Ziegler-Natta polymerization decay period

Ziegler-Natta polymerizations in that their particular shape may be characteristic of a particular catalyst or catalyst-monomer system. In general, such profiles can be considered to consist of three periods, viz., an acceleration period, a stationary period, and a decay period. Some catalyst systems show all three types. 

In the build-up period of the decay-type Ziegler-Natta polymerization of propylene, the rates are found to be different when propylene is introduced after TiCls and AlEts are allowed to equilibrate from the case when AlEts is added after the gas in introduced. The rates in the former case are given by the expression... 

In Ziegler-Natta polymerizations, the reaction systems are more often heterogeneous than homogeneous. While the relatively few polymerizations that are homogeneous behave in a manner generally similar to ionic polymerizations, described in Chapter 8, the heterogeneous systems usually exhibit complicated behavior, as can be seen from some typical kinetic rate-time profiles of Ziegler-Natta poymerizations. Types (a)-(f) in Fig. 9.5. The shapes of these profiles may be characteristic of particular catalysts or catalyst-monomer systems and may be considered to consist of three periods, viz., an acceleration period, a stationary period, and a decay period. Some catalyst systems, however, show all three types. 

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