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- Author or Editor: J. Rodríguez-Añón x
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Abstract
The thermal degradation of the epoxy system diglycidyl ether of bisphenol A (DGEBA n=0) and m-xylylenediamine (mXDA) containing different concentrations of polyhedral oligomeric silsesquioxanes (POSS) nanoparticles was studied by thermogravimetric analysis in order to determine the influence of both, the POSS concentration and the curing cycle on the degradation process and to compare it with the results for the non modified system. Glass transition temperatures for the same systems were also determined by differential scanning calorimetry. Different behaviors have been observed, depending on the POSS concentration and on the curing selection.
Abstract
Differential scanning calorimetry was applied to assess on seasonally soil organic matter changes. Soils were collected in two sites located in Viveiro (Galicia, Spain). One of them has been used as arable land and the other one was under pinewood. Soil samples were seasonally collected during a year. The heat of combustion and the ignition temperature of the soil organic matter were calculated by analyzing the thermograms obtained by differential scanning calorimetry. The shape and the maximum and end temperatures of the two exothermic peaks observed in the thermograms, yielded information about the relations between the labile and recalcitrant pools, and hence information about carbon stabilization degree in both soils.
Abstract
Calorific values and flammability changes during a year for forest waste originating from silviculture task in Galicia (NW Spain) are reported. These waste materials are becoming to be used as alternative fuels. The present study was made on several hardwood forest species. These forest species occupy nowadays approximately 30% of the total forest surface of Galicia. Calorific values were measured by static bomb calorimeter in an oxygen atmosphere. Flammability was determined using a standard epiradiator. Simultaneously, some other parameters such as elementary chemical composition, heavy metal contents, moisture, density, ash percentage after combustion in the bomb, and main bioclimatic characteristics, were also determined.
Abstract
This paper shows an application of bomb calorimetry used in the procedure of regeneration of waste industrial mineral oils. Using the treatment here reported a recovery of nearly 50% of the used oils was achieved. Furthermore, the oils so recovered contain concentrations of potentially contaminant elements far below the requirements of the European Union (EU). Generally speaking, it can be said that the used oil treatment is based on the proper combination of two main procedures, namely the addition and mixture of certain chemicals-precipitant, flocculant and demulsifying agents- in a permanently stirred reactor, at high temperature, and the centrifugation of the mixture. This oil, recovered through the technique of oil regenerating, cleaning, and fitness, can be used either as a raw material for the elaboration of new oils or as a fuel to be used for cogeneration of thermal or electric energy. The treatment described is highly remunerative, both as regards to cost -used oil is subject to a low-cost process, especially if compared to its elaboration from raw materials- and as regards to ecology, since it is recycled, thus saving a great amount of raw materials.
Abstract
The rheological behaviour of the materials diglycidil ether of bisphenol A (n = 0), 1, 2 diamine-cyclohexane and the epoxy reactive diluent vinylcyclohexane dioxide have been studied both separately and mixed before the beginning of the curing reaction. Different kinds of tests such as: preshear and time sweep, flow curve and stress sweep experiments were carried out. From these experiments, interesting information about: viscosity-shear stress and viscosity-shear rate dependences, storage modulus and the linear viscoelastic region were found out. Relationships between concentration of diluent and the final viscosity of the mixed sample and also between percentage of diluent and storage modulus were studied.
Abstract
This work is a ‘historical’ revision of the evolution of an experimental procedure developed by Prof. Lisardo Nez and his research group TERBIPROMAT to study the sustainability and the soil health state. From the very beginning, in 1993, the microbial activity was the main bioindicator selected to analyse the ‘soil health state’. For this reason, a microcalorimetric technique was used lately to analyse the influence of different human activities such as reforestations, agricultural exploitation or pollution on the microbial activity in different soils. Microcalorimetry is the main scientific technique used in this research to follow the stimulation of the microbial activity by addition of glucose. The data obtained were complemented by a study of physical, chemical and biological parameters of soil and allowed to follow the microbial activity in soils of Galicia (Spain) along the year. The final results, still in revision, will be helpful in establishing a data basis for real maps of the ‘health state’ of different soils. Such maps could be used to design processes that help us to decide how we should exploit soils ensuring their sustainability.
Abstract
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.
Abstract
Isothermal and Differential Scanning Calorimetry is applied to analyze the evolution of soil using its microorganisms and organic matter as bioindicators of soil quality. This study was carried out with two similar soils under different agricultural activities: culture and pasture. Sampling and measurements were performed through 1 year in order to check the sensitivity of common calorimetric indicators of microbial activity and organic matter to the different climatic seasons in the sampling place: spring, summer, fall and winter. Results show that these indicators are sensitive to changes related to climatic conditions but the variability depended also on the nature of the soil: pasture or agricultural land. The results achieved through the present study show that the procedure here proposed could be used on any soil everywhere, providing the determination of the own parameters of soil and zones.
Abstract
The diffusive, calorimetric and thermal degradation behavior of different epoxy-amine systems was investigated during water sorption at different temperatures (23, 40 and 70°C). Experimental results showed that the water absorption at these temperatures fitted well to Fick’s law. Influence of water immersion during different periods of time on the glass transition temperatures was studied by differential scanning calorimetry. Thermal degradation of saturated samples was studied by thermogravimetric analysis. Dependence on the selected curing cycle was also checked.
