Coarse-grained molecular simulation of the effects of carbon nanotube dispersion on the mechanics of semicrystalline polymer nanocomposites

Abstract

With the incorporation of carbon nanotubes (CNTs), CNT/polypropylene (PP) nanocomposites are found to possess enhanced mechanical properties, but the reinforcing effect is reduced at large added CNT weight percentages due to CNT aggregation. Optimizing the properties of a nanocomposite requires a fundamental understanding of the effects of CNT dispersion on the nanocomposite. In this work, coarse-grained molecular models of CNT/PP nanocomposites are constructed, which consist of randomly dispersed or aggregated CNT bundles. Our simulation results reveal that with randomly dispersed CNT bundles, the nanocomposite shows properties that continuously improve with increasing CNT contents due to the effective CNT/PP interface and the reinforcing effect of CNTs. By comparison, the nanocomposite with aggregated CNT clusters exhibits a decline in yield strength at CNT contents over 3 wt%, which results from a reduced CNT load-carrying capacity due to the formation of structural voids in the interfacial region. This study achieves an in situ observation of the structural void evolution of loaded nanocomposites, provides valuable insights into the effects of CNT dispersion on the mechanics of CNT/PP nanocomposites, and paves the way for optimizing the design of nanocomposites with superior mechanical properties by designing the CNT dispersion in the structure.

A coarse-grained model for capturing the helical behavior of isotactic polypropylene

“…Recent studies use even coarser schemes, choosing a Kuhn monomer to represent a bead. 30,31 The challenge in polypropylene coarse-graining is connected to its structure. Specifically, polypropylene is a branched vinyl polymer which exhibits a tendency to form helices.…”

Hybrids of glass fibers coated with carbon nanotubes and nickel for high‐performance electromagnetic wave absorption composites

“…However, due to the strong Van der Waals forces, CNTs are easy to aggregate and difficult to be uniformly dispersed in the matrix 26 . In our previous work, we have reported a hybrid where CNTs grow directly on the surface of fibers, which has been a promising method to improve the CNT dispersion in the matrix 27,28 .…”

“…In the conductive fillers, CNTs have been widely applied in the EM wave absorbing materials because of their high conductivity and compatibility with polymer matrix 24,25 . However, due to the strong Van der Waals forces, CNTs are easy to aggregate and difficult to be uniformly dispersed in the matrix 26 . In our previous work, we have reported a hybrid where CNTs grow directly on the surface of fibers, which has been a promising method to improve the CNT dispersion in the matrix 27,28 …”

Tensile Performance of Polymer Nanocomposites with Randomly Dispersed Carbon Nanothreads

“…The enhancements reported thus far are much lower than or inconsistent with the theoretical predictions. For example, it is observed from experiments that CNTs/polypropylene composites exhibit the highest mechanical properties at 0.5–1.0 wt % CNT, while the atomistic simulation predicted that Young’s modulus gradually increases with CNTs’ content up to 9.0 wt % …”

“…Previous works suggest that a uniform dispersion is the key to minimize the presence of stress concentration and achieve efficient load transfer between the nanofiller and polymer matrix. Researchers found that a poor dispersion results in severe aggregation at a relatively large CNT content (e.g., 5.0 wt % of CNTs in polypropylene , ), which leads to a lower yield strength, hardness, and indentation modulus. Therefore, continuing efforts have been devoted to improve the dispersion of CNTs, such as the usage of physical treatment, electrostatic treatment, , and surfactants .…”