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| Registros recuperados : 488 | |
| 143. |  | ALVAREZ, R.; SANTANATOGLIA, O. J.; DANIEL, P. E.; GARCIA, R. Respiration and specific activity of soil microbial biomass under conventional and recuced tillage. Pesquisa Agropecuária Brasileira, Brasília, DF, v. 30, n. 5, p. 701-709, maio 1995. Título em português: Repiração e atividade específica da biomassa microbiana de um solo sob lavra convencional e reduzida.| Biblioteca(s): Embrapa Unidades Centrais. |
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| 144. | | PASSOS, C. A. M.; COUTO, L.; GARCIA, R. Viabilidade financeira do uso método Taungya com Eucalyptus urophylla na Região de Divinópolis, MG. In: INTERNATIONAL CONGRESS AND EXHIBITION ON FOREST, 5., 1999, Curitiba. Forest 99: [resumos]. Rio de Janeiro: BIOSFERA, 1999. 1 CD-ROM. Autoria bilíngue: CONGRESSO E EXPOSICAO INTERNACIONAL SOBRE FLORESTAS, 5., 1999, Curitiba.| Biblioteca(s): Embrapa Florestas. |
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| 149. | | ANDRADE, C. M. S. de; GARCIA, R.; VALENTIM, J. F.; FERREIRA, O. G. Productivity, utilization efficiency and sward targets for mixed pastures of marandugrass, forage peanut and tropical kudzu. Revista Brasileira de Zootecnia, Viçosa, v. 41, n. 3, p. 512-520, 2012.| Biblioteca(s): Embrapa Acre. |
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| 151. | | ROSOLEM, C. A.; CALONEGO, J. C.; FOLONI, J. S. S.; GARCIA, R. A. Potássio lixiviado da palha de aveia-preta e milheto após a dessecação química Pesquisa Agropecuária Brasileira, Brasília, DF, v. 42, n. 8, p. 1169-1175, ago. 2007 Título em inglês: Potassium leaching from black oat and pearl millet straw after chemical desiccation.| Biblioteca(s): Embrapa Unidades Centrais. |
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| 152. | | MOTTA, I. de S.; COMUNELLO, E.; GARCIA, R. A.; AMORIN, A. dos S.; DRUZIANI, C. C. Plantio direto de hortaliças: pré-cultivo do milho-verde solteiro e consorciado com plantas de cobertura para produção de palhada. In: ENCONTRO NACIONAL DE PLANTIO DIRETO NA PALHA, 18., ENCONTRO MUNDIAL DO SISTEMA PLANTIO DIRETO, 1., 2022, Foz do Iguaçu. Sistema plantio direto: preservando o solo, a vida e as gerações futuras: anais. Londrina: FEBRAPDP, 2022. p. 211. Editores: Rafael Silvaro; Marie Luise Carolina Bartz.| Biblioteca(s): Embrapa Agropecuária Oeste. |
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| Registros recuperados : 488 | |
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Registro Completo
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Biblioteca(s): |
Embrapa Instrumentação. |
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Data corrente: |
30/03/2022 |
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Data da última atualização: |
23/01/2024 |
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Tipo da produção científica: |
Artigo em Periódico Indexado |
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Circulação/Nível: |
B - 1 |
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Autoria: |
GARCIA, R. H. S.; FILGUEIRAS, J. G.; COLNAGO, L. A.; AZEVEDO, E. R. |
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Afiliação: |
LUIZ ALBERTO COLNAGO, CNPDIA. |
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Título: |
Real-Time monitoring polymerization reactions using dipolar echoes in 1H time domain NMR at a low magnetic field. |
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Ano de publicação: |
2022 |
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Fonte/Imprenta: |
Molecules, v. 27, 566, 2022. |
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Páginas: |
14 p. |
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DOI: |
https://doi.org/10.3390/molecules27020566 |
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Idioma: |
Inglês |
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Conteúdo: |
1H time domain nuclear magnetic resonance (1H TD-NMR) at a low magnetic field becomes a powerful technique for the structure and dynamics characterization of soft organic materials. This relies mostly on the method sensitivity to the 1H-1H magnetic dipolar couplings, which depend on the molecular orientation with respect to the applied magnetic field. On the other hand, the good sensitivity of the 1H detection makes it possible to monitor real time processes that modify the dipolar coupling as a result of changes in the molecular mobility. In this regard, the so-called dipolar echoes technique can increase the sensitivity and accuracy of the real-time monitoring. In this article we evaluate the performance of commonly used 1H TD-NMR dipolar echo methods for probing polymerization reactions. As a proof of principle, we monitor the cure of a commercial epoxy resin,using techniques such as mixed-Magic Sandwich Echo (MSE), Rhim Kessemeier—Radiofrequency Optimized Solid Echo (RK-ROSE) and Dipolar Filtered Magic Sandwich Echo (DF-MSE). Applying a reaction kinetic model that supposes simultaneous autocatalytic and noncatalytic reaction pathways,we show the analysis to obtain the rate and activation energy for the epoxy curing reaction using the NMR data. The results