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Journal of Thermal Analysis and Calorimetry
Authors: L. Barral, J. Cano, J. López, I. López-Bueno, P. Nogueira, C. Ramírez, A. Torres, and M. Abad

Abstract  

Cure kinetics using a differential scanning calorimetry (DSC) technique were analyzed for a thermoplastic modified tetraglycidyl-4,4′-diaminodiphenylmethane (TGDDM) epoxy resin cured with diaminodiphenylsulphone (DDS), an aromatic diamine. The neat resin and its blends with the poly(styrene-co-acrylonitrile) (SAN) of various compositions were studied by applying a phenomenological model proposed by Kamal. Kinetic parameters were determined by fitting experimental data. This model gives a good description of cure kinetics up to the onset of vitrification. Diffusion control was incorporated to describe the cure in the latter stages of cure. The results showed that the addition of SAN did not alter the nature of the reaction, but the reaction rates and final conversions decreased when SAN contents increase, due to reduction of mobility of the reacting species.

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Journal of Thermal Analysis and Calorimetry
Authors: L. Barral, J. Cano, J. López, I. López-Bueno, P. Nogueira, C. Ramírez, A. Torres, and M. Abad

Abstract  

The effect of thermal degradation on the mechanical behaviour of a system containing both tetraglycidyl-4-4′-diaminodiphenylmethane (TGDDM) and a multifunctional novolac glycidyl ether (EPN) resins, cured with 4,4′-diaminodiphenylsulphone (DDS) has been studied using dynamic mechanical analysis (DMA) and tensile tests. Different curing paths using the isothermal time-temperature-transformation (TTT) diagram for this system were designed, obtaining thermosetting materials with different conversions. The influences of the degree of cure and of the aging temperature were also studied. The results showed different trends in the dynamic mechanical properties and an increase in the stiffness of the material with increasing aging time. Changes were faster and more intense with the higher temperature.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: J. D. T. Arruda-Neto, A. C. Cestari, C. B. Zamboni, M. Saiki, G. P. Nogueira, L. E. C. Fonseca, M. V. Manso-Guevara, A. Deppman, V. P. Likhachev, J. Mesa, O. A. M. Helene, S. A. C. Jorge, M. N. Martins, A. N. Gouveia, O. Rodriguez, F. Guzmán, and F. Garcia

Summary  

Neutron activation analysis has been used to study uranium incorporation in poultry bones as function of chow doped with: (a) uranium (20 ppm); (b) U-doped food (20 ppm) plus phytase (120 ppm) and (c) U-doped food (20 ppm) plus phytase (180 ppm). To investigate this situation experiments involving several groups of Cobb broilers was performed. Two animals per group were sacrificed weekly up to their adultness and uranium concentration in the tibia was measured. It was observed that the concentration of uranium (µg U/g bone) is decreasing all along the animal life spanning period of 14-42 days. This behavior suggests that the skeleton mass is growing faster than the corresponding accumulation of uranium. The administration of phytase seems not to alter this scenario.

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