This chapter highlights the importance of chemorheology in determining cure properties of reactive systems. A brief introduction to experimental rheology has been provided in Chapter 3 to provide a baseline knowledge of experimental rheology. In this chapter we examine a description of chemorheology in terms of basic chemorheology, chemoviscosity, gelation and vitrification transitions and ultimate properties. Finally, examples of chemorheological analysis will be discussed. (We will briefly summarize chemorheological data and models in this chapter, but only for reference to chemorheological testing. A more extensive examination of chemorheology and modelling of systems will be presented in Chapter 5.)
The definition of chemorheology (in this text) is the study of the deformation properties of reactive polymer systems. Figure 4.1 shows a schematic representation of the structural development during thermoset cure.
Step (a) shows unreacted monomers, and cure proceeds to step (b), at which there is the formation of some branched molecules. By step (c) the cure has progressed to the gel point, such that an infinite network is formed across the whole structure. Further cure can occur to point (d), at which the material becomes fully cured and vitrification is reached.
The essential elements of a chemorheological study are
ultimate chemorheological properties
We shall focus on modelling in Chapter 5.