Specific interaction parameter

The application of this model to alkanolamine solutions is not possible directly since the specific interaction parameters (B s) for alkanolammonium ions and carbamate ions are not available. Also the dissociation constant for the simplest amines (MEA, DEA,... 

Knowing the KA and KB values for the fibres and matrices and by analogy with Equation 14, it is possible to define a specific interaction parameter A, describing the acid/base interaction between the fibre (f) and the matrix (m) as... 

Table IV. Specific Interaction Parameter A Between Carbon Fibre and Epoxy Matrix (in Arbitrary Units)...

Specific Interaction Parameter - Reversible Energy of Adhesion (Wp + WA)... 

In contrast, as shown in Figures 8 and 9, there is a very good correlation between the interfacial shear strength X (average or maximum) and the specific interaction parameter A, expressing the acid/base interactions exchanged at the interface. 

Figure 8 Interfacial shear strength t versus specific interaction parameter A for the composites based on resin I.

Alkanes have been used in conjunction with unsaturated and aromatic hydrocarbons to study specific interactions of different surfaces [59-61] in therms of the enthalpy of adsorption. Sidqi et al. [53] defined the specific interaction parameter ... 

Specific interaction parameter was used in the description of the surface properties of activated carbons [62] and pure and composite oxides [63]. 

As stated above, IGC is possibly the most rapid method for the evaluation of 7 and of a specific interaction parameter, Isp, that qualitatively describes the affinity of the solid surface for non specific interactions. London interactions between two partners are proportional to their polarisabilities, to their molecular ionisation potentials, and to the number of elemental volumes of the two phases in interaction. Hence, taking one partner as a molecular probe allows to detect changes that may occur when, for instance, submitting the other partner to heat treatments or chemical transformations. 

Alternatively, one may use the Guggenheim equation (Equation 1.28), which is rigorously correct for solutions of mixed electrolytes. In this equation, the specific interaction parameters are moved from the denominator to a second term, in which b is an adjustable parameter. 

The accuracy of the measurements was equal to 0.001 min for the retention time, 0.1 °C for the column temperature, 20 Pa for the atmospheric pressure, and 100 Pa for the pressure drop. Therefore, net retention volumes were known with a precision of about 5%. Consequently, the absolute error for free energy of adsorption and for the specific interaction parameter are estimated to be 0.1 and 0.2 kj/mol, respectively. 

Specific Component of the Surface Free Energy of Heat-Treated Silicas. Specific interaction capacities of heat-treated silicas, that is, their ability to interact with polar molecules, were examined with chloroform (Lewis acid probe) and toluene and benzene (amphoteric molecules). Figure 2 provides examples of the evolution of the specific interaction parameter Zsp of the different silicas with chloroform as a probe. 

Specific interaction parameters are strongly reduced upon surface modification (hexadecylated silicas have Zsp values close to zero). In methanol-reacted silicas, Zsp values decrease when heat-treatment temperature increases. This result suggests that after grafting with methanol, some free hydroxyls are still available for further interactions. This scenario is... 

In the second step, with the hydrolysis constants and the specific interaction parameter for ZrOH" and for Zr3(OH) fixed to the values optimised as detailed above, the equilibrium constants and interaction parameter for all other species in the overall hydrolysis model were obtained by a global fit of the potentiometric, solubility, solvent extraction and ion exchange data mentioned above. The fit was extended to the determination of equilibrium constants for heterogeneous reactions ion exchange constants, solubility constants and liquid/liquid distribution coefficients. The fit was based on a preselection of the stoichiometries of dominant species which included invariably the species Zr(OH)4(aq), Zr ) ), Zr (OH)Jj and Zr4(OH)i6(aq) and various other mono-, di-, tri- and tetravalent species to improve the fit. The potential formation of chloride complexes of Zr was considered for chloride containing solutions, using the stability constants determined in Section V-4. If all fitted results were found insensitive to the equilibrium constants of a given species, the respective species was removed from the list of species. 

The specific interaction parameter b is also different from the corresponding Ae value because of the different Debye-Htickel terms. Up to the review of Baes and Mesmer [1976BAE/MES], there were no data available to model the ionic strength dependence of the equilibrium constants for polynuclear species in one of the ionic media. The common method to estimate equilibrium constants at zero ionic strength was to use an experimental value at finite ionic strength and then to use only the Debye-Htickel term to estimate the value at zero ionic strength. 

FIGURE 31.2 Evolution of the specific interaction parameter of silicas with chloroform versus heat treatment temperature. 

Fiber-Matrix and Filler-Matrix Specific Interaction Parameters... 

Figure 12 Interfacial shear resistance r versus specific interaction parameter Isp for C fibers and an epoxy matrix (DGEBA-DDS). The C fibers were (1) untreated, (2) oxidized, (3) sized, and (4) commercial sized PAN-based fibers. The epoxy matrix was a diglycidyl ether of bisphenol A with 35 parts by weight of diamino diphenyl sulfone (DGEBA-DDS). (Reprinted from Ref. [95].)...

Figure 13 Adsorbed amount of a polyester resin (used as a dispersing agent for pigments and fillers) onto organic and mineral pigments versus the pair specific interaction parameter I p defined in Eq. (41). (Reprinted from Ref. [94].)...

Several interesting observations relate to such thermodynamic measurements. For example, the exothermic effects, associated with phase separation in LCST-type polymer blends, showed a correlation between the exothermic enthalpy and the interactions between the components (Natansohn 1985) however, the specific interaction parameter xn was not calculated. In another example, there are definitive correlations between the thermodynamic and the transport properties (see Chap. 7, Rheology of Polymer Alloys and Blends ). Thermodynamic properties of multiphase polymeric systems affect the flow, and vice versa. As discussed in Chap. 7, Rheology of Polymer Alloys and Blends , the effects of stress can engender significant shift of the spinodal temperature, AT = 16 °C. While at low stresses the effects can vary, i.e., the miscibility can either increase or decrease. 

More recently, it has been shown, in particular by Fowkes and co-workers [2,6,7], that electron acceptor and donor interactions, according to the generalized Lewis acid-base concept, could be a major type of interfacial forces between two materials. This approach is able to take into account hydrogen bonds which are often involved in adhesive joints. Inverse gas chromatography at infinite dilution for example is a well adapted technique [8-10] for determining the acid-base characteristics of fibres and matrices. Retention data of probes of known properties, in particular their electron acceptor (AN) and donor (DN) numbers according to Gutmann s semi-empirical scale [11], allow the determination of acid-base parameters, and Kj), of fibre and matrix surfaces. It becomes then possible to define a "specific interactions parameter" A at the fibre-matrix interface, as the cross-product of the coefficients and Kq of both materials [10,11] ... 

More recent work [10] has shown that, for systems of untreated and surface treated carbon fibres in two types of epoxy resin, linear relationships (Figure 1) exist between the interfacial shear strength x and the specific interaction parameter A, defined... 

From the equation 4 it follows that the negative value of parameter x 12 is necessary to obtain a stable homogeneous poljuner blend. The negative value of X12 is characteristic of systems with specific interactions such as dipole-dipole or hydrogen bond interactions (1,5,6,17). A schematic representation of the temperature dependence of a specific interaction parameter, according (13), is given in Figure 1, curve 3. 

Fig. 16.9 Determination of the specific interaction parameter, PP, for polar probes on AI2O3 at 250 °C (adapted from Ref. [32])...

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