Flow-induced morphological instability in nanosilica-filled polyamide 6/polystyrene blends

Morphological stability of nanosilica-filled polyamide 6/polystyrene (PA6/PS) blends under flow was evaluated via online optical-shear technique and rheology methods. In the presence of nanosilica, the droplet size of as-prepared blends was refined at low hydrophilic nanosilica concentrations (1–3 vol.%). When a slow shear flow was imposed, the morphology of hydrophilic nanosilica-filled blends became unstable and displayed a promoted coalescence dynamics. These droplets broke up at high shear rates but the breakup dynamics was suppressed at high nanosilica concentrations. The flow-induced morphological discrepancies at different shear rates for the hydrophilic nanosilica-filled blends were discussed in terms of the significantly enhanced viscoelasticity of the droplets and the decreased interfacial tension of the blends induced by nanosilica. Correlation between the transient rheology and morphological evolution of these filled blends was also examined.