No abstract

In this paper, the shear-thickening fluids(STFs) are prepared by 0.5 µm and 12 nm silica particles. The STFs rheological properties and the performance of stab resistance are studied. SiO2 particles with two sizes (12 nm and 0.5 µm) are mixed at different weight ratios to form shear thickening fluids and its rheological behaviors are tested. Next, the quasi-static spike and knife stab resistances, dynamic impact strength, and yarn pull-out of shear thickening fluid-impregnated Kevlar fabrics are tested. The investigation showed that the micro- and nano-sized particles of silica are present in the compound shear thickening fluid, and the rheological behavior was positively improved. Regardless of whether shear thickening fluid is composed of mono-sized or binary particle-sized SiO2 particles, the presence of shear thickening fluids can significantly strengthen Kevlar fabrics in terms of the quasi-static spike and knife stab resistances, dynamic impact strength, and promote the friction force of inter-yarn. In particular, shear thickening fluid-impregnated Kevlar fabrics have better performances when being composed of 12 nm and 0.5 µm SiO2 particles at ratios of 2:1, 1:1, and 1:2 than when being made of only micro-sized or nano-sized particles.

No 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.

In this study, a double-walled and pomelo-like hierarchical shear thickening fluid (STF) is successfully encapsulated using the simple and environment-friendly calcium alginate encapsulation technique by instilling STF into sodium alginate (SA) and crosslinking by calcium chloride solution. The encapsulated STF has a pomelo-like structure with a shell thickness of 2.9 μm and core pores with a size of 21.43 μm. The effect of the size of STF capsules (2.10, 1.89, 1.86, 1.83, 1.73, and 1.63 mm) is explored in terms of thermal stability, swelling capacity, mechanical property, and release performance. The buffering performance of different sizes of STF-containing capsules is also investigated. The pomelo-like STF capsules can withstand a processing temperature of 250 °C. With a decrease in particle size, the compression strain energy slowly increases first and then rapidly enhances. The kinetic release of pomelo-like STF capsules conforms to Fickian diffusion. STF-containing capsules with a diameter of 1.83 mm present the greatest thermal stability, the highest STF amount, the maximum swelling coefficient, and the fastest kinetic diffusion. STF-containing capsules also have an improved buffering performance in PU foam. This capsule has the best comprehensive performance and can adapt to diversified applications, such as personnel armor and other protective sports equipment.