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2. Millable polyurethane/organoclay nanocomposites: preparation, characterization, and properties

Author

Siliani, M., López Manchado, M. A., Valentin, J. L., Arroyo Ramos, Victor Miguel, Marcos, A., Khayet Souhaimi, Mohamed, García Villaluenga, Juan Pedro, Siliani, M., López Manchado, M. A., Valentin, J. L., Arroyo Ramos, Victor Miguel, Marcos, A., Khayet Souhaimi, Mohamed, and García Villaluenga, Juan Pedro

Abstract

© 2007 American Scientific Publishers. The authors wish to thank the CICYT, MAT 2004-00825 and the Spanish Ministry of Science and Technology (MCYT), PPQ2003-03299, for financial support and Dr. López Manchado for the concession of a Ramón y Cajal contract (MCYT)., Novel millable polyurethane (PU)/organoclay nanocomposites have been successfully prepared by conventional transformation techniques. One natural (C6A) and two organically modified (C15A and C30B) montmorillonites have been used as clays for preparing PU nanocomposites. The optimum dispersion of nanofiller at a nanometer scale in PU matrix was confirmed by X-ray diffraction patterns and transmission electron microscopy. A substantial improvement of the PU properties by addition of only a small amount of organoclay was observed. It is worthy to note that the organoclays show a different interfacial interaction with the PU matrix, which was reflected in different macroscopic properties. Thus, C30B organoclay seems to react with PU chains to form covalent bonds, while C15A only interacts physically with PU chains. Mechanical and barrier properties are analyzed., CICYT, Spanish Ministry of Science and Technology (MCYT), Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

Published
2023

3. Gas transport properties of polypropylene/clay composite membranes

Author

García Villaluenga, Juan Pedro, Khayet Souhaimi, Mohamed, Lopez Manchado, M. A., Valentin, J. L., Seoane Rodríguez, Benjamín, Mengual Cabezón, Juan Ignacio, García Villaluenga, Juan Pedro, Khayet Souhaimi, Mohamed, Lopez Manchado, M. A., Valentin, J. L., Seoane Rodríguez, Benjamín, and Mengual Cabezón, Juan Ignacio

Abstract

© 2007 Elsevier Ltd. The authors of this study gratefully acknowledge the financial support of the Ministry of Science and Technology (MCYT, Spain) through its project No. PPQ2003-03299 and MAT 2004-00825. Dr. López Manchado also acknowledges the concession of a Ramón & Cajal contract from the MCYT., Polypropylene membranes modified with natural and organically modified montmorillonite clays were prepared. The permeability, diffusivity and solubility of helium, oxygen and nitrogen were determined for the unfilled and filled membranes over the temperature range 25-65 degrees C. Physical properties of polypropylene membranes were investigated using X-ray diffraction, thermogravimetric analyser, tensile testing and differential scanning calorimetry. The results showed that the filled membranes exhibit lower gas permeability compared to the unfilled polypropylene membrane. For helium, a reduced diffusivity is mainly responsible for the reduction in the permeability, in contrast, for nitrogen and oxygen, both diffusivity and solubility were reduced by the presence of fillers. The X-ray diffraction spectra showed that the incorporation of the unmodified and modified clay did not affect the crystallographic nature of polypropylene., Ministry of Science and Technology (MCYT, Spain), Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

Published
2023

4. The Cabo Frio Upwelling System, Brazil

Author

Valentin, J. L., Caldwell, M. M., editor, Heldmaier, G., editor, Lange, O. L., editor, Mooney, H. A., editor, Schulze, E.-D., editor, Sommer, U., editor, Seeliger, Ulrich, editor, and Kjerfve, Björn, editor

Published
2001
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11. NEW INSIGHTS IN THE CNT-RUBBER STRUCTURE FOR A RATIONAL DEVELOPMENT OF ADVANCED MATERIALS

Author

Valentin, J. L., Bernal-Ortega, Pilar, Bernal, M. Mar, González-Jiménez, A., Rodrigo Navarro Crespo, Ministerio de Economía y Competitividad (España), and Ministerio de Ciencia, Innovación y Universidades (España)

Subjects
Composite structures, Viscoelastic properties, Rubber reinforcement, 1H DQ-NMR
Abstract

