Atomistic Insights on the Rheological Property of Polycaprolactone Composites with the Addition of Graphene

Abstract

Although polymer composites reinforced by graphene have been researched for almost two decades, the processing challenges caused by viscosity remains, especially for 3D printing. [3] Many experimental works have been conducted to assess the rheological properties of graphene reinforced composites, covering various factors such as weight/volume fraction, dispersion, surface modification, and shear rate. [4] However, the influence of the graphene size has not been systematically studied experimentally due to the intrinsic complexities and challenges for sample preparation with controlled micro/nanoscale features. In particular, the influence