• Elastomers and Composites
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• v.33 no.5
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• pp.315-323
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• 1998

The purpose of this study was to investigate the crosslinking density and reinforcement of rubber compounds with various carbon black loadings, cure systems and cure temperatures. Bound rubber content increased with volume fraction of carbon black in rubber compounds, but total crosslinking density decreased with increasing the bound rubber content. Rate constant of cure reaction was changed significantly by cure system and cure temperature, especially it showed strong dependence on the cure temperature. High activation energys of cure reaction were shown in the rubber compound with high loading of carbon black under EC system and in the rubber compound with low loading of carbon black under CC system. High total crosslinking density of vulcanized compounds appeared in the rubber compound with low loading of carbon black and CC system among cure systems. Typical change of total crosslinking density by EC system was not shown. The highest elastic constant by Mooney-Rivlin equation was shown in the rubber compound with low loading of carbon black and SEC system. Modulus increased as increasing the loading of carbon black in the rubber compounds and showed the order of SEC, CC, and EC system for cure system.

• Proceedings of the Korean Society of Dyers and Finishers Conference
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• 2008.04a
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• pp.135-137
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• 2008

PVA films with 1,2,3,4-Butanetetracarboxylic acid(BTCA) and sodium hypophosphite monohydrate(SHM) were crosslinked via thermal curing. Different parameters affecting on the crosslinking were investigated including BTCA and SHM concentration, curing temperature and time. The cured films was extracted with boiling water and gel fraction was calculated from weight change of the PVA films. Moisture regain of the gelled films was also measured. While the gel fraction of PVA films increased with increasing curing temperature and time, moisture regain decreased. Water resistance of the crosslinked PVA films improved by the BTCA crosslinking treatment.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.793-798
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• 2003

The purpose of this study is to investigate the setting properties of polystyrene mortars using waste expanded polystyrene(EPS) solution-based binders. The binders for polystyrene mortars are made by mixing crosslinking agent with waste EPS solutions which prepared by dissolving EPS in styrene. Polystyrene mortars are prepared with various EPS concentrations of EPS solutions and crosslinking agent contents, subjected to a dry curing, and tested for working life, peak exotherm temperature and 10h-length change. From the test results, the working lives of polystyrene mortars are shortened with raising EPS concentration of EPS solution and crosslinking agent content. Low-shrinkage or non-shrinkage of polystyrene mortars should be accomplished by adjusting EPS concentration of EPS solution and crosslinking agent content.

• Elastomers and Composites
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• v.57 no.4
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• pp.222-230
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• 2022

In this study, a low-heat additive with a crosslink structure was dispersed in asphalt to simultaneously lower the production temperature of, and to modify the asphalt binder. This low-heat additive was prepared by different feeding ratios of styrene-butadiene-styrene (SBS) and polyvinylchloride (PVC) as polymer modifiers, and ZnO as a crosslinking agent. In order to confirm the crosslinking density and compatibility of the crosslink structured low-heat additive with asphalt, surface free energy, swelling ratio, differential scanning calorimetry (DSC), and scanning electron microscope (SEM) parameters were carefully investigated to examine this relationship, and the role of the crosslink structured low-heat additive. In addition, by measuring the penetration and softening point of the asphalt binder, it was confirmed that it corresponds to PG 64-22. With increasing ZnO in the crosslink structured low-heat additive, the swelling ratio decreased, leading to an increase in crosslinking density. The crosslink structured low-heat additive and the asphalt binder were found to be compatible with each other by DSC and SEM analysis.

• Macromolecular Research
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• v.14 no.3
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• pp.373-382
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• 2006

A series of crosslinkable, waterborne polyurethanes (I-WBPUs) were prepared by in-situ polymerization using isophorone diisocyanate (IPDI)/poly(tetramethylene oxide) glycol (PTMG, $M_n$=2,000)/dimethylol propionic acid (DMPA)/ethylene diamine (EDA)/triethylamine (TEA)/aminoplast[hexakis(methoxymethyl)melamine (HMMM)] as a crosslinking agent. Typical crosslinkable, waterborne polyurethanes (B-WBPUs) blended from WBPU dispersion and aqueous HMMM solution was also prepared to compare with the I-WBPUs. The crosslinking reaction between WBPU and HMMM was verified using FTIR and XPS analysis. The effect of the HMMM contents on the dynamic mechanical thermal, thermal, mechanical, and adhesion properties of the I-WBPU and B-WBPU films were investigated. The storage modulus(E'), glass transition temperatures of the soft segment ($T_{gs}$) and the amorphous regions of higher order ($T_{gh}$), melting temperature ($T_m$), integral procedural decomposition temperature (IPDT), residual weight, $T_{10%}$ and $T_{50%}$ (the temperature where 10 and 50% weight loss occurred), tensile strength, initial modulus, hardness, and adhesive strength of both I-WBPU and B-WBPU systems increased with increasing HMMM content. However, these properties of the I-WBPU system were higher than those of the B-WBPU system at the same HMMM content. These results confirmed the in-situ polymerization used in this study to be a more effective method to improve the properties of the WBPU materials compared to the simple blending process.

• 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.

• Elastomers and Composites
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• v.53 no.4
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• pp.202-206
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• 2018

Five solution styrene butadiene rubber/neodymium butadiene rubber (SSBR/NdBR) composites were manufactured using different ratios of SSBR and NdBR. In this study, the composites were reinforced with NdBR and silica to confirm the physical properties of SSBR used for treads of automobile tires and the dispersibility with silica. The morphologies of the rubber composites were observed using field-emission scanning electron microscopy (FE-SEM). The crosslinking behaviors of the composites were tested using a rubber process analyzer (RPA), and the abrasion resistances were tested using a National Bureau of Standards (NBS) abrasion tester. The hardness values, tensile strengths, and cold resistances of the composites were also tested according to ASTM standards. Increased NdBR content yielded composites with excellent crosslinking properties, abrasion resistances, hardnesses, tensile strengths, and cold resistances. The crosslinking point increased due to the double bond in NdBR, thereby increasing the degree of crosslinking in the composites. The NdBR-reinforced composites exhibited excellent abrasion resistances, which is explained as follows. In SSBR, a breakage is permanent because a resonance structure between styrene and SSBR forms when the molecular backbone is broken during the abrasion process. However, NdBR forms an additional crosslink due to the breakdown of the molecular backbone and high reactivity of the radicals produced. In addition, the low glass transition temperature (Tg) of NdBR provided the rubber composites with excellent cold resistances.

• Polymer(Korea)
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• v.29 no.6
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• pp.599-604
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• 2005

The hyaluronic acid (HA) with excellent biocompatibility has been combined with lactide, the ester dimer of polylactide, with good biodegradability to produce biocompatible materials which can control the period of degradation in a human body. By freeze frying method, HA and lactide were crosslinked with crosslinking agent, 1-ethyl-3-(3-dimethyl aminopropyl) carbodiimide (EDC). Degree of lactide and EDC reaction was determined by the analysis of nuclear magnetic resonance spectroscopy. Both lactyl group and EDC conversion increased as the mole ratio of lactide to HA increased from 5 to 13. The membrane swelled less and became more brittle with the more addition of lactyl group resulting from the higher mole ratio of lactide to HA. Swelling ratio decreased and tensile modulus increased due to the more addition of lactyl group as the EDC concentration increased or reaction temperature decreased. Drug release experiment from various membranes with different degree of crosslinking showed that permeability decreased with increasing degree of crosslinking. The degradation became slower with the more addition of lactyl group. Mechanical property and degradation rate of the synthesized membrane were shown to be controlled through adjusting operation parameters such as mole ratio, temperature, and crosslinking agent concentration.

• Polymer(Korea)
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• v.29 no.4
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• pp.385-391
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• 2005

Reactive melt processing has been carried out to investigate crosslinking characteristics of high density polyethylene OTDPE) with dicummyl peroxide (DCP) and perbutyle peroxide (PBP). The increase of torque in the internal mixer indicated that the crosslinking in HDPE has been occurred by peroxides. As a result, the substantial decrease of density, melting temperature, and melt enthalpy were found while the melt viscosity increased in partially crosslinked HDPE. In the mechanical properties of partially crosslinked HDPE, the increase of maximum strength and the decrease in elongation at break were clearly noticed and these were more pronounced when PBP was applied as a crosslinking agent. It seems that the maximum strength was obtained with reactive processing temperature at $150^{circ}C$, however, the mixing time did not affect to the strength of partially crosslinked HDPE.

• Korean Journal of Food Science and Technology
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• v.28 no.3
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• pp.580-586
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• 1996

Gelatinization behavior and morphology of epichlorohydrin-crosslinked potato starches (XPs) were investigated. Native potato starch showed a very steep single stage swlling pattern, but crosslinked starches showed various patterns with the degree of crosslinking. Swelling power, solubility and light transmittance were reduced drastically as the degree of crosslinking increased. Brabender initial pasting temperature and peak temperature of crosslinked starches increased because the crosslinking reinforces the intermolecular net work of the starches. Although the swelling of the potato starch granule was inhibited by crosslinking as compared to that of the native one, Brabender peak viscosities (6.5% w/v, db) were on the order of 2,500 units for the native potato starch, 3,700 for the XP with 2.300 anhydroglucose units per crosslinking (AGU/CL) and 3,400 for the XP with 2,100 AGU/CL, due to the decreased breakdown of the swollen granule resulting from the resistance to heat and shear. The XP with 1,900 AGU/CL, however, did not show the peak viscosity and the viscosity was on the order of 500 units because of the excessive unhibition of the swelling. Unlike the native potato starch, 6.5%(m/v, db) pastes of the crosslinked potato starches could form gels, which could be predicted from the Brabender setback and consistency index. When the degree of crosslinking is low, random contraction and radial swelling of the granule was possible. As the degree of crosslinking increased, morphological change became similar to the single dimensional tangential swelling observed from the lenticular wheat starch. These morphological change during heating in excess water explained the gelatinization behaviors of crosslinked starches tested.