In this work, a systematic characterization of CNT rubber structure has been performed by using a combination of exper i- mental techniques (including advanced 1 H time domain NMR methods) and the last developed analysis procedures (including stress an d strain amplification factors) in order to improve the understanding about the mechanical and viscoelastic properties of these nano composites. According the obtained results, these promising materials could have some li m itations to be applied in high per formance tire tread compounds (mainly related to the rolling resistance and fuel consumption) because of the difficulty of dispersion of CNT in ru b- ber matrices (high filler networking), the strong influence of CNT in the vulcanization process (low cross li nk density and high network defects) and the nature of filler rubber interactions (high energy dissipation associated to the rupture of filler rubber interactions at high strain amplitudes). To overcome th ese issue s , the CNT have been surface modified with oxygen bearing groups and sulfur., The authors thank the financial support provided by the Ministerio de Ciencia e Innovación (MCINN) through the Project MAT2014 52644 R, MAT2017 87204 and an FPI grant.

Published
2019

15. Vernetzungseffizienz von Naturkautschuk: Effekt der HeterogenitaÈten auf die physikalischen Eigenschaften

Author

González, L., Rodríguez, A., Valentin, J. L., Marcos-Fernández, A., Pilar Posadas, and Comisión Interministerial de Ciencia y Tecnología, CICYT (España)

Subjects
Crosslinking, Vulcanisation, Physical properties, Physikalische eigenschaften, Vernetzung, Naturkautschuk, Natural rubber
Abstract

6 páginas, 9 figuras, 2 esquemas, 4 tablas., [EN] The scope of this article is to study the sulphur vulcanisation of natural rubber in the presence as accelerator of N cyclohexyl 2 benzothiazyl sulfenamide (CBS). Two series of compounds were prepared with conventional and efficient cured systems. Experimental results indicates that abstraction of allylic hydrogen and addition to the double bonds can act as a mechanism for crosslinking. The addition reaction may give rise to a polymerisation reaction between adjacent double bonds that generating a heterogeneous network with effects a on the physical properties of the vulcanizates., [AL] Ziel der vorliegenden Arbeit ist es die Schwefelvernetzung in Gegenwart von CBS zu untersuchen. Zwei Gruppen von Compounds wurden jeweils mit einem "conventional" und einem "efficient" Vernetzungssystem vulkanisiert. Die experimentellen Ergebnisse zeigen, dass die Abstraktion von Allylprotonen und die Addition an Doppelbindungen als Mechanismen der Vernetzung in Frage kommen. Die Additionsreaktion kann eine Polymerisation benachbarter Doppelbindung auslösen, so dass ein heterogenes Netzwerk entsteht welches die physikalischen Eigenschaften beeinflusst., The authors wish to thank the Spanish Interministerial Commission for Science & Technology (CICYT) for partial support, project MAT 2005-00825.

Published
2005

16. Embryonic development time of Penilia avirostris Dana, 1852 in a tropical bay in Brazil

Author

Valentin, J. L. and Marazzo, A.

Subjects
zooplankton, desenvolvimento embrionário, Penilia avirostris, embryonic development, Brasil, baía de Guanabara, zooplâncton, Cladocera, Guanabara Bay, Brazil
Abstract

Development time of embryos in the brood pouch of the cladoceran Penilia avirostris Dana, 1852, was estimated by collecting zooplankton daily for 15 days in surface water of Guanabara Bay, Brazil. Each day the maturity stage of embryos of 90 parthenogenic females was noted. Total development time (egg to birth) varied from 2 to 3 days, the immature phase (stages I to IV) being generally longer (2 days) than intermediate and mature phases (1 day, stages V to XII). Similar results were obtained from Bottrell's equation, which takes water temperature into account. O tempo de desenvolvimento na câmara incubadora dos embriões do cladócero Penilia avirostris Dana, 1852, foi estimado a partir do zooplâncton coletado na água superficial da Baía de Guanabara, Brasil, diariamente, durante 15 dias. A cada dia, foi anotado o estágio de maturidade dos embriões de 90 fêmeas partenogenéticas. O tempo de desenvolvimento total (do ovo até o nascimento) variou de 2 a 3 dias, sendo a fase imatura (estágios I e IV) geralmente mais longa (2 dias) que as fases intermediárias e maturas (1 dia, estágios V a XII). Resultados similares foram obtidos com a equação de Bottrell, que leva em conta a temperatura da água.

Published
2004

18. Millable polyurethane/organoclay nanocomposites: preparation, characterization, and properties

Author

Siliani, M., López Manchado, M. A., Valentin, J. L., Arroyo Ramos, Victor Miguel, Marcos, A., Khayet Souhaimi, Mohamed, García Villaluenga, Juan Pedro, Siliani, M., López Manchado, M. A., Valentin, J. L., Arroyo Ramos, Victor Miguel, Marcos, A., Khayet Souhaimi, Mohamed, and García Villaluenga, Juan Pedro

Abstract

© 2007 American Scientific Publishers. The authors wish to thank the CICYT, MAT 2004-00825 and the Spanish Ministry of Science and Technology (MCYT), PPQ2003-03299, for financial support and Dr. López Manchado for the concession of a Ramón y Cajal contract (MCYT)., Novel millable polyurethane (PU)/organoclay nanocomposites have been successfully prepared by conventional transformation techniques. One natural (C6A) and two organically modified (C15A and C30B) montmorillonites have been used as clays for preparing PU nanocomposites. The optimum dispersion of nanofiller at a nanometer scale in PU matrix was confirmed by X-ray diffraction patterns and transmission electron microscopy. A substantial improvement of the PU properties by addition of only a small amount of organoclay was observed. It is worthy to note that the organoclays show a different interfacial interaction with the PU matrix, which was reflected in different macroscopic properties. Thus, C30B organoclay seems to react with PU chains to form covalent bonds, while C15A only interacts physically with PU chains. Mechanical and barrier properties are analyzed., CICYT, Spanish Ministry of Science and Technology (MCYT), Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

Published
2007

19. Gas transport properties of polypropylene/clay composite membranes

Author

García Villaluenga, Juan Pedro, Khayet Souhaimi, Mohamed, Lopez Manchado, M. A., Valentin, J. L., Seoane Rodríguez, Benjamín, Mengual Cabezón, Juan Ignacio, García Villaluenga, Juan Pedro, Khayet Souhaimi, Mohamed, Lopez Manchado, M. A., Valentin, J. L., Seoane Rodríguez, Benjamín, and Mengual Cabezón, Juan Ignacio

Abstract

© 2007 Elsevier Ltd. The authors of this study gratefully acknowledge the financial support of the Ministry of Science and Technology (MCYT, Spain) through its project No. PPQ2003-03299 and MAT 2004-00825. Dr. López Manchado also acknowledges the concession of a Ramón & Cajal contract from the MCYT., Polypropylene membranes modified with natural and organically modified montmorillonite clays were prepared. The permeability, diffusivity and solubility of helium, oxygen and nitrogen were determined for the unfilled and filled membranes over the temperature range 25-65 degrees C. Physical properties of polypropylene membranes were investigated using X-ray diffraction, thermogravimetric analyser, tensile testing and differential scanning calorimetry. The results showed that the filled membranes exhibit lower gas permeability compared to the unfilled polypropylene membrane. For helium, a reduced diffusivity is mainly responsible for the reduction in the permeability, in contrast, for nitrogen and oxygen, both diffusivity and solubility were reduced by the presence of fillers. The X-ray diffraction spectra showed that the incorporation of the unmodified and modified clay did not affect the crystallographic nature of polypropylene., Ministry of Science and Technology (MCYT, Spain), Depto. de Estructura de la Materia, Física Térmica y Electrónica, Fac. de Ciencias Físicas, TRUE, pub

Published
2007

23. Hatching rates of resting eggs of 'Cladocera' (Crustacea; Branchiopoda) at a tropical bay, Brazil.

Author

Mugrabe, G., Barros, S., Marazzo, A., and Valentin, J. L.

Subjects
CLADOCERA, EGG incubation, BRANCHIOPODA, CRUSTACEA, ENTOMOSTRACA
Abstract

Copyright of Brazilian Journal of Biology is the property of Instituto Internacional de Ecologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Published
2007
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