A coarse‐grained molecular dynamics study on the mechanical behavior of carbon nanotubes reinforced vulcanized natural rubber composites

Abstract

In the present study, coarse‐grained (CG) molecular models of carbon nanotubes (CNTs) strengthened vulcanized natural rubber (VNR) composites are constructed to systematically investigate the effects of length, inter‐tube cross‐linking, and polymer‐grafting of CNTs on the stress–strain behavior of VNR composites under uniaxial tension. The interfacial CG force field between CNTs and VNR is derived via the energy matching approach. The results demonstrate that increasing the length of CNTs is able to effectively enhance the mechanical performance of VNR composites, and the reinforcing efficiency increases gradually and tends to stabilize with increasing CNT length. Moreover, the cross‐linking and polymer‐grafting of CNTs are also effective approaches to significantly enhance the mechanical performance of VNR composites. The enhancement mechanism of CNTs is interpreted from the perspective of CNT networks, VNR networks, CNT‐VNR interface networks, and the interfacial load‐transfer behavior. Specifically, the dispersion of CNTs, the orientation of CNTs and VNR molecular chains, and the wrapping and interlocking behaviors between CNTs and the VNR matrix reveal a detailed structure‐mechanics relationship of CNTs‐reinforced VNR composites at the molecular level. These findings present theoretical instruction for the structural design of high‐performance rubber composites.Highlights A coarse‐grained model of carbon nanotube‐natural rubber composites is built. The composite network structures are quantitatively characterized. The length, cross‐linking, and grafting effects of carbon nanotubes are studied. The reinforcement mechanisms of carbon nanotubes are revealed.

Analysis of static and dynamic mechanical properties of carbon black/carbon nanotubes hybrid filled natural rubber nanocomposites using coarse‐grained molecular dynamics

“…From Figure 5B, it can be clearly observed that, the of NR molecular chains in the five CG models gradually increases with increasing true strain, which is mainly due to the strain‐induced orientation and crystallization of NR molecular chains. Moreover, the introduction of NPs promotes the orientation of NR molecular chains along the deformation direction by providing a strong interfacial adsorption, and the higher the CNT loading in hybrid NPs, the better the promoting effect, which can be attributed to the CNT‐induced orientation and crystallization behavior 22 . However, as the CNT loading increases, the rate of increase of the bond orientation parameter gradually decreases, which can be attributed to the agglomeration of CNTs. where is the angle between the bond and the deformation direction.…”

“…(iii) The CG force fields between the NR and NPs are constructed using hybrid EM and IBI methods. The CG force field between the NR and CNTs is developed using the EM method, and the detailed derivation process and CG force field parameters between the NR and CNTs can be found in our previous work 22 . The CG force field between the NR and CB is developed using the IBI method.…”

“…The CG force field between the NR and CNTs is developed using the EM method, and the detailed derivation process and CG force field parameters between the NR and CNTs can be found in our previous work. 22 The CG force field between the NR and CB is developed using the IBI method. Figure 1E shows the CG potential between the NR and CB obtained by the IBI method and its corresponding fitting curve of the shifted LJ potential, as well as the RDFs between CB and NR in the AA and CG models.…”

“…Moreover, the introduction of NPs promotes the orientation of NR molecular chains along the deformation direction by providing a strong interfacial adsorption, and the higher the CNT loading in hybrid NPs, the better the promoting effect, which can be attributed to the CNT-induced orientation and crystallization behavior. 22 However, as the CNT loading increases, the rate of increase of the bond orientation parameter gradually decreases, which can be attributed to the agglomeration of CNTs.…”

“…Yuan et al 16,17 constructed the CG force fields for the CB-and silica-filled NR nanocomposites using hybrid iterative Boltzmann inversion (IBI) [18][19][20] and effective force coarsegraining (EFCG) 21 methods, and then investigated the tensile behavior of silica-filled NR nanocomposites and the viscoelastic behavior of CB/silica hybrid NPs filled NR nanocomposites, respectively. Cui et al 22 employed the energy matching (EM) method to derive the CG interactions between CNTs and the NR matrix, and systematically studied the effects of length, inter-tube crosslinking, and polymer-grafting of CNTs on the tensile properties of NR nanocomposites. Zhou et al 23 investigated the uniaxial tensile and viscoelastic behaviors of graphene-filled NR nanocomposites using CGMD simulations.…”