Polyimide/Silica Nanocomposites with Enhanced Tensile Strength: Size Effects and Covalently Bonded Interface

Abstract

In this work, the tensile strength of polyimide/silica composites with the covalently bonded interface (bonded PI/SiO 2 ) is investigated by molecular dynamic simulation. It is found that the nanofiller with smaller size can bring out a larger number of hydrogen bonds and interfacial non-bond energy in the composites, resulting in higher tensile strength. As the immobilization of the PI chains in the vicinity of SiO 2 , the covalently bonded interface is found to offer a greater reinforcing effect than the unbonded interface that is confirmed by the self-diffusion coefficient. The tensile strength of 9 wt.% bonded PI/SiO 2 composites is 11.34% higher than that of the unbounded composites. The tensile strength of PI/SiO 2 composites is enhanced with the increase of SiO 2 concentration up to critical mass percent (X c ), beyond which it will be decreased. To quantitatively predict X c of PI/SiO 2 composites, an empirical equation based on the non-bond energy of the composites is proposed. The empirical equation showed that the X c of PI/SiO 2 composites ranged from 8.03 to 10.36 wt.%, which is consistent with experimental values. These results provided the understanding of size-dependent covalently bonded interface structure, which would be beneficial to the design of nanocomposites with excellent mechanical performances.

Constructing high‐polarization silica for polyimide‐based nanocomposites with enhanced dielectric permittivity and mechanical performances: Molecular dynamics simulations

“…The optimization methods of PI/SiO 2 composite models had been introduced in detail in a previous study. 35 The optimized PI/SiO 2 composite model was shown in Figure 1c. To minimize the random error in the simulation, all the simulation results were repeated three times at least.…”

“…Many studies have demonstrated that organic molecules can improve the interfacial strength and the mechanical properties of the composites. [35][36][37] Compared to polymer modifications with the complex preparation process, flexible and controllable silane coupling agents are favored to reinforce the load transfer efficiency in the composites. However, few studies have attempted to investigate the silane coupling agents that can elevate the ε r and mechanical properties of the composites simultaneously.…”

Atomic Insight into Multilevel Microstructure Evolution and Energy Variation Mechanisms of Polyimide under Shock Compression

“…Their calculations demonstrated that reduced local mobility above the glass transition point increased the yield stress (σ y ) and decreased the Poisson’s ratio (μ) in a glassy state. Additionally, researchers also extensively explored the mechanical properties of PI materials enhanced by nanoparticles, graphene, and carbon nanotube (CNT) , through MD methods.…”