obtained using the different NMR methods are in good agreement among them and also results reported in the literature for similar samples. This demonstrates that any of these dipolar echo pulse sequences can be efficiently used for monitoring and characterizing this type of reaction. Nonetheless, the DF-MSE method showed intrinsic advantages, such as easier data handling and processing, and seems to be the method of choice for monitoring this type of reaction.In general, the procedure is suitable for characterizing reactions involving the formation of solidproducts from liquid reagents, with some adaptations concerning the reaction model. Menos1H time domain nuclear magnetic resonance (1H TD-NMR) at a low magnetic field becomes a powerful technique for the structure and dynamics characterization of soft organic materials. This relies mostly on the method sensitivity to the 1H-1H magnetic dipolar couplings, which depend on the molecular orientation with respect to the applied magnetic field. On the other hand, the good sensitivity of the 1H detection makes it possible to monitor real time processes that modify the dipolar coupling as a result of changes in the molecular mobility. In this regard, the so-called dipolar echoes technique can increase the sensitivity and accuracy of the real-time monitoring. In this article we evaluate the performance of commonly used 1H TD-NMR dipolar echo methods for probing polymerization reactions. As a proof of principle, we monitor the cure of a commercial epoxy resin,using techniques such as mixed-Magic Sandwich Echo (MSE), Rhim Kessemeier—Radiofrequency Optimized Solid Echo (RK-ROSE) and Dipolar Filtered Magic Sandwich Echo (DF-MSE). Applying a reaction kinetic model that supposes simultaneous autocatalytic and noncatalytic reaction pathways,we show the analysis to obtain the rate and activation energy for the epoxy curing reaction using the NMR data. The results obtained using the different NMR methods are in good agreement among them and also results reported in the literature for similar samples. This demonstrates that any of these dipolar echo pulse sequences can be efficien... Mostrar Tudo |
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Palavras-Chave: |
Autocatalytic reaction; Dipolar echoes; Epoxy resin; Ime-domain NMR; Polymerization reaction. |
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Categoria do assunto: |
-- |
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URL: |
https://ainfo.cnptia.embrapa.br/digital/bitstream/item/233135/1/P-Real-Time-Monitoring-Polymerization-Reactions-Using-Dipolar.pdf
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Marc: |
LEADER 02669naa a2200241 a 4500
001 2141628
005 2024-01-23
008 2022 bl uuuu u00u1 u #d
024 7 $ahttps://doi.org/10.3390/molecules27020566$2DOI
100 1 $aGARCIA, R. H. S.
245 $aReal-Time monitoring polymerization reactions using dipolar echoes in 1H time domain NMR at a low magnetic field.$h[electronic resource]
260 $c2022
300 $a14 p.
520 $a1H time domain nuclear magnetic resonance (1H TD-NMR) at a low magnetic field becomes a powerful technique for the structure and dynamics characterization of soft organic materials. This relies mostly on the method sensitivity to the 1H-1H magnetic dipolar couplings, which depend on the molecular orientation with respect to the applied magnetic field. On the other hand, the good sensitivity of the 1H detection makes it possible to monitor real time processes that modify the dipolar coupling as a result of changes in the molecular mobility. In this regard, the so-called dipolar echoes technique can increase the sensitivity and accuracy of the real-time monitoring. In this article we evaluate the performance of commonly used 1H TD-NMR dipolar echo methods for probing polymerization reactions. As a proof of principle, we monitor the cure of a commercial epoxy resin,using techniques such as mixed-Magic Sandwich Echo (MSE), Rhim Kessemeier—Radiofrequency Optimized Solid Echo (RK-ROSE) and Dipolar Filtered Magic Sandwich Echo (DF-MSE). Applying a reaction kinetic model that supposes simultaneous autocatalytic and noncatalytic reaction pathways,we show the analysis to obtain the rate and activation energy for the epoxy curing reaction using the NMR data. The results obtained using the different NMR methods are in good agreement among them and also results reported in the literature for similar samples. This demonstrates that any of these dipolar echo pulse sequences can be efficiently used for monitoring and characterizing this type of reaction. Nonetheless, the DF-MSE method showed intrinsic advantages, such as easier data handling and processing, and seems to be the method of choice for monitoring this type of reaction.In general, the procedure is suitable for characterizing reactions involving the formation of solidproducts from liquid reagents, with some adaptations concerning the reaction model.
653 $aAutocatalytic reaction
653 $aDipolar echoes
653 $aEpoxy resin
653 $aIme-domain NMR
653 $aPolymerization reaction
700 1 $aFILGUEIRAS, J. G.
700 1 $aCOLNAGO, L. A.
700 1 $aAZEVEDO, E. R.
773 $tMolecules$gv. 27, 566, 2022.
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