Swelling kinetic curve

Fig. 2. Swelling kinetics curves for ( ) MMA/DMA 70/30 and (Q) EMA/DMA 70/30 gels at pH 7.0 in 0.01 M citrate. I = 0.10 set by addition of Nad. T = 25 °C. Curves drawn to guide eye. Reprinted with permission from Ref. 5. [Copyright 1988 American Chemical Society.]...

This snbchapter presents the results of theoretical and experimental studies on the influence of solvent properties on the nature of the swelling kinetics for elastomeric polymer networks at finite strains of the polymer matrix. Emphasis is focused on the study of the relationship of the asymptotic properties of the swelling kinetic curves with the thermodynamic quality of a solvent. The chemical potential of a solvent in the sample under swelling is given by the following equation ... 

In the case of a poor solvent Uj 1. Swelling kinetic curves are described by the law of normal sorption (x > 0.5). When x < 0.5 swelling curves are S-shaped ones. Kinetic curves of swelling of a sample in a good solvent shown in the coordinates (a/x g) are S shaped, and their initial region described by equation [6.6.1] with the parameter q > 0.5. 

Figmes 6.6.1 and 6.6.2 show the results of numerical solution of the boundary problem for a variety of solutions of x One can see how the nature of the diffusion process and the shape of swelling kinetic curves changes depending on the deterioration of the thermodynamic quality of solvent. Particularly, it can be seen that as the parameter Floiy-Huggins increases the interval of the boundary concentration decreases, and swelling kinetic curves transform to kinetic curve of the normal sorption. 

Figure 6.6.4 shows the results of a study of the kinetics of absorption of low-molecular-mass liquid by polymer. It can be seen that all swelling kinetic curves plotted in the coordinates ( /t g), have an initial linear stage, i.e., kinetic curves are normal sorption ones. Consequently, the experimental values of the diffusion coefficient D, can be calculated using equation [6.6.8]. Figure 6.6.5 shows the swelling kinetic curves plotted in the coordinates (t -ln(l - g)). They take the shape of straight lines with a slope coefficient k at... 

Figure 18c displays swelling kinetics of two SV films with the same initial thickness but different microphase-separated structures. The curves show up to 10% larger swelling (smaller poi) of SV films with the initial bulk lamella morphology as compared to the films with the non-bulk micelle phase [119],... 

There are two modifications to the described method. The first one presupposes deposition of the coating in Cl vapor, which is at the same time a solvent of the coating material. To this class of materials belong some Cl, and grades IFHAN and VNH-L. According to the second method swelling of the polymer is exercised in the mixture of two vapors that of Cl and polymer solvent compatible with it. Analysis of Fig. 2.35 with kinetic curves of Cl evaporation has proven that many Cl can be used within this technology. 

Restricting ourselves to the first term of a series Eq. [6.1.42], we can write for the final swelling stage the equation of kinetic curve... 

The above expressions allow us to describe the shape of kinetic curves gi(t) in general terms. In particular, as it follows fromEqs. [6.1.39] - [6.1.41] atq< 1, the kinetic curves in the coordinates (t,gi) are upward convex and have the shape typical for pseudo-normal sorption. This takes place at slinear mode of liquid absorption. At s>Se/2-l the lower part of the kinetic curve is convex in a downward direction and the whole curve becomes S-shaped. Note that in terms of coordinates (t ,gi) at s > 0 all the kinetic curves are S-shaped. Hence, the obtained solutions enable one to describe different anomalies of sorption kinetics observed in the experiments on elastomer swelling in low-molecular liquids. 

Figure 6.1.2 gives the results of numerical solution to problems of Eq. [6.1.25] with diffusion coefficient defined by Eq. [6.1.35]. The kinetic curves of swelling at different values of s are depicted in Figure 6.1.3. ... 

Figure 6.1.3. Kinetic curves of plane layer swelling at different values of concentration dependence of diffusion coefficient (e=0.1,d = 2/9) a - power law mode (l-s = 0 2-s=l 3-s = 1.5 4-s = 2.5) b - exponential (5 - s = 5) and blow-up mode (6 - s = 5.5). [Adapted, by permission, from E. Ya. Denisyuk, V. V. Tereshatov, Vysokomol. soed., X42,74 (2000)].

Figure 3.327. (a) Kinetic curves of swelling for the polyurethane elastomer supposed to static fatigue and accelerated fatigue [207] 1) unstressed 2) =... 

This arises in polymer/permeant systems which obey Fickian diffusion (described later in Section 20.4). The rate of diffusion of permeant molecules is much less than the polymer segment mobility. Under these conditions, the rate at which sorption equilibrium is approached is independent of swelling kinetics. As shown in Figure 4, the sorption curve vs, t ) is linear in the... 

The kinetic curve is an integral characteristic of the swelling process... 

Figure 6.6.2. Theoretical kinetic curves for swelling of Figure 6.6.3. The experimental kinetic curves of a flat layer at different values of the Flory-Huggins PDUE samples swelling in solvents of different ther-...

---