Uncovering the rupture mechanism of carbon nanotube filled cis-1,4-polybutadiene via molecular dynamics simulation

In this work, by employing molecular dynamics simulations in a united atomistic resolution, we explored the rupture mechanism of carbon nanotube (CNT) filled cis-1,4-polybutadiene (PB) nanocomposites. We observed that the rupture resistance capability increases with the interfacial interaction between PB and CNTs, as well as the loading of CNTs, attributed to the enhanced chain orientation along the deformed direction to sustain the external force, particularly those near voids. The number of voids is quantified as a function of the strain, exhibiting a non-monotonic behavior because of the coalescence of small voids into larger ones at high strain. However, the number of voids is greatly reduced by stronger PB–CNT interaction and higher loading of CNTs. During the rupture process, the maximum van der Waals energy change reflects the maximum conformational transition rate and the largest number of voids. Meanwhile, the strain at the maximum orientation degree of bonds is roughly consistent with that at the maximum square radius of gyration of chains. After the failure, the stress gradually decreases with the strain, accompanied by the contraction of the highly orientated polymer bundles. In particular, with weak interfacial interaction, the nucleation of voids occurs in the interface, and in the polymer matrix in the strong case. In general, this work could provide some fundamental understanding of the voids occurring in polymer nanocomposites (PNCs), with the aim to design and fabricate high performance PNCs.