Effect of Interfacial Bonding on Interphase Properties in SiO₂/Epoxy Nanocomposite: A Molecular Dynamics Simulation Study

Abstract

Atomistic molecular dynamics simulations have been performed to explore the effect of interfacial bonding on the interphase properties of a nanocomposite system that consists of a silica nanoparticle and the highly cross-linked epoxy matrix. For the structural properties, results show that interfacial covalent bonding can broaden the interphase region by increasing the radial effect range of fluctuated mass density and oriented chains, as well as strengthen the interphase region by improving the thermal stability of interfacial van der Waals excluded volume and reducing the proportion of cis conformers of epoxy segments. The improved thermal stability of the interphase region in the covalently bonded model results in an increase of ∼21 K in the glass transition temperature (Tg) compared to that of the pure epoxy. It is also found that interfacial covalent bonding mainly restricts the volume thermal expansion of the model at temperatures near or larger than Tg. Furthermore, investigations from mean-square displacement and fraction of immobile atoms point out that interfacial covalent and noncovalent bonding induces lower and higher mobility of interphase atoms than that of the pure epoxy, respectively. The obtained critical interfacial bonding ratio when the interphase and matrix atoms have the same mobility is 5.8%. These results demonstrate that the glass transitions of the interphase and matrix will be asynchronous when the interfacial bonding ratio is not 5.8%. Specifically, the interphase region will trigger the glass transition of the matrix when the ratio is larger than 5.8%, whereas it restrains the glass transition of the matrix when the ratio is smaller than 5.8%.

Effect of Aminosilane Coupling Agents with Different Chain Lengths on Thermo-Mechanical Properties of Cross-Linked Epoxy Resin

“…The results indicate that the aminosilane coupling agents could improve the thermal properties of the cross-linked epoxy resin. In some examples within the literature [9,11,32,33,34], the glass transition temperature shifted T g from 400 K to 483 K. Different epoxy resin monomers, curing agents, and experimental conditions make the T g different to some extent, which indicates that the simulation in this paper has certain reliability.…”

“…The pure epoxy resin model, the EP/SiO 2 composite model (the surface of SiO 2 without any modifier), and surface of the silica respectively grafted with epoxy resin doped with 3-aminopropyltriethoxysilane (A1100), N -(2-aminoethyl)-3-aminopropyltrimethoxysilane (A1120), and 3-[2-(2-aminoethylamino)ethylamino (A1130) were built, which were represented as pure, SiO 2 , A1100, A1120, and A1130. In this paper, COMPASS [11,14,15,16,17,18] was selected as the force field for calculations in all dynamic simulations; Nose [18] and Berendsen [19] were used for temperature control and pressure control, respectively. Figure 1 shows the SiO 2 composites and the pure epoxy resin model.…”

“…Chang et al [10] experimentally grafted amino on nano silica and studied the effect of modified silica on the corrosion resistance of epoxy resin composites. Wang et al [11] studied the effects of doped nano silica surface-grafted KH550 on the interfacial properties of epoxy resin. Li et al [2] used a silane coupling agent as a bridging agent, which grafted bisphenol-A type epoxy resin and nanoparticles to improve the mechanical properties of the composites, while reducing the real and imaginary parts of the complex dielectric constant of the composite.…”

Consistent discretization of higher-order interface models for thin layers and elastic material surfaces, enabled by isogeometric cut-cell methods

“…On the one hand, the direct numerical resolution of thin layers with continuum-based standard finite element or boundary element methods requires prohibitively fine mesh sizes [8]. On the other hand, molecular dynamics type approaches are often prohibitively expensive for sample sizes and at scales of engineering interest [9,10].…”

Thermodynamic simulations of SrTiO3/epoxy nanocomposites with different mass fractions

“…The results showed that the chemical bond in the interface region can increase the glass transition temperature of the epoxy resin by 21 K when the graft ratio exceeds 5.8%, which enhances the thermal conductivity of the composite model. In the meanwhile, the interfacial chemical bond can reduce the mobility of epoxy resin molecular chains [23]. Wang Y simulated the interfacial thermal resistance and thermal conductivity of SrTiO 3 particles, showing that the size of the nanoparticles is closely related to the thermal conductivity [24].…”