Elucidating and tuning the strain-induced non-linear behavior of polymer nanocomposites: a detailed molecular dynamics simulation study

Abstract

By setting up a coarse-grained model of polymer nanocomposites, we monitored the change in the elastic modulus as a function of the strain, derived from the stress-strain behavior by determining uniaxial tension and simple shear of two typical spatial distribution states (aggregation and dispersion) of nanoparticles (NPs). In both these cases, we observed that the elastic modulus decreases non-linearly with the increase of strain and reaches a low plateau at larger strains. This phenomenon is similar to the so-called "Payne effect" for elastomer nanocomposites. Particularly, the modulus of the aggregation case is more sensitive to the imposed strain. By examining the structural parameters, such as the number of neighboring NPs, coordination number of NPs, root-mean-squared average force exerted on the NPs, local strain, chain conformations (bridge, dangle, loop, interface bead and connection bead), and the total interaction energy of NP-polymer and NP-NP, we inferred that the underlying mechanism of the aggregation case is the disintegration of the NP network or clusters formed through direct contact; however, for the dispersion case, the non-linear behavior is attributed to the destruction of the NP network or clusters formed through the bridging of adsorbed polymer segments among the NPs. The former physical network is influenced by NP-NP interaction and NP volume fraction, while the latter is influenced by NP-polymer interaction and NP volume fraction. Lastly, we found that for the dispersion case, further increasing the inter-particle distance or grafting NPs with polymer chains can effectively reduce the non-linear behavior due to the decrease of the physical network density. In general, this simulation work, for the first time, establishes the correlation between the micro-structural evolution and the strain-induced non-linear behavior of polymer nanocomposites, and sheds some light on how to reduce the "Payne effect".

Simulational insights into the mechanical response of prestretched double network filled elastomers

“…[48] A more detailed description of the simulation protocol can be found in our previous publications. [49][50] 3. Results and discussion…”

Interfacial interaction modes construction of various functional SSBR–silica towards high filler dispersion and excellent composites performances

“…36,37 As the interfacial interaction modes between silica and F-SSBRs followed the order single hydrogen bonds to dual hydrogen/covalent bonds to single covalent bonds, the compounds were ordered as follows with respect to the bound rubber contents: silica/SSBR-g-MPL70 < silica/SSBR-g-MUA70 < silica/SSBR-g-MPTES70, as listed in Table 1. The results indicated that the ller-rubber networks, which were formed through rubber chain bridges anchored onto adjacent llers, [38][39][40] increased gradually with the improving interfacial interactions. Moreover, the bound rubber contents of the silica/SSBR-g-MPTES compounds increased with increasing MPTES contents.…”

Hybrid of bamboo charcoal and silica by tetraethoxysilane hydrolysis over acid catalyst reinforced styrene‐butadiene rubber

“…There are usually two kinds of filler networks in a filler‐filled rubber. One is formed by filler‐filler direct contact (filler‐filler contact), and another is formed by polymer chain anchored between neighbor fillers (filler‐rubber network) . Usually, the filler‐filler network is harmful to the dynamic mechanical properties of the sample, while the filler‐rubber network is beneficial to the dynamic mechanical properties of the sample.…”

“…One is formed by filler-filler direct contact (fillerfiller contact), and another is formed by polymer chain anchored between neighbor fillers (filler-rubber network). 33,34 Usually, the filler-filler network is harmful to the dynamic mechanical properties of the sample, while the filler-rubber network is beneficial to the dynamic mechanical properties of the sample. RPA measurements could exhibit the filler network in the system, and the interfacial interaction between BCC, silica, and SBR matrix.…”