Rheokinetic rheological

This chapter reviewed the chemistry of ring opening polymerization of cyclic monomers that yield thermoplastic polymers of interest in composite processing. In addition, this chapter focuses on the chemistry, kinetics, and rheology of the ring opening polymerization of caprolactam to nylon 6. Finally, these rheokinetics models are applied to the reactive injection pultrusion (RIP) process. 

The main rheokinetic problem consists of the determination of the time dependence of the degree of conversion (3(t) and the correlation between (3(t) and the changes in the rheological properties of the reactants. One possible kinetic function (3(t) was discussed in Section 2.2. In considering the rheological properties of the reactive medium, we can neglect non-Newtonian... 

A complete analysis of the role of the radial distributions of all the parameters that determine the flow through a tubular reactor during polymerization is a very complicated, and it is doubtful whether general solutions can be found. However, solutions can be obtained for various situations for a system with known kinetic and rheological properties, because we will be searching for specific details rather than for a general physical picture of the process. It is also possible to carry out a general analysis at certain simplified models, which nevertheless include the principal rheokinetic effects. 

Among physicochemical methods for studying curing processes, rheokinetics is the closest to calorimetry, also yielding combined characteristics of the chemical dynamics of the process. Due to this, there was carried out a comparison of quantitative curing parameters obtained by rheological and calorimetric methods. 

The rheokinetic degree of conversion means a conversion dependent parameter measurwl by a rheological method. 

When the time changes are characterized by rheological methods the apparent autocatalytic shape of (t) may be generated by a non-linear dependence of the rheokinetic parameter on / . For instance, it can be shown that, if p is the storage modulus G, G is proportional to the concentration of elastically active... 

We think that it is an urgent matter to solve concrete problems taking into accoimt all possible peculiarities different empirical relationships (rheological, kinetic), different geometry, various types of representing boundary conditions, organization of heat and mass transfer, etc. The absence of investigations of the effect of non-Newtonian properties of a liquid on the flow mechanisms of rheokinetic media seems to be a gap in the field of theoretical analysis. 

To optimize the pre-reaction a detailed understanding of the polymerization kinetics and resulting changes of material properties is necessary. As it is mentioned before, the chain growing will increase the viscosity of the polymer. A novel approach to combine the rheology with kinetics is called rheokinetics and is the subject of discussion in the following second chapter. 

The change of rheological properties of reaction systems is determined by two main factors kinetic features and rheological properties of initial and forming components. To establish the conditions of gel formation during reaction, both the kinetics of reaction and the rheokinetics were studied [119,319]. Simultaneous semi-IPNs produced from cross-linked PU... 

These results show that the evolution of the system in the course of its formation seem to be important from the point of view of understanding the real kinetic conditions of IPN formation and phase separation. Rheokinetic data allow us to study various structural states (from a rheological point of view) in different time periods of the reaction. Of course, the discussion given here is over-simphfied because it is difficult to separate pure kinetic effects that influence the viscosity and viscoelastic behavior from effects connected to simultaneously proceeding microphase separation. 

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