used in hyper crosslinking step. Moreover, $CO_2$ supercritical drying was proven to be a very effective method for removing stabilizer, unreacted monomers and oligomers from HCPP but needed to add methanol as a co-solvent for efficient removing of residual catalyst.

• Proceedings of the KIEE Conference
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• 1995.07c
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• pp.1058-1060
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• 1995

In this paper, we studied the tracking characteristics of silicone rubbers that differed in the degree of crosslinking. As the tracking method, we adopted ASTM D 2303 and Merry-Go-Round(MGR) test method. It was found that the higher the degree of crosslinking, the better tracking characteristics. In these two test methods, specimens showed similar tendency of performance variation according to the degree of crosslinking. However the degradation phenomena were very different. As for MGR method, only the color of specimens' surface changed without any erosion or tracking path on them. On the contrary, the specimens subjected to ASTM D 2303 test method showed severe erosion.