Rheological Study of Silica Filled PDMS

The rheological behaviour of silica nano-particles in a series of monodispersed Polydimethylsiloxane (PDMS) samples is studied. It was found that even 1%wt silica had a significant effect on the mobility of the polymer, increasing it by ten fold. At higher weight percent of silica, a further increase in viscosity is observed, however this is not so marked as expected. This finding might be due to the effects of distance between particles and molecular weight.

Unlike pure, low molecular weight PDMS, a Newtonian region is not observed. At increasing shear rate, the viscosities of the particle filled polymers decrease and they begin to approach the viscosity of pure PDMS. This behaviour suggests that the majority of particle-polymer interactions are broken and a further decrease in viscosity should be observed at the point where the onset of shear thinning occurs in pure PDMS.