The effect of the storage of soils on their microbial activity has been studied using a microcalorimetric method. Soil samples
were kept in closed polyethene bags at 4°C during 3–6 months. Results show changes in the slope of the differentP−t curves recorded from the samples stored at 4°C. This fact strongly suggest the existence of changes of the microbial activity
of soil as the heat evolution is a direct measurement of the cells metabolic activity. The value of the Peak-time (time in
which the microcalorimetric signal reaches the maximum value) is related with the microbial density of soil samples. This
parameter was affected by the time of storage increasing with time. The total heat evolutionQ(t), of the soil samples amended with glucose calculated from the area limited by the Power-Time curves, also decreases with
the time of storage. The soil that had been stored for 6 months before experiments, showed the lowest valu ofQ(t).
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.
The thermal degradation of the epoxy systems diglycidyl ether of bisphenol A (BADGE n=0)/1, 2 diamine cyclohexane (DCH) and diglycidyl ether of bisphenol A (BADGE n=0)/1, 2 diaminecyclohexane (DCH) containing calcium carbonate filler immersed and not immersed in hydrochloric acid have
been studied by thermogravimetric analysis in order to compare their decomposition processes and to determine the reaction
mechanism of the degradation processes. The value of the activation energies, necessary for this study, were calculated using
various integral and differential methods. Analysis of the results suggests that hydrochloric acid does not affect the decomposition
of the epoxy network and that the reaction mechanisms produce sigmoidal-type curves for the systems not immersed in HCl and
deceleration curves for the same systems immersed.
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.
Modulated differential scanning calorimetry (MDSC) and dielectric analysis (DEA) have been used to characterize the cure process
of the system diglycidyl ether of bisphenol A (DGEBA(n=0)/1,2 diaminocyclohexane (1,2 DCH). The trans isomer and a mixture cis/trans(30-70% respectively) of 1,2 DCH were used to find their different behaviour. The study allowed to check the influence of
the cisisomer on the thermoset curing process. Gelation times were obtained through the equation proposed by Johari and vitrification
times from the point of inflection of the complex calorific capacity modulus.
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.
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.
Summary Soil productivity and health were analyzed using an experimental procedure designed for this kind of studies. The continuous loss of fertile soil obliged the Food and Agriculture Organization (FAO) to declare soil as an item to be protected as a support of the world society welfare. The procedure here described is in accordance with the premises necessary for a rational and sustainable development of soil and the resources it contains and can be used to study any soil all over the world. The study was carried out using soil microbial population as a bioindicator of soil health. Microbial activity was followed using the microcalorimetric technique. The microcalorimetric study can be complemented through a deep analysis of soil physical, chemical and biological properties together with a study of the environmental properties that have a strong influence on the afore mentioned properties and, thus on the microbial activity in soil. The different properties follow different ASTM, ISS/FAO, USDA, etc. well defined standards. The experimental procedure reported in this work could be very helpful to create a data basis that could be useful to quantify and control soil potentiality or design soil decontamination and recovery systems.
Summary The European policy on energy focus on the search for alternative and renewable sources of energy where forest biomass plays a significant role. In this article, calorific values of different kinds of forest residues (leaves, thin branches, barks, etc.) are reported. These values were measured by combustion bomb calorimetry with the objective of understanding, through different risk indices, the behaviour of forest waste in the case of wildfires, and also to study the use of forest residues as raw materials to be used as energy sources. The study was complemented with determination of elemental analysis, flammability using a standard epiradiator, thermodegradation analysis, and different mechanical tests trying to get relationships between thermal behaviour and some physical properties. The study was carried out on Eucalyptus globulus Labill and Pinus pinaster Aiton, because these forest formations have both high economical and ecological interest in Galicia (NW Spain).