Authors:Lisardo Núñez, F. Fraga López, L. Fraga Grueiro, and J. A. Rodriguez Añón
From the peak reaction temperatures as a function of heating rate, the activation energies were obtained for a system consisting of an epoxy resin (Badgen=0) and a curing agent (isophorone diamine), using a Perkin Elmer DSC7 operated in the dynamic mode. At the same time, the Arrhenius law was used to calculate rate constants.
Authors:L. Núñez-Regueira, M. Villanueva, and I. Fraga-Rivas
study of the degradation of a polymer is important because it can determine
the upper temperature limit, the mechanism of a solid-state process, and the
life-time for this system. Since the behavior of thermosets is affected by
the selection of the curing cycle, it is important to investigate the changes
which take place during the thermal degradation of these materials when a
change on the sequence of time and temperature is introduced during the curing
this work, the thermal degradation of two epoxy systems diglycidyl ether of
bisphenol A (BADGE n=0)/1, 2 diamine cyclohexane
(DCH) cured through different sequences of time and temperature was studied
by thermogravimetric analysis in order to determine the reaction mechanism
of the degradation processes, and also to check the influence of the curing
cycle on this mechanism. Values obtained using different kinetic methods were
compared to the value obtained by Kissinger’s method (differential method
which do not require a knowledge of the n-order
reaction mechanism), and to that obtained through Flynn–Wall–Ozawa
method in a previous work.
Authors:Lisardo Núñez, M. Villaneuva, B Rial, M. Núñez, and L. Fraga
The thermal degradation of the epoxy system diglycidyl ether of bisphenol A (BADGE n=0)/1,2-diamine cyclohexane (DCH) containing different concentrations of an epoxy reactive diluent was studied by thermogravimetric
analysis in order to determine the reaction mechanism of the degradation process and to compare it with the results for the
same system without diluent. The value of the activation energy, necessary for this study, was calculated using various integral
and differential methods. Values obtained using the different methods were compared to the value obtained by the Flynn-Wall-Ozawa"s
method (between 193-240 kJ mol-1 depending on the diluent concentration) with does not require a knowledge of the nth order reaction mechanism. All the experimental
results were compared to master curves in the range of Doyle"s approximation (20-35% of conversion). Analysis of the results
suggests that the reaction mechanism could be F2, F3, or A2 type.
Authors:J. Añón, M. Añón, F. Fraga, J. Palacios, and L. Regueira
Following a method based on the procedure given by Hubbardet al.  the calorific values of combustion in oxygen at 298.15 K were measured by static-bomb calorimetry for forest residues.
This waste mainly coming from mount reforestation, construction of firebreaks, etc., constitutes an important risk to originate
forest fire. From combustion experiments the mean calorific value of all species studied was found close to 19 000 kJ·kg−1, similar to calorific values of Municipal Waste. It can be concluded that this forest residues can be used as an additional
fuel to be added to Municipal Solid Waste in energy recovery plants. By doing this, energy, in this moment lost as abandoned
residues, can be recovered. At the same time the elimination of this waste minimizes the risk of forest fires. Our results
reasonably agree with literature values.
Authors:F. Fraga, T. Salgado, J. Rodríguez Añon, and L. Nuñez Regueira
Mechanical behaviour play an important role in the election of an epoxidic formulation of well determined properties as it
has a marked influence on both structural and external factors.
Temperature and time strongly act on polymers properties owing to their viscoelastic nature.
Knowledge of the dynamic moduli and properties of polymeric materials is indispensable for the design of this materials. At
the same time, the influence of the temperature on polymers behaviour may be studied once the activation energy is known.
In this paper the different dynamic moduli and activation energy are measured using a Perkin Elmer DMA 7.
The relationships between the dynamic mechanical properties and the molecular weight of the polymers make possible the calculation
of the molecular weight.
Results reasonably agree with literature values.
Authors:María Villanueva, Jorge Proupín, José A. Rodríguez-Añón, L. Fraga-Grueiro, Josefa Salgado, and Nieves Barros
The rational and sustainable exploitation of natural resources is one the priority objectives of our consumer society as an unavoidable strategy for survival. In previous articles, research group TERBIPROMAT has established the bases for the elaboration of energy maps of forest biomass. With those data, it is possible to classify the species in terms of their energy content and of their possible application as biofuels following European Norm CEN/TS 14961/2005 on solid biofuels. Main forest species used in this study were Populus and Paulownia. These species have a fast growth and produce big amounts of energetic biomass. To complete this study a comparison with autochthonous forest species, Eucalyptus and Pinus, was made. In this study, a thermogravimetric analysis is employed to qualitative study the resistance to thermal degradation of different forest species. These studies complete those made through static bomb calorimetry, elemental analysis, and different mechanical tests trying to get relationships between thermal behaviour and some physical properties.