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Polymer blends based on an epoxy-amine thermoset and a thermoplastic

Effect of thermoplastic on cure reaction and thermal stability of the system

Journal of Thermal Analysis and Calorimetry
Authors: J. López, M. Rico, B. Montero, J. Díez, and Carmen Ramírez

Abstract  

The effect of thermoplastic modification of an epoxy-amine system on the cure reaction, miscibility and thermal stability of the system was investigated. The cure kinetics showed an autocatalytic behavior. Modifier did not affect either the total reaction heat or the achieved maximum conversion but delayed the kinetics. The model of Horie-Kamal corrected by diffusion factor was used to adjust kinetics in the whole range of conversions. The modified systems showed two glass transitions indicating two separated phases, whose compositions were estimated using the Fox and Couchman equations. Modifier did not affect the thermal and thermooxidative stability of the system.

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Journal of Thermal Analysis and Calorimetry
Authors: C. Ramírez, M. Rico, J. M. L. Vilariño, L. Barral, M. Ladra, and B. Montero

Summary Cubic silsesquioxanes offer access to organic/inorganic hybrids. A system formed by a polyhedral oligomeric silsesquioxane (POSS) with eight epoxy reactive groups per molecule, octaepoxycyclohexyldimethylsilyl-POSS, cured with an aliphatic diamine (bisaniline) was studied in different ratios. The characterization of the POSS was carried out by differential scanning calorimetry (DSC) and thermogravimetry (TG). The distribution of species in the reaction of the mixtures POSS/diamine was followed by gel permeation chromatography (GPC). The degradation was studied by thermogravimetric analysis.

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Abstract  

The thermal behaviour of an epoxy resin cured with an amine-POSS was studied using differential scanning calorimetry (DSC) and thermogravimetric (TG) analysis. The kinetic of polymerization reaction and the thermal degradation have been analyzed based on an iso-conversional model. The obtained results showed that the activation energies of both processes depend on the degree of conversion.

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Reaction Kinetics, Mechanisms and Catalysis
Authors: M. R. Granados-Uribe, F. J. Lona-Ramírez, C. Pérez-Pérez, J. Barajas-Fernández, V. Rico Ramírez, and G. González-Alatorre

Abstract

The nitrosation of 1,3-dialkylureas was carried out in the presence of carboxylic acids and halides in an aqueous perchloric medium. The aim of this work was to validate the proposed mechanism for the nitrosation of such substrates. In accordance with the rate limiting step of the proposed mechanism, the protonic transfer to the solvent, basic catalysis and an absence of catalysis by halides should be observed. The Br⊘nsted parameters were determined by basic general catalysis.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: I. Gonçalves, A. Ramalho, J. Salgado, J. Pertusa, A. Irles, F. Mascarenhas, M. Castro, F. Valle, J. Rico, and V. Alcober

Abstract  

The goal of this work is to pursue the research activity in BNC and the installation of a therapy facility in the position presently occupied by the thermal column. With these objectives the experimental studies in mice and cells are continuing while improvements in the facilities are created or prepared. For this effect: (1) the installation of lead shield in the vertical access of the thermal column, which resulted in an enhancement of the Φth toD γ ratio, was performed, (2) the adaptation of a beam tube to deliver a dominantly thermal or epithermal beam in two possible beam openings is being done and (3) Monte Carlo calculations aiming at the optimization of the conditions for the therapy installation are in progress.

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