2DPP+HCE

Figure 10.2 The chemical structure of the epoxy polymer 2DPP + HCE/DDM...

Two basic distinctions of curves a(t) for the studied systems attract our attention, hirst, for the system 2DPP+HCE/DDM, the smooth decrease of a slope of curves a(t) is observed... 

Figure 10.8 Dependences (1-a) of reaction time (t) in logarithmic coordinates corresponded to Equation (10.7) for systems 2DPP + HCE/DDM (1) and EPS-l/DDM (2).

Figure 10.10 Comparison of experimental (1) and calculated values of a relationship (10.1). (2) kinetic curves a(t) for system 2DPP + HCE/DDM.

Figure 10.14 Dependence of a degree of conversion a, on time of reaction t, in double logarithmic coordinates corresponding to Equation (10.1) for system 2DPP + HCE/DDM at 353 (1), 373 (2) and 513 K (3).

Table 10.1 The dependence of time of achievement of the first gelation point from curing temperature T for system 2DPP+HCE/DDM ...

Figure 10.15 A correlation between viscosity of reaction medium rig and fractal dimension of microgels D for system 2DPP + HCE/DDM.

The combination of Equations (10.13) and (10.14) allows the estimation of the value The comparison of experimental and theoretical dependencies of the gelation time for its first point of appearance from the fractal dimension of microgels D for system 2DPP + HCE/DDM is given in Figure 10.16. 

Two main distinctions of curves for the indicated systems attract our attention. Firstly, for system 2DPP+HCE DM the smooth decrease of a slope of curves is observed in the process of increase t, whereas for system EPS-4/ DDM the linear dependence up to the large (about 0.8) values Q is observed. Secondly, if the limiting conversion degree of curing reaction for the system 2DPP+HCE/DDM is the function of T (the more T the more this degree), then for the system EPS-4/DDM such dependence is not present and at all used T maximum value Q is observed, close to one. 

Now it is possible to calculate value using the reaction rate constants k, obtained according to the described above experimental methods as function of t or Q. The calculation has shown the principal distinction of behavior D, which is the microgels structure characteristic, for the systems 2DPP+HCE/DDM and EPS-4/DDM. For the first from the indicated systems the value D. does not depend on t at the initial part of the curve but is the function of Tcur. So, at T = 353 and 373 KD, 1.5, atT = 393 D. 1.7andatT = 513 KD, 2.3. It means... 

The authors of papers [26-28], using the determined from slopes of corresponding linear plots of Figs. 5 and 6 coefficient A and B values, described theoretically kinetic curves with the aid of the Eqs. (86) and (87) of Chapter 1 for the systems 2DPP+HCE/DDM and EPS-4/DDM, respectively. The comparison of the calculated by the indicated method and experimentally received curves for both considered systems is adduced in Fig. 9. As it follows from the shown in Fig. 9 plots, the theory and experiment good correspondence was obtained. 

FIGURE 11 The dependence of microgels fractal dimension on curing reaction duration t for the system EPS-4/DDM. The condition D(.= const for the system 2DPP + HCE/DDM was shown by a shaded line. 

As it was noted above, for analysis of polymerization reactions in general and cross-linked polymers curing reactions in particular a number of physical conceptions can be used, from which two of them will be considered below. The indicated conceptions were used as basic relationships of the Eq. (26) and (86) of Chapter 1. In Fig. 16, the dependences of In (100-Q) on t in lo rithmic coordinates, corresponding to the Eq. (86) of Chapter 1, are adduced for the system 2DPP + HCE/DDM at six T values, where Q is given in percentage. 

As it follows from the adduced in Fig. 16 plots, the dependences [In (100-Q)] (t) proved to be linear, i.e., corresponding to the Eq. (86) of Chapter 1. This means that the system 2DPP + HCE/DDM curing reaction at all used T can be considered as classical reaction of the first order, proceeding in medium with small density fluctuations [17], The plots linearity allows to determine the coefficient A value in the Eq. (86) of Chapter 1 from their slope. It is easy to see from the data of Fig. 16 that T inerease results to A growth. Therefore in Fig. 17, the dependence of Aj 2 on T for the studied system is adduced which is approximated well enough by linear correlation and it can be expressed analytically as follows [34] ... 

FIGURE 17 The dependence of parameter on curing temperature for system 2DPP+HCE/DDM. 

The temperature T = 253 K in the Eq. (9) corresponds to the condition A = 0 (see Fig. 17) and this means that at all T < T the system 2DPP+HCE/DDM curing reaction does not occur. The comparison of coefficient A values, determined from linear plots of Fig. 16 A and calculated according to the Eq. (9) Aj, was adduced in Table 1, from which their satisfactory correspondence follows. 

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