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로상철,김창근,관혁중 한국고분자학회 2012 Macromolecular Research Vol.20 No.5
Nanocomposites of novolac-type phenolic resins having various molecular weights with a series of organoclays containing organic amine salts were prepared by melt processing. The effects of the molecular weight of novolac resin and the amine structure of organoclay on composite morphology and physical properties were examined. Composites containing organoclay exhibited the intercalated state with shifts in gallery spacing regardless of the molecular weight of novolac resin. The extent of silicate platelet intercalation increased as molecular weight of novolac resin increased and the number of long alkyl tails decreased from two to one. Novolac resin/organoclay composites cured with hexamethylenetetramine (HMTA) always exhibited better flexural and Izod impact strengths than the novolac resin cured with HMTA when the molecular weight of novolac resin was fixed. Among the nanocomposites prepared here using organoclays, those with higher platelet intercalation generally showed better flexural and Izod impact strengths. However, resin-coated sands prepared from organoclay containing one long alkyl tail exhibited only better flexural strength than that prepared from novolac resin.
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로상철,김창근,홍지혜 한국고분자학회 2012 Macromolecular Research Vol.20 No.2
To develop highly efficient proton exchange membranes (PEMs), a series of partially sulfonated and crosslinked copolymers, i.e., poly(ethylene glycol dimethylmethacrylate-co-styrene sulfonic acid) (P(EGDMA-SSA))and poly(diethylene glycol dimethylmethacrylate-co-styrene sulfonic acid) (P(DEGDMA-SSA)), were synthesized using radical copolymerization. The compositions of the copolymers were quantified using proton nuclear magnetic resonance. The proton conductivities, methanol and water uptakes, and methanol permeabilities of the PEMs prepared from these copolymers increased as SSA content increased. The proton conductivities and uptakes of both copolymers increased abruptly when the copolymers contained >15 mol% SSA. When the P(EGDMA-SSA) and P(DEGDMA-SSA) copolymers contained the same mol% SSA, the methanol permeabilities and uptakes of the former were lower than those of the latter, while the former exhibited better proton conductivity. The PEM prepared from P(EGDMA-SSA) copolymer containing >30 mol% SSA exhibited better proton conductivity and lower methanol permeability than Nafion 117. Furthermore, these membranes exhibited considerably thermal, hydrolytic, and oxidative stabilities. Consequently, PEMs, especially those desirable for use in direct methanol fuel cells, could be fabricated from P(EGDMA-SSA) copolymers and are appealing alternatives for Nafion membranes under mild conditions.
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임현구,로상철,김창근 한국고분자학회 2013 Macromolecular Research Vol.21 No.6
Thermoplastic polyurethane elastomer (TPU) is used as an encapsulant in undersea sonar devices. In order to fabricate desirable composites for underwater applications, TPU prepared from poly(tetramethylene glycol)(PTMG), and methyl diphenyl diisocyanate (MDI) was blended with a multiwalled carbon nanotube (MWCNT). TPU grafted MWCNT (TPU-g-MWCNT) were prepared to fabricate a composite that has better mechanical strength and interfacial adhesion between the TPU matrix and the MWCNTs. The tensile strength of the composite increased with increasing MWCNT content. At a fixed MWCNT content in the composite, the TPU/TPU-g-MWCNT composite exhibited superior tensile strength compared to the TPU composite with pristine MWCNT. The swelling ratio of TPU composite with pristine MWCNT was higher than that of TPU. However, the swelling ratio of the TPU/TPU-g-MWCNT composite was lower than the latter when the composite contains more than 0.5 wt% of TPU-g-MWCNT. In addition, the TPU/TPU-g-MWCNT composite exhibited enhanced mechanical strength and a reduced swelling ratio as compared to TPU after being impregnated with seawater or paraffin oil.
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