Influence of Hydrogen Bonding Structures on the Mechanical Properties of Polyurea Elastomers Under Quasi‐Static and Dynamic Loadings

ABSTRACT

Polyurea (PUA) elastomers have been widely applied in impact protection fields owing to their excellent mechanical properties. However, the influences of hydrogen bonding structures on the mechanical properties of PUA elastomers under quasi‐static and dynamic loadings remain unclear. Herein, two small molecular amines, hexamethylene diamine and oxalyl dihydrazide, with identical molecular weight and different molecular structures were used as chain extenders to obtain PUA elastomers with quadruple and sextuple hydrogen bonding structures, respectively. Hydrogen bonding and micro phase separated structures of PUA were characterized by FTIR and SAXS. Quasi‐static mechanical performances, including tensile strength, elastic modulus, and energy dissipation capability, are significantly enhanced with increasing content and hydrogen bonding multiplicity of hard segments. Under dynamic loadings, the storage/loss moduli increase markedly with increasing content and hydrogen bonding multiplicity of hard segments in a wide temperature range. In the 0–7000 s ⁻¹ strain rate range, PUA with sextuple hydrogen bonding structure shows enhanced compressive stress and more pronounced strain rate sensitivity. The glass transition temperature/frequency is almost unaffected by the content and hydrogen bonding multiplicity of hard segments. This work provides valuable insights for molecular design of PUA elastomers with tailored impact protection performance.