Role of surface chemistry of fibres additives on rheological behavior of ceramic particle based Shear Thickening Fluids

Influence of surface chemistry and size (fineness) of fibres as additives on the rheological behavior of ceramic particle (silica) based Shear Thickening Fluid (STF) has been investigated in this research work. Two different types of fibres, Kevlar microfibres (KMF) and chemically modified cellulose nanofibres (M-CNF) were used for tuning the rheological characteristics of STFs. The extraction of both the fibres, was carried out using supermasscollider. The CNFs were then chemically modified with vinyl silane to impart hydrophobic character to the nano-fibres. The characterization was done by TEM-EDX and contact angle analyzer. Ultrasonication was used to obtain the fibres reinforced STFs. In both STFs, reduction in peak viscosity in comparison to virgin STFs was observed with increasing concentration of fibres in STFs. Interaction between additive fibres, silica and media (PEG) was assessed by dynamic state rheological analysis. The crossover point between storage (G ') and loss modulus (G '') for both cases (KMF & M-CNF) shifted towards lower frequency as concentration of fibres additives in STFs increased. It is postulated that presence of fibres with hydrophobic characters reduces the interaction between hydrophilic particles and fibres leading to decrease in peak viscosity and increase in critical shear rate.