Abstract
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.
Highlights
An increased demand for the quality of life and the increasing popularity of outdoor activities have led us to require outfits that offer functionalities other than comfort and beauty
The surface of Calcium chloride and the outermost layer of sodium alginate in W/O/W emulsion is cross-linked the capsule is rough, indicating resembles the pomelo peel, which contains a compact shell layer because the capsule is composed of a large number of closely arranged W/O/W complex emulsion covering the internal micro-pores filled with liquid [29]
Sodium alginate is cross-linked with calcium chloride for curing as gel shells that encapsulate shear thickening fluid (STF)
Summary
An increased demand for the quality of life and the increasing popularity of outdoor activities have led us to require outfits that offer functionalities other than comfort and beauty. Zhang et al successfully encapsulated STF and yielded double-layered capsules via interfacial polymerization, through which the cortex is polymerized from polyethyleneimine (PEI), diisocyanate prepolymer, and toluene [13] They used the two-step aggregation method, thereby increasing the operability of STF [14]. As a common and simple encapsulation method, orifice coagulation method has superior characteristics, such as simple device, easy operation, low cost, and uniform particle size. In this method, polymers from a nozzle are formed into capsules with sizes ranging from 500 μm to 1 mm by crosslinking and curing. The determined optimal capsule size could be used as a reference for conducting further studies
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