Abstract
The orifice coagulation bath method is proposed to encapsulate shear thickening fluid (STF) to form STF capsules, in an attempt to improve the combination of STF and the matrix as well as strengthen the flexibility and stability of the STF composites. By varying the calcium chloride concentration (10, 20 mg/mL), sodium alginate concentration (5, 7, 10 mg/mL) and the surfactant dosage (10%, 20%, 30%), optimal preparation conditions were studied, considering the capsule strength and encapsulation rate. The capsules were also characterized using a scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and a thermogravimetric analyzer (TGA). The results show that the optimal solution for the preparation of the capsules is composed of 30% surfactant, 10 mg/mL mass concentration of CaCl2, and 10 mg/mL mass concentration of sodium alginate. The rough surface and porous interior was observed by SEM. The average diameter of the capsules was 1.93 mm. The TGA curves indicate an improvement on the capsule thermal stability. This study thus provides a promising STF capsule preparation method.
Highlights
Shear thickening fluid (STF) is a non-Newtonian fluid with a viscosity that increases with the shear rate, especially at a critical shear rate, which triggers an upsurge of viscosity [1,2,3]
Thermogravimetric analysis (TGA) is effective to characterize the thermal stability of the emulsion and shear thickening fluid (STF)
Thermogravimetric analysis (TGA) is effective to characterize the thermal stability of the capsule as Polyethylene glycol (PEG) and water
Summary
Shear thickening fluid (STF) is a non-Newtonian fluid with a viscosity that increases with the shear rate, especially at a critical shear rate, which triggers an upsurge of viscosity [1,2,3]. STF encapsulation means to encapsulate STF in the spherical membrane, after which the membrane solidifies to a shell and forms a solid capsule This solidification of the membrane can be attained via chemical, physical or physicochemical methods. Compared to the quasi-static compression, STF capsules exhibited an absorption nominal strain which was 154 times greater, providing an efficient shear thickening effect against dynamic impact [17]. With respect to these advantages, the orifice coagulation bath method is proposed to produce the gel beads with post-encapsulated curing. The exterior calcium alginate shell can absorb the impact energy, strengthening STF capsules. This study proposes a new method to encapsulate STF and will serve as a valuable reference
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