Thermal properties bentonite

Table 2 shows the properties used for the coupled analysis. Thermal properties are the same for rock mass and bentonite. It is assumed that the repository consists of bentonite having very low permeability. To examine the uncertainty of up-scaling process on the performance assessment, the cases shown in Table 3 are examined. 

Othman, N., Ismail, FI., and Mariatti, M. 2006. Effect of compatibilisers on mechanical and thermal properties of bentonite filled polypropylene composites. Polymer Degradation and Stability... 

However, the mechanism of action of filtration control additives is not yet completely understood. Examples are bentonite, latex, various organic polymers, and copolymers. Many additives for fluid loss are water-soluble polymers. Vinyl sulfonate fluid loss additives based on the 2-acrylamido-2-methyl-propane sulfonic acid (AMPS) monomer are in common use in field cementing operations [363]. The copolymerization of AMPS with conjugate monomers yields a fluid loss agent whose properties include minimal retardation, salt tolerance, high efficiency, thermal stability, and excellent solids support. 

This report presents our approach for calculation of the Task. Our numerical code THAMES is the three-dimensional finite element simulator of fully coupled processes. First, we defined the input data for THAMES from the supplied properties of FEBEX bentonite. After calibrations of some parameters such as thermal vapour diffusivity, the analysis that treats fully coupled thermal, hydraulic and mechanical processes was carried out. 

First, we identified the input parameter for THAMES on properties of FEBEX bentonite, because the fundamental properties of FEBEX bentonite had been obtained by various laboratory tests to identify the input data for the numerical code CODE BRIGHT (enresa (1998)). After calibrations of the all required parameters for THAMES, such as thermal vapour flow diffusivity and intrinsic permeability, the coupled THM simulations were carried out. 

Abstract Geological disposal of nuclear fuel wastes relies on the concept of multiple barrier systems. In order to predict the performance of these barriers, mathematical models have been developed, verified and validated against analytical solutions, laboratory tests and field experiments within the international DECOVALEX project. These models in general consider the full coupling of thermal (T), hydrological (H) and mechanical (M) processes that would prevail in the geological media around the repository. This paper shows the process of building confidence in the mathematical models by calibration with a reference T-H-M experiment with realistic rock mass conditions and bentonite properties and measured outputs of thermal, hydraulic and mechanical variables. 

The considered radial process in the bentonite annulus is a complicated one with coupled, highly nonlinear flows that involve many things. There are liquid flow and vapor flow as well as conductive and convective heat flow depending on gradients in pressure, water vapor density and temperature. The flow coefficients depend on water properties such as saturation water vapor pressure and dynamic viscosity of water. They also depend on the properties of bentonite water retention curve, hydraulic conductivity and water vapor diffusion coefficient, and thermal conductivity, all of which are functions of degree of water saturation. 

We report here preliminary results of the physicochemical characterization of a composite material obtained by combining the cethyltrimethylammonium cations clay insertion procedure with the room temperature synthesis of mesoporous materials inside of clay layers. The Romanian bentonite, containing 64% montmorillonite was used. The organic cations are incorporated within the interlayer region of the clay, serving to prop of>en the layers and to allow incorporation of the silicon source for MCM-4I synthesis. The obtained materials display a high thermal stability and molecular sieve properties. 

Stability can be said as the protection of polymeric materials from which lead to deterioration of properties [9]. In literature, there are different and sometimes contradictory reported papers concerning the effect of the nanoparticles on polymer thermal stability. There are papers suggesting that nanoparticles have no obviously effect on thermal stability, some of them suggested a small to substantial enhancement and some others suggested acceleration of thermal decomposition. In a study performed by Ollier et al. [10], the author incorporated 5 % weight of bentonite in unsaturated polyester (UP) matrix. They noted that the addition of bentonite... 

The group of Gu Z. in the 2009, reported the behavior of styrene butadiene/ rubber/organo-bentonite nanocomposite prepared from latex dispersion, content was lower than 12 mass%. The results showed were that presence of organo-bentonite in the nanocoposite affects direct in the thermo stability, mechanical properties and swelling behavior, which was attribute to the good barrier properties of the dispersed nanoparticles. The dispersion is an important factor that can affect various properties such as thermal stability [81]. 

Burns et extracted from soil, clay-free material with urease activity equivalent to about 20% of that of unextracted soil. Partial separation of brown-coloured humic compounds from the extracted ureases could be achieved with little loss of enzymic activity. The extracted soil urease retained activity when incubated for 24h with Pronase, whereas this proteinase was sufficiently stable in the presence of soil to demonstrate the destruction of added jack bean urease. Pronase action also markedly decreased the activities of complexes of bentonite and jack bean urease but was ineffective against a bentonite-urease-lignin complex. The persistence of urease activity in soils was attributed to the formation of exocellular urease-organic colloidal complexes, which permitted reaction between enzyme and substrate and diffusion of products, but which protected ureases from attack by soil proteinases. Further studies by Pettit et compared the properties of extracted ureases, soil ureases and jack bean urease respectively. Km values were influenced by the type of buffer used. Ureases of soil extract had the highest Km value and were the most stable to thermal... 

Here poly(ethyl aerylate) (PEA)/clay nanocompsite as the first example of rubbery polymer/elay nanocomposite synthesized by in situ emulsion polymerization is reported. The clay used is bentonite having extremely strong swelling characteristies in water. The resulting nanocomposite emulsion is directly cast to form film without coagulation process. This study focuses on microstructure, thermal and meehanical properties, and gas barrier permeability of the final PEA/clay nanoeomposites. 

Table 6.1 Properties of thermal degradation of P EA/bentonite nanocomposites...

Transparent exfoliated-intercalated PEA/bentonite nanocomposites are prepared by in situ emulsion polymerization in aqueous dispersions containing bentonite, following directly casting the resulting emulsion into film. XRD and TEM reveal that disorderedly exfoliated silicate layers and intercalated silicate layers coexist in the PEA matrix. Thermal stability, mechanical properties and barrier properties of the obtained materials were greatly improved. Because relatively small amounts (<10%) of nanometer-size clay particles can provide large... 

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