• Journal of the Korean Chemical Society
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• v.53 no.5
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• pp.547-552
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• 2009

Chitosan, a natural polymer, has been importantly considered as biomedical materials due to its good biocompatibility and various bio-active characteristes. Water soluble chitosan was then copolymerized EGDMA(ethylene glycol dimethacrylate; used as a cross-linking agent for the free-radical copolymerization), MMA (methylmethacrylate), MA (methacrylic acid) in the presence of AIBN (azobisisobutyronitrile) as a radical initiator. The water content and visible transmissibility, ultimate strength of copolymerized ophthalmic polymer were measured to be 24$\sim$59%, 88$\sim$89% and 0.1$\sim$2.4 Kgf, respectively. And also, we tested for antimicrobial activities against staphylococcus aureus, Pseudomonas aeruginosa. They showed that in case of antimicrobial activities, the values including chitosan were much higher than that of the polymers of no including chitosan, suggesting that the copolymer can be used as a novel ophthalmic material of high performance.

• Applied Chemistry for Engineering
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• v.22 no.4
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• pp.411-415
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• 2011

Various types of accelerators, thiuram (TMTD, DPTT), thiazole (MBT, MBTS), and sulfenamide (CBS, NOBS) are added into a silica filled natural rubber compound. Their effects on vulcanization and mechanical properties are investigated. TMTD showed the fastest vulcanization rate, the higer maximum torque ($T_{max}$), and the excellent mechanical properties (300% modulus, tensile strength, elongation). MBT and MBTS showed an intermediate vulcanization rate between thiuram and sulfenamide type and added ones, and also showed the lower $T_{max}$ and mechanical properties compared to that of other compounds. Finally, NOBS showed the slowest vulcanization rate and the lower mechanical property but the moderate $T_{max}$.

• Elastomers and Composites
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• v.31 no.5
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• pp.347-352
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• 1996

A natural rubber was blended with a butadiene rubber with different ratios. A natural rubber, along with three different blends, its ratio varying from 10 to 15 to 20 weight %, were prepared and tested. It was found that inclusion of the butadiene rubber increased cure time, compared to the natural rubber. It is speculated that increased free volume due to the inclusion of butadiene rubber contributed to this effect. Furthermore, inclusion of butadiene rubber led to increase hardness of a sphere, and as a result, the extent of rebound increased sharply.

• Bulletin of the Korean Chemical Society
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• v.35 no.12
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• pp.3658-3660
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• 2014

• Bulletin of the Korean Chemical Society
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• v.35 no.1
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• pp.289-292
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• 2014

• Macromolecular Research
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• v.17 no.10
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• pp.821-824
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• 2009

• Bulletin of the Korean Chemical Society
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• v.31 no.9
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• pp.2668-2671
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• 2010

• Polymer(Korea)
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• v.37 no.3
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• pp.269-275
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• 2013

Thiuram (DPTT, TMTD), thiazole (MBT, MBTS), sulfenamide (CBS, NOBS), and zinc containing thiuram (dithiocarbamate) (ZDBC) type accelerators were added into silica and carbon black filled natural rubber (NR) compounds. Their effects on vulcanization time and rate were compared. The vulcanization rate of thiuram type accelerator added compounds showed the fastest rate, followed by thiazole and sulfenamide types. Silica filled natural rubber (NR) compounds showed a slower vulcanization time ($t_{s2}$, $t_{10}$, $t_{90}$) and lower cure rate index (CRI) than carbon black filled ones upon each accelerator.

• Korean Journal of Crystallography
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• v.12 no.3
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• pp.145-149
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• 2001

The hydrothermal reaction between zinc(II) nitrate Zn₃(PO₄)₂(H₂O) and potassium phosphate dibasic (K₂HPO₄) in the presence of pyrazine gave a three-dimensional zinc-phosphate coordination polymer with an empirical formula of Zn₃(PO₄)₂(H₂O) (1). Compound 1 was characterized by IR spectroscopy, and X-ray diffraction. Crystallographic data for 1: monoclinic space group. P2₁/c, a=8.970(1)Å, b=4.901(1)Å, c=16.759(3)Å, β=94.98(2)°, Z=4, R(wR₂)=0.0332(0.0927).

• Advances in materials Research
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• v.3 no.3
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• pp.175-183
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• 2014

Natural rubber bound phenolic antioxidant, 2,6-di-tert-butyl-4-vinylphenol (2,6-DBVP), was prepared from natural rubber and 2,6-DBVP in both solution and melt state. The 2,6-DBVP had been synthesized from 3,5-di-tert-butyl-4-hydroxybenzaldehyde and methyltriphenylphosphonium iodide ($MePPh_3I$) by Wittig reaction ($0^{\circ}C$ for 2 hrs, $N_2$ atmosphere). The conditions for preparation of natural rubber bound 2,6-DBVP (NR-DBVP) were optimized for both solution state (1 phr BPO and 8 phr 2,6-DBVP at $70^{\circ}C$ for 2 hrs) and for melt state (1 phr BPO and 8 phr 2,6-DBVP at $70^{\circ}C$ for 10 mins, with rotor speed of 60 rpm). A thermoplastic vulcanizate was obtained using a compatibilizer, polypropylene modified with phenolic resin (PhHRJ-PP), in a closed mixer ($180^{\circ}C$ for 3 mins, rotor speed 60 rpm). The antioxidant properties of vulcanized NR-DBVP, using phenolic as the vulcanization system, were similar to NR with the conventional antioxidant BHT. In addition, the antioxidant, water leaching property of the thermoplastic vulcanizate of NR-DBVP/PP were good in comparison to a NR blend with BHT; the morphologies of these thermoplastic vulcanizates were similar.