DDM:EPS

Kinetics of curing of a haloid containing diepoxide based on hexachlorobenzene has been studied. This oligomer (EPS-1) was cured by 4,4 -diaminodiphenylmethane (DDM) in the stochiometric ratio DDM EPS-1. Haloid containing epoxy polymer with conditional designation EPS-l/DDM has the chemical structure shown in Figure 10.1. 

The curing kinetics of system EPS-l/DDM was studied by a method of reverse gas chromatography (RGC) [29]. The basic parameter received from processing of the experimental data, was the constant of reaction rate k determined for an interval of conversion degrees a = 0.1-0.7 of the kinetical curve degree of conversion-time (a-t). For the determination of k the standard procedure was used the dependences, a, on the reaction time t, as lg[a/(l-a)]=/ (t) which have appeared linear were made. Then the value k (see Equation (10.4)) was determined from a slope of these linear diagrams. Ketones (metyl ethyl ketone, 1,4-dioxane, cyclohexanone) were chosen as the standard substances for the determination of retention time with argon as the gas-carrier. 

Figure 10.6 Kinetic curves a(t) for system EPS-l/DDM at curing temperatures 383 (1), 393 (2) and 403 K (3). The arrows point to the first gelation point...

Figure 10.7 Comparison of experimental (1, 4) and theoretical (2, 3, 5) kinetic curves for system EPS-l/DDM. 1 experimental curve for T ur= 383 K 2 calculation of a relationship (Equation 10.1) under condition of D = Constant = 1.76 3 calculation of a relationship (Equation 10.1) under condition of D = constant = 2.24 ...

The attempts to linearise the dependence (1 - a) on t for system EPS-l/DDM with the use of Equations (10.8) and (10.9) have not resulted in success. It means that the pointed nonhomogeneous reaction proceeds in the reaction medium with large fluctuations of density, but it is not described by the Equations (10.8) and (10.9) for low-molecular substances. Thus, the assumption about the connection of curing reaction type with a level of fluctuation of density of reaction medium is confirmed. 

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 10.9 Dependence (1-a) of parameter t D+2) logarithmic coordinates corresponding to the Equation (10.8) for system EPS-l/DDM.

It follows from this comparison, that good agreement between the theory and experiment results is obtained (the use of logarithmic scale for tj was used for reasons of convenience). In Figure 10.6, the kinetic curves a(t) at three values T for system EPS-l/DDM are shown, in Figure 10.17, the comparison of dependences of peak height of IGC h(t) and curve a(t) for T = 403 K. 

Figure 10.17 Kinetic curve a(t) (1) and dependence of height h of IGC on reaction time (t). (2) for system EPS-l/DDM, curing at = 403 K.

Figure 10.18 Kinetic curves a(t) of the process of curing for systems EPS-l/DDM (1)...

Figure 10.19 Dependence of the fractal dimension of microgels, D, on the reaction time, t, for system EPS-l/DDM. The broken line shows the condition D = constant for...

Figure 10.20 Correlation between the characteristic of auto-acceleration (autostopping) c (or ) and difference AD for system EPS-l/DDM...

The curing temperature of system EPS-l/DDM was 393 K. Values of fractal dimension D of microgels varied within the limits of 1.61-2.38 [1]. 

Figure 13.2 Dependence of (1 - Q) from parameter t AD+2) logarithmic coordinator according to equation (13.7), for system EPS-l/DDM...

DDM which also has appeared to be linear. Together with the previously stated reasons, the data of Figure 13.2 assume that the curing reaction of system EPS-l/DDM proceeds in fractal space with dimension Dj. We should note that att = 3xl0 sa deviation is observed (given in Figure 13.2) of dependences on linearity. From the comparison with the data of Figure 13.1 it is seen that this deviation corresponds to Dj = 3, i.e., transition to nonfractal behaviour at D[ (=d, as should have been expected. 

The obtained results allow one to perform the system EPS-l/DDM curing kinetic analysis within the framework of irreversible aggregation models [160]. In general case the relationship between and R can be written as follows [160] ... 

FIGURE 62 The dependence of reaction rate constant on microgels diameter 2R for system EPS-l/DDM. 

FIGURE 64 The dependences ofnicrogels self-difihsivity D on curing reaction duration t in Euclidean (1) and fractal (2) spaces for system EPS-l/DDM. 

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