Interface Characterization of Epoxy Resin Nanocomposites: A Molecular Dynamics Approach

Abstract

In polymer nanocomposites, the interface region between the matrix and the fillers has been identified as a key interaction region that strongly determines the properties of the final material. Determining its structure is crucial from several points of view, from modeling (i.e., properties prediction) to materials science (i.e., understanding properties/structure relationships). In the presented paper, a method for characterizing the interface region of polymer nanocomposites is described using molecular dynamics (MD) simulations. In particular, the structure of the polymer within the interface region together with its dimension in terms of thickness were analyzed through density profiles. Epoxy resin nanocomposites based on diglycidyl ether of bisphenol A (DGEBA) were studied using this approach, and the interface region with triple walled carbon nanotubes (TWCNT) and carbon fibers (CF) was characterized. The effect of carbon nanotube diameter, type of hardener, and effect of epoxy resin cross-linking degree on interface thickness were analyzed using MD models. From this analysis no general rule on the effect of these parameters on the interface thickness could be established, since in some cases overlapping effects between the analyzed parameters were observed, and each specific case needs to be analyzed independently in detail. Results show that the diameter has an impact on interface thickness, but this effect is affected by the cross-linking degree of the epoxy resin. The type of hardener also has a certain influence on the interface thickness.

Interface Structure and Dynamics in Polymer‐Nanoparticle Hybrids: A Review on Molecular Mechanisms Underlying the Improved Interfaces

“…Since the filler does not influence the bulk polymer region, the density fluctuations persist stable, and the related standard deviation (SD) takes a particular specific value. Considering this effect, Ezquerro et al., 2019, [122] presented a method for characterizing the interface region in triple‐walled carbon nanotubes (TWCNT) filled epoxy resin PNCs via density profiles in a more mathematical way, by calculating the accumulated standard deviation (ASD) profiles as given below. …”

Heat Transfer at the Interface of Graphene Nanoribbons with Different Relative Orientations and Gaps

“…Similarly to the typical empirical expressions adopted for heat transfer, only basic formula building-blocks (i.e., constant, multiplication, division, power) have been considered for the Eureqa fitting. As a result, the simulation results in Table A1 (configurations N. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] have been found to be best fitted (R 2 = 0.99, see Figure 4b) by the following expression:…”

“…Carbon fillers such as carbon nanotubes and graphene nanoribbons are often suggested as possible additives in composite materials. In fact, these materials show a remarkable combination of superior thermal [1][2][3][4], electrical [5][6][7], lubrication [8,9] and mechanical [10][11][12] properties, which have the potential to significantly enhance the performance of base materials. In particular, Polymer Nanocomposites (PNCs) with carbon nanofillers are currently employed in a broad variety of industries, such as the energy [13], aerospace [14], biomedical [15], electronics [16,17] and automotive ones [18,19].…”

Effects of Graphene Oxidation on Interaction Energy and Interfacial Thermal Conductivity of Polymer Nanocomposite: A Molecular Dynamics Approach

“…Then, the models were time integrated in the isobaric–isotherm ensemble (NPT, with the Nosé–Hoover thermobarostat) at 300 K and 1 atm, allowing all atoms to freely move, until reaching the plateau in density (which typically required between 0.5 and 1 ns). In the case of the epoxy resin, the cross-linking procedure, based on methods described in literature [ 14 , 20 ] and performed through consecutive steps of molecular dynamics simulations, was subsequently applied to obtain the desired cross-linking degree of 70%. At the abovementioned conditions used for the systems stabilizations, the PLA and EPO are in the glassy state, while the polypropylene is in the melting state, as reported in previous studies available in the literature [ 22 , 23 , 24 ].…”

“…Similarly, Bigdeli and Fasano [ 12 ] and Mohammad Nejad et al [ 13 ] demonstrated, through reverse nonequilibrium molecular dynamics (RNEMD) simulations, that both geometry properties and the thermal boundary resistance between fillers affect significantly the overall thermal properties. In terms of the interactions between the matrices and the fillers, Sáenz et al [ 14 ] evaluated the interface thickness of composites based on epoxy resin and triple wall carbon nanotubes (TWCNT), by analyzing the density profile. Sun et al [ 15 ] calculated the interaction energy between epoxy resin and GO depending on the content of hydroxyl groups, identifying the range in which the interfacial energy seemed to decrease more sensibly by increasing the number of hydroxyls.…”