Conversion degree composites

Equations 29-32 contain two unknown values y>f (y>j = 1 - y) ) and x- By solving these equations one can find the value of x for any (p2o. Now, the parameters found can be put into Eq. 22, from which the binodal and spinodal may be found in the usual way. The authors [77] have computed conversion degree-composition curves. 

As already mentioned, with regard to the stoichiometry three things have to be determined the end point stoichiometry of the PECs, the degree of conversion (degree of release of counterions), and the overall composition f(X) of the complexes at nonstoichiometric mixing ratios. The methods used for the investigation of the PEC stoichiometry are not very sensitive to the level of aggregation i.e., they are practically the same for soluble PECs and colloidal PEC structures. 

Note K-p is equilibrium constant of a specific reaction x is conversion degree of an initial fluoride UF into UFi i at stoichiometric composition for the specified reaction. 

The composition of NbCls dissociation products in atmospheric-pressure plasma is shown in Fig. 7-76. The initial concentration of NbCls is 3.7 mol/kg. Niobium formation occurs at temperatures exceeding 3700 K. The energy cost of niobium production is shownin Fig. 7-77. The minimal energy cost is 28.3 eV/atom in the case of absolute quenching, which can be achieved at a specific eneigy input of 28.1 eV/mol and conversion degree of 99%. 

Translational temperature To in the non-equilibrium plasma system was not sufficient for effective methane conversion, whereas vibrational temperature was able to stimulate the process. The conversion degree of methane into acetylene achieved in the plasma system is presented in Fig. 9-5 as a function of the specific energy input at three different pressures 10, 40, and 80 Torr. When the pressure increases from 10 to 80 Torr, the methane-to-acetylene conversion degree rises and reaches a maximum of 80% at = 2.6 eV/mol CH4. The gas-product composition in this regime is H2,73 vol % CH4,5 vol % and C2H2,22 vol %. The concentration of ethylene, ethane, and higher hydrocarbons is less than 1% soot production... 

Figure 9-11. Effect of initial methane-nitrogen mixture composition (molar fraction of methane) on formation of HCN discharge power 1.6 kW. Conversion degrees (1) yield of HCN (2) yield of high-boiling-point hydrocarbons.

Controlled variables affecting product quality. The most important of these are MM, MMD, monomer conversion, copolymer composition distribution, copolymer sequence distribution and degree of branching. Those which can be measured should be controlled however, most of these variables also are not measurable on-line. For those variables which are not measurable, all identifiable inputs must be controlled in order to maintain the unmeasured output at a constant value. 

W.C. Brandt, L.F.J. Scheider, E. Frollini, L. Correr-Sobrinho, M.A.C. Sinhoret, Effect of different photo-initiators and light curing units on degree of conversion of composites, Braz. Oral Res. 24 (2010) 263-270. 

R.O. Souza, M. Ozcan, S.M. Michida, R.M. de Melo, C.A. Pavanelli, M.A. Bottino, L.E. Soares, A. A. Martin, Conversion degree of indirect resin composites and effect of thermocycling on their physical properties, J. Prosthodont. 19 (2010) 218-225. 

Kinetic theory was formulated to model the conversion degree of a material from one state to another. At each temperature, a FRP material can be considered as a mixture of materials in different states, with changing mechanical properties. The content of each state varies with temperature, thus the composite material shows temperature-dependent properties. If the quantity of material in each state is known and a probabilistic distribution function accounting the contribution from each material state to the effective properties of the mixture is available, the mechanical properties of the mixture can be estimated over the whole temperature range. 

Figure 3.2 Temperature-dependent conversion degree of glass transition and volume fraction of glassy state (derived from glass transition of an E-glass fiber polyester composite during a dynamic mechanical analysis (DMA) test at a heating rate of5°Cmin and a dynamic oscillation frequency of 1 Hz) [3]. (With permission from SAGE.)...

Figure 4.20 Conversion degrees of decomposition from different thermal loading programs for powdery GFRP composites curves at constant heating rates from TGA and modeling and modeling curve based on ISO fire curve [30]. (With permission from SAGE.)...

In this chapter, the post-fire behavior of FRP composites was evaluated and modeled on the stmctural level. Results from the models compared well with results from fuU-scale post-fire experiments on cellular GFRP beam and column specimens that had been subjected to mechanical and thermal loading up to 120 min with inclusion of different thermal boundary conditions. On the basis of the previously proposed thermal and mechanical response models, existing approaches for post-fire evaluation can be applied. Predicted temperature profiles and the conversion degrees of decomposition can be used to estimate the post-fire stiHhess from existing two- and three-layer models. The borders between different layers can be determined either by a temperature criterion or a RRC criterion. 

Recent years have seen vast experimentation with many different process designs for the liquefaction of coals. The degree of coal conversion and composition of the product oil vary with both the coal rank, maceral composition, mineral matter content, and conversion process. Whereas much attention has been focused on the separation and characterization of the product oil by chromatographic and spectroscopic means, less work has been done on the unconverted or process altered residues from liquefaction processes. Although many of the processes do incorporate some sort of bottoms processing , other possible uses of these residues include road materials, carbon electrodes, coal gasification feedstocks, and as direct combustion fuels. Recently, coal conversion by-products have been used as raw materials in the synthesis of thermosetting polyesters. ... 

From a control standpoint, the most important variables are those which ultimately affect the end-use properties. These will be referred to as controlled variables affecting product quality. The most important of these are MW, MWD, monomer conversion, copolymer composition distribution, copolymer sequence distribution, and degree of branching. Most of these variables are not measurable on-line. The common approach is to control those variables which are measurable, to estimate those which are estimable and control based on the estimates, and to fix those which cannot be estimated by controlling the inputs to the process. Closed-loop control involves the adjustment of some manipulated variable(s) in response to a deviation of the associated control variable from its desired value. The purpose of closed-loop control is to bring the controlled variable to its desired value and maintain it at that point. Those variables which are not controllable in a closed-loop sense are maintained at their desired values (as measured by laboratory or other off-line measurement) by controlling all the identifiable input in order to maintain an unmeasured output at a constant value. 

In the case of copolymers, the composition is also a mean composition that generally reflects the composition of the different co-monomers used in the polymerisation medium after total conversion of the monomers into polymers. However, because the reactivity of monomers between each other can be quite different, the composition of the different molecules of copolymers in a single preparation can vary. Indeed, composition in monomer units of the copolymers formed at the beginning of the polymerisation reaction is not necessarily the same as composition of the copolymers formed at the end of the polymerisation reaction. This effect adds heterogeneity to chemically synthesised copolymers, and the only way to appreciate this effect is to analyse the composition of the polymers at low conversion degree during polymer synthesis. 

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