Effect of shear thickening gel on structure and properties of flexible polyurethane foam

Compression and low-velocity impact properties of shear thickening gel/polyurethane foam (STG/PUF), a soft protective material, have been reported. In order to have a deeper understanding of the relationship between the structure and properties of this material, we utilized Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and Proton nuclear magnetic resonance (¹H-NMR) to study and prove that STG and polyurethane (PU) did not produce new chemical bonds during the blending process, which belongs to physical blending. Because the molecular chains of STG and PU are intertwined, the composites are endowed with higher thermal stability, safety protection performance, and shape memory performance. For instance, Young’s modulus (E) of the STG/PUF was automatically increased by 57% when stimulated by external forces at different rates and the E_max over 200 kPa, demonstrating a pronounced shear thickening effect. Shape memory tests showed that the shape fixity ratio of STG/PUF gradually increases with the increase of STG content, and the shape recovery ratio remained at 100%. More importantly, the STG/PUF was flexible and comfortable, had excellent mechanical properties and a longer service life, and can be extended to various human protective equipment.