Study of the particles’ structure dependent rheological behavior for polymer nanospheres based shear thickening fluid

• A novel kind of shear thickening fluid (STF) of polymer nanoparticles was developed.
• The particles’ structure dependent of the STF rheology was studied.
• A possible mechanism for the shear thickening (ST) behavior was proposed.
• The surface charges and hardness of the particles strongly affected the ST effects.

A novel kind of shear thickening fluid (STF) was developed via dispersing poly(styrene–acrylic acid) (PS–AA) nanospheres into ethylene glycol (EG). By varying the structure characteristics of the PS–AA particles, STFs with different rheological properties can be obtained. Firstly, the influence of the styrene/acrylic acid ratio on the PS–AA nanospheres was investigated. It was found that the higher ratio often led to the better shear thickening (ST) effects and under the optimum condition the maximum viscosity of the STF could reach to 152 Pa s, while the ST effects decreased under further increasing the monomer ratio. Then, the divinyl benzene (DVB) was introduced to increase the cross-link density of the PS–AA. In comparison with the non-cross-link PS–AA nanospheres, the poly(styrene–acrylic acid–divinyl benzene) (PS–AA–DVB) based STFs exhibited much higher ST effects and the maximum viscosity was up to 385 Pa s when the DVB was only increased to 0.3%. In combination of the rheological properties and the structure characterization, a possible mechanism for the ST behavior was proposed and the influence of the particles’ characteristics on the mechanical performance of the PS–AA based STF was carefully analyzed.

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