Understanding the cavitation and crazing behavior in the polymer nanocomposite by tuning shape and size of nanofiller

H Zhang and RB Ma and DD Luo and W Xu and YF Zhao and XY Zhao and YY Gao and LQ Zhang, POLYMER, 188, 122103 (2020).

DOI: 10.1016/j.polymer.2019.122103

It is very crucial to understand the fracture mechanism of the polymer nanocomposites (PNCs) on the molecular level. In this work, the effect of the shape and size of nanofillers on it has been investigated in details by adopting a coarse-grained molecular dynamics simulation. First, the fracture energy of PNCs is found to be much higher for rod fillers than for sheet fillers and sphere fillers. Then it is reduced with increasing the nanofiller size much faster for sphere fillers than for sheet fillers and rod fillers which results from their interface and network. To better understand it, the bond orientation degree is characterized which can reflect the elongation. By calculating the stress contribution of matrix chains and nanofillers, the stress borne by matrix chains gradually decreases with the increase of nanofiller size for sphere fillers and sheet fillers while it is nearly same for rod fillers. In addition, the stress borne by sphere filler is gradually reduced with the nanofiller size while it borne by rod fillers and sheet fillers rises. The former is closely related to the number of the interfacial beads which bear the high stress while the latter is attributed to the stress contribution by the bond/angle energy. Furthermore, the number of voids is quantified which first increases and then decreases with the strain which reflects the generation and coalescence of voids. Meanwhile, the voids prefer to nucleate in the matrix which is a weak region at the strong interfacial interaction. Last, the maximum number of voids gradually increases with the nanofiller size for sphere fillers and sheet fillers while it is nearly unchanged for rod fillers which is consistent with the matrix region. In summary, this work could provide a further understanding how the nanofiller shape affects the fracture properties of PNCs.

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