Mesoscale structure-based investigation of polyurea dynamic modulus and shock-wave dissipation
KL Yao and ZL Liu and T Li and BH Guo and Z Zhuang, POLYMER, 202, 122741 (2020).
Polyurea is a block copolymer with excellent shock absorption. It has a unique phase separation structure, yet there are few reports on how the mesoscale structure affects the dynamic mechanical properties. In this paper, the effect of two-phase structure on the dynamic modulus and shock-wave dissipation of polyurea is investigated by coarse-grained molecular dynamics. Shear relaxation modulus is calculated by the Green- Kubo method. Pulse load is applied by non-equilibrium molecular dynamics. The two-phase structure improves the dynamic modulus by restricting the segment movement. Shock-wave energy is dissipated by heat dissipation, viscous retardation, and plastic dissipation. The two- phase structure must obey deformation coordination, which results in more strain energy and internal friction. Hydrogen bond dissociation and structure destruction occur during the impact. Furthermore, the simulations results are verified by AFM, X-ray diffraction, and DMA experiments.
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