Enhancement of thermo‐rheological properties of smart materials based on SiO₂ and PPG modificated with expanded graphite

Abstract

The influence of expanded graphite (EG) on the thermal and rheological properties of shear thickening fluids (STF) based on silica powder with poly (propylene glycol) matrix was studied. Capturing the benefits of this non-Newtonian system in a fabricated material allows producing advance flexible protectors. However, in order to provide high protection potential in response to an external force, it is necessary to minimize negative effect of temperature on STF. The doping additives reduce the unfavorable effect of temperature increase on shear thickening flow during an impact through faster heat exchange and return to the initial state, characterized by the highest protective potential. EG in different volume fractions (0.10% -5.00%) as a partial substitution of STF and SiO 2 was added to studied systems and measured at temperatures in the range from 25.0 to 50.0°C. The dilatant effect of fluids increased by 580% for 5% volume fraction EG at 50.0°C.

Rheological and Technological Aspects in Designing the Properties of Shear Thickening Fluids

“…These modifiers can influence the viscosity in a significant way, even when used in small amounts [ 50 ]. The additives used include halloysite [ 51 ], aluminum oxide [ 52 ], cellulose nanofibers [ 53 ], silicon carbide [ 52 ], boron carbide [ 52 ], carbon nanotubes [ 18 ], graphene and graphene oxide [ 54 , 55 ], expanded graphite [ 56 , 57 ], or poly(propylene glycol) diacetate [ 58 ]. Often, the material property modifier can also be silica itself, e.g., in multiphase fluids [ 59 ].…”