Rheological and technological aspects in designing the properties of shear thickening fluids

Abstract

This work focuses on shear thickening fluids (STFs) as ceramic–polymer composites with outstanding protective properties. The investigation aims to determine the influence of raw material parameters on the functional properties of STFs. The following analyses were used to characterize both the raw materials and the STFs: scanning electron microscopy, dynamic light scattering, matrix-assisted laser desorption/ionization time-of-flight, chemical sorption analysis, rheological analysis, and kinetic energy dissipation tests. It was confirmed that the morphology of the solid particles plays a key role in designing the rheological and protective properties of STFs. In the case of irregular silica, shear thickening properties can be obtained from a solid content of 12.5 vol.%. For spherical silica, the limit for achieving shear thickening behavior is 40 vol.%. The viscosity curve analysis allowed for the introduction of a new parameter defining the functional properties of STFs: the technological critical shear rate. The ability of STFs to dissipate kinetic energy was determined using a unique device that allows pure fluids to be tested without prior encapsulation. Because of this, it was possible to observe even slight differences in the protective properties between different STFs, which has not been possible so far. During tests with an energy of 50 J, the dissipation factor was over 96%.