Chemoviscosity shear effects

Recent work has included tests that examine the effects of shear rate and cure simultaneously (which will also be discussed below). The models derived from these tests are recombined to provide an overall chemoviscosity model to be used in processing applications. The effect of pressure on chemoviscosity has not been studied extensively however, system pressure may be relevant to high-pressure injection-moulding and transfer-moulding processes. 

The shear-rate effect on the viscosity of thermosetting resins, r]Jff), is also essential to the determination of the chemoviscosity, r]. The exact relationship will depend on the type of... 

The work of several authors (Peters et al, 1993, Halley et al, 1994) has demonstrated the use of non-isothermal dynamic sweep tests to examine the combined effects of shear rate and curing on the chemoviscosity of a highly filled epoxy resin simultaneously. These tests use a selected temperature ramp with repeated dynamic rate sweeps to investigate the effects on the chemoviscosity. The advantage of these tests is that the effects of shear rate and cure are not separated, which is similar to processing conditions. 

Simple chemoviscosity models have been used to examine the effects of shear rate on the chemoviscosity = T) as shown in Table 4.3. For example, Sundstrom and Burkett (1981) and Hartley and Williams (1981) found that polyesters and polyurethanes exhibit essentially Newtonian behaviour, whereas epoxies and phenolics show marked shear thinning. The power-law model is the most extensively used shear-rate model for thermosets and has been used for unfilled (Ryan and Kamal, 1976, Kascaval et al, 1993,... 

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