Arrested Coalescence of Droplets in PBD/PDMS Blends†

doi:10.7503/cjcu20130674

Abstract

Abstract:

We investigated the effect of silica nanoparticle loading, dispersed phase fraction and shear rate on the arrested coalescence in immiscible blends of polybutadiene/polydimethylsiloxane(PBD/PDMS) under simple shear flow by an online optical-shear system. It was found that the size and regularity of the non-spherical PBD droplets resulted from arrested coalescence were determined by SiO₂ nanoparticles loading, dispersed phase fraction and shear rate. At low SiO₂ nanoparticle loading or high dispersed phase fractions, the coalescence of PBD droplets induced at low shear rate can be arrested by the nanoparticles at the interface, leading to the formation of large and irregular droplets. Increasing SiO₂ nanoparticles loading, decreasing dispersed phase fraction or increasing shear rate can greatly decrease the size of the PBD droplets and improve their regularity. The results should be closely related to SiO₂ nanoparticles coverage at the interface of the PBD droplets.

Key words: Immiscible polymer blend, Arrested coalescence, Silica nanoparticle, Shear flow, Polybutadiene, Polydimethylsiloxane

CLC Number:

O631
O641

TrendMD:

ZOU Zhiming, LI Zhanwei, FU Cuiliu, SUN Zhaoyan, AN Lijia. Arrested Coalescence of Droplets in PBD/PDMS Blends^†[J]. Chem. J. Chinese Universities, 2014, 35(2): 421.

Figures/Tables 7

Fig.1 Optical microscopies of PBD/PDMS/SiO2(10∶90∶0.1) blends in simple shear flow at shear rate γ·=0.1 s-1 with different timet/min: (A) 0; (B) 1; (C) 10; (D) 60; (E) 360; (F) 720.

Fig.2 Morphologies of PBD/PDMS/SiO2(10∶90∶x) blends after shearing at γ·=0.1 s-1 for 720 min x(%): (A) 0.1; (B) 0.5; (C) 1.0.

Fig.3 Evolution of volume average radius(RV) and the average roundness(Circ) of the PBD droplets as a function of shearing time at 0.1 s-1 for SiO2 particles loading in a PBD/PDMS(10/90) blendMass fraction of SiO2 particles(%): □,■: 0.1; ○,●: 0.5;△,▲: 1.0.

Fig.4 Effect of dispersed phase concentration on morphology of PBD/PDMS blends at SiO2 particles loading of 0.1% after shearing at γ·=0.1 s-1 for 720 minMass ratio of PBD/PDMS: (A) 5∶95; (B) 10∶90; (C) 20∶80.

Fig.5 Effect of dispersed phase weight fraction on the evolution of RV and Circ of the PBD droplets as a function of shearing time at 0.1 s-1 for PBD/PDMS blends filled with 0.1%SiO2 particles loading Mass ratio of PBD/PHS: □,■ 5∶95; ○,● 10∶90;△,▲ 20∶80.

Fig.6 Morphology of PBD/PDMS/SiO2(10∶90∶0.1) blends after shearing for 720 min at different shear rate γ· γ·/s-1: (A) 0.1; (B) 0.5; (C) 1.0.

Fig.7 Evolution of RVand Circ of PBD droplets in PBD/PDMS/SiO2(10∶90∶0.1) blends as a function of shearing time at different shear rateShear rate/s-1: □,■ 0.1; ○,● 0.5; △,▲ 1.0.

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