Shear rheometry of polydimethylsiloxanes. Master curves and testing of Gleissle and Yamamoto relations

Abstract

This study concerns the shear rheometry of a series of nine silicone fluids, all linear or branched polydimethylsiloxanes (PDMS), with varying mass distributions.

The use of a rotative rheometer enabled characterization of these products in a dynamic regime for about five decades of pulsation ω. In addition, because of the use of rotative rheometers together with a capillary rheometer with controlled piston speed, the behavior of these products could be determined for about six orders of magnitude of shear rate $\dot \gamma$, notably for the permanent regime viscosity coefficient ν.

On the other hand, to obtain the variations of the first normal stress difference coefficient ψ₁, over a significant range of shear rate $\dot \gamma$, it was necessary to complete the experimental measurements by using empirical relations. Particularly, after having defined the application conditions, the Gleissle and Yamamoto relations were tested for these products.

Finally, all the results obtained in dynamic and in transitory regimes by using the rheometers and empirical relations mentioned above were combined in dimensionless form. Indeed, the existence of master curves for the linear and branched PDMS was demonstrated. Our study therefore enables the validity of the master curve method, initially established for a series of linear monodisperse polystyrenes, to be extended to the case of a family of linear or branched PDMS of wide mass distribution.