Molecular Dynamics Insight into the Effect of Chain Extension and Nonbond Interaction in Nanoparticle-Enhanced Plastic and Elastomer Double-Phase Recyclable Polymer Materials

Polymer nanocomposites (PNCs) demonstrate excellent mechanical properties through the addition of fillers to the polymer, making them versatile for various applications. However, the current challenge lies in the recycling of these PNCs. To investigate the performance changes in PNCs during the recycling process, a two-phase polymer was designed by using coarse-grained molecular dynamics simulations. Nanoparticles (NPs) with linear and ring structures were introduced to construct PNCs, and chain extenders (CEs) were added to realize chain extension reactions. The changes in the performance of PNCs with different proportions during the recycling process were explored by varying the amounts of CEs. Our results demonstrate that the variations in mechanical properties, as evidenced by the stress–strain curves, strain hardening trends, and rates of performance loss, are consistent across all PNCs, irrespective of the CE concentration. Analysis of the dynamic changes in NPs and matrix chains during the deformation process confirms that the influence of NPs is orientation-dependent. It can be inferred that the amount of CEs in PNCs has a completely different effect on the performance of those recycled many times. The incorporation of 75 CEs results in a matrix of long-chain polymers with varying molecular weights, which significantly enhances the mechanical properties. Overall, this study offers essential theoretical guidance and practical strategies for selecting and determining the optimal content of additives for the production and recycling of PNCs.