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RISS 인기검색어
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- 저자 : Salami-Kalajahi Mehdi (검색결과 4 건)
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EFFECT OF CARBON NANOTUBES ON THE KINETICS OF IN SITU POLYMERIZATION OF METHYL METHACRYLATE
MEHDI SALAMI-KALAJAHI,VAHID HADDADI-ASL,FARID BEHBOODI-SADABAD,SAEID RAHIMI-RAZIN,HOSSEIN ROGHANI-MAMAQANI,MAHMOUD HEMMATI 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2012 NANO Vol.7 No.1
The effect of carbon nanotubes on the kinetics of free radical polymerization of methyl methacrylate (MMA) was investigated. To do this, pristine, acid treated, alcoholic and methacrylate-modified carbon nanotubes with different loadings were used and Conversion, molecular weight and polydispersity index (PDI) of all samples were monitored during polymerization. The results show that carbon nanotubes induce an induction time to polymerization system which is independent of modification system while decrease in monomer conversion can be improved by developing organic moieties on surface. Molecular weight and polydispersity index for free and attached-on-surface chains were studied separately and different kinetics behaviors were observed for them. Molecular weight of free chains was increased by adding carbon nanotubes while more modified nanotubes resulted in much increased molecular weight. On the other hand, more system stability of more modified nanotubes, which was tested using UV-Visible spectra, resulted in higher molecular weights. Adding more nanotubes in the case of MMA-modified nanotubes caused to determine an optimum loading value to reach maximum molecular weight of free chains which was ascribed to system stability according to UV-Visible results. In this optimum loading value, free chains had minimum PDI value. However, increasing carbon nanotubes content led to decreased molecular weight of attached chains while PDI values increased because of shielding effect as physical phenomenon.
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ABBAS ASFADEH,VAHID HADDADI-ASL,MEHDI SALAMI-KALAJAHI,MOHAMMADREZA SARSABILI,HOSSEIN ROGHANI-MAMAQANI 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2013 NANO Vol.8 No.2
Effect of pristine and modified MCM-41 on the kinetics of styrene atom transfer radical polymerization (ATRP) was studied using a double bound containing modifier at 110°C. Conversion, molecular weight and PDI were obtained during the polymerization reactions to study the polymerization kinetics. Addition of the both types of MCM-41 has resulted in inconsiderable variations on the kinetics of polymerization. A similar trend is observed for the molecular weight of the free chains; however, increasing MCM-41 content results in higher PDI values. Also, surface modification of MCM-41 results in lower polymerization rates. In the case of grafted chains, molecular weight and PDI values increase by increasing MCM-41 content.
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Ebrahimi Hamidreza,Roghani-Mamaqani Hossein,Salami-Kalajahi Mehdi,Shahi Sina,Abdollahi Amin 한국탄소학회 2020 Carbon Letters Vol.30 No.1
Chemical incorporation of epoxy-modifed graphitic layers in epoxy/novolac phenolic resin matrices was carried out through co-curing of epoxy and novolac resins using triphenylphosphine as catalyst. First, (3-glycidyloxypropyl) trimethoxysilane (GPTMS) was grafted on graphene oxide (GO) surface to obtain epoxidized GO layers. Then epoxy resin and GPTMS-mod�ifed GO were incorporated into thermosetting reaction using novolac resin in the presence of triphenylphosphine. Covalent attachment of GPTMS-modifed GO to the resin matrices resulted in a hybrid composite with high thermal characteristics. Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis (TGA), X-ray dif�fraction, and Raman spectroscopy were used for approving modifcation of GO with GPTMS. The images resulted from scanning and transmission electron microscopies exhibited GO layers with lots of creases turning to smooth layers with a few thin ripples after modifcation with GPTMS. TGA results showed that thermal characteristics of resins were improved by the addition of GPTMS-modifed GO. Char residue of the hybrid composites containing 0.5 and 1 wt% of GPTMS-modifed GO reached 28.1 and 34.3%, respectively. Also, their maximum thermal degradation temperature was also increased by the incorporation of GPTMS-modifed GO.
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Izadi Mohammadreza,Mardani Hanieh,Roghani-Mamaqani Hossein,Salami-Kalajahi Mehdi 한국탄소학회 2021 Carbon Letters Vol.31 No.4
Carbon nanotube (CNT) grafted with hyperbranched poly(amidoamine) (PAMAM) dendrimer (CNTD) were used as a multifunctional curing and composite agent of polyurethane (PU) terminated with epoxy units. Amino-functionalized CNT was used as the core for grafting the frst generation of PAMAM dendrimer by sequential addition of methyl acrylate and ethylenediamine. Two diferent epoxy-terminated PUs (PUB and PU-PMDA) were prepared from the reaction of poly(ethylene glycol), excess amounts of hexamethylene diisocyanate, and diferent chain extenders (1,4-butanediol for PUB and pyromellitic dianhydride (PMDA) for PU-PMDA), and subsequent end group transformation of the isocyanate groups to epoxy functionalities using glycidol. Fourier transform infrared spectra and thermogravimetric analysis (TGA) results showed that CNTD was successfully prepared. TGA thermograms revealed that thermal decomposition of composites were carried out in two main steps related to the soft and hard segments. In addition, char content and thermal stability of the composites were increased with increasing the CNTD content. Most importantly, the PMDA chain extender resulted in high thermal stability of the epoxy-terminated PU composites. X-ray difraction and scanning and transmission electron microscopies presented morphological and structural properties of nanotubes and hybrid composites.
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