Phase Separation and Rheological Behavior of Thermoplastic-Modified Systems

Phase Separation and Rheological Behavior of Thermoplastic-Modified Systems 

Compared to rubber, thermoplastic-modified systems show a much more complicated phase separation and structure evolution, and consequently very few studies were initially undertaken related to phase separation and rheological behavior. Examples of these studies included Pethrick et cd. [47,48], who applied a curome-ter to monitor the pot life and gel time of thermoplastic-modified epoxy systems. In 1999, Bormet and Pascault et al. [49] were the first to conduct a study of the relationship between rheological behavior and thermoplastic concentration in pol-yetherimide-modified epoxy-amine systems. By using an isothermal steady shear test with parallel plates at low deformation (1%), these authors showed that the rheological behavior at phase separation was greatly dependent on the initial concentration of thermoplastics. 

For a low-thermoplastic-concentration system with phase dispersion structure, the phase separation process was followed by a rapid decrease in viscosity, which was induced by the initially dissolved highly viscous thermoplastic component 

Thermosetting Blend Systems with Rubbers and Thermoplastics  

Whilst the composition with a final bicontinuous phase structure showed a more complex rheological behavior, the initial increase in viscosity at the start of the phase separation process was also due to the formation of a continuous thermoplastic-rich phase structure. However, a decrease of tj was observed shortly afterwards following destruction of the continuous thermoplastic-rich phase structure and the reappearance of an epoxy-rich matrix. 

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