Anti-puncture, frigostable, and flexible hydrogel-based composites for soft armor

Cold adaptation is essential to the protective effect of soft armor and other protective materials because of the potential for prolonged exposure to freezing conditions in service, while the properties of flexible matrices are always affected by low temperatures. To integrate the good protection efficiency and excellent anti-freezing properties, polyvinyl alcohol (PVA), sodium alginate (SA), and glycerol (Gly) were selected to prepare a frigostable hydrogel in this study. Afterward, the hydrogel was laminated with aramid fabric to obtain a flexible anti-puncture composite that can be used at low temperatures. At −30 °C, the breaking strength and elongation of PVA/SA/Gly hydrogel reached 1.32 MPa and 330%, which was basically the same as at room temperature, indicating its excellent cold adaptation. Meanwhile, the maximum puncture resistance force and energy dissipation of the aramid/hydrogel composite at −30 °C were 56.88 N and 263.07 mJ, respectively, 289% and 184% higher than that of neat fabric, while the weight gain rate of the composite was only 40%. At room and low temperatures, the flexibility of the composite was only 5% and 8% lower than that of the neat fabric, respectively, and a helix shape of 360° could be formed and maintained under a small torsional force even at −30 °C.