Multifunctional Polyurethane Composite Foam with Outstanding Anti-impact Capacity for Soft Body Armors

Herein, a multifunctional polyurethane (PU) composite foam with a hierarchical structure is fabricated by dip-coating a carbon nanotube/shear-thickening gel (CNT/STG) and spray-coating nano-SiO₂/STG on PU foam. The prepared nano-SiO₂/CNT/STG@PU (SCS@PU) composite foam is lightweight, highly compressive, electrically conductive, superhydrophobic, and impact-energy absorptive. As a result, it possesses an excellent sensing ability to compression with a stable response up to 80% strain, an outstanding linearity of R² > 0.99, and a wide response frequency of 0.01 to 1 Hz; it can also be used for effectively detecting impact force and sensing various human motions. Moreover, the superhydrophobicity with a water contact angle up to 154° of SCS@PU composite foam endows it with an excellent resistance to hazardous liquids (strong acid and alkali) to ensure its service reliability under harsh circumstances. In particular, the SCS@PU exhibits an outstanding anti-impact capability with an impact force attenuation rate of SCS@PU as high as 81%. Finally, its applications as soft body armors are demonstrated in protecting a wearer wearing a helmet with the SCS@PU as liner and using the SCS@PU as a smart kneecap against impact. On consideration of its excellent strain-sensing ability, superhydrophobicity, and outstanding anti-impact capability, the multifunctional SCS@PU composite foam developed is promising for personal safety protection.