Superimposed processes of polymerization and crystallization

In the general formulation the reactive processing model (Section 2.1), it was stressed that different phenomena occurring during a process cycle may be superimposed and that may be mutual influence between the various processes. Superposition of polymerization and crystallization is of particular importance, because it always occurs when a crystalline polymer is synthesized below its melting point. It is especially convenient to study this effect for anionic activated polymerization of e-caprol- 

Two typical cases are illustrated in Fig. 2.24 the first scheme (Fig. 2.24 a) is related to high-temperature polymerization, in which newly formed polymer is molten and the processes of polymerization (part Ob of the full curve) and crystallization (part bK of the full curve) are separated in time. The second case (Fig. 2.24 b) illustrates low-temperature polymerization in this situation crystallization starts before the full process of polymerization is completed. This is typical superposition of two kinetic processes, and the shape of the curve in Fig. 2.24 b does not allow the separation of these processes without additional information and assumptions.The net heat effect is the same in 

A typical example illustrating the separation of the net heat effect AT into parts corresponding to polymerization ATP and crystallization ATC is shown in Fig. 2.25.100 These data were obtained by direct measurement of the quantities of polymeric products formed during the reaction. This gives us the value of ATP calculated from(3(t) and the known value of the maximum temperature increase dur- 

Modelling of crystallization was discussed in Section 2.8. Now, we shall develop a model for superimposed polymerization and crystallization processes. This model is important for calculating temperature evolution during reactive processing, because an increase in temperature, regardless of its cause, influences the kinetics of both polymerization and crystallization. This concept is expressed by the following equation for the rate of heat output from the superimposed proceses 102,103 

The most important feature of this model is the introduction of the factor P(t) into the second term on the right-hand side of Eq. (2.55). This factor reflects the hypothesis stated above about crys- 

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Theoretical modelling and analysis of the results for the superimposed processes of polymerization and crystallization was carried out for wave propagation in anionic activated reaction of e-caprolactam polymerization.258 In the steady situation, the process is described by the system of differential equations ... 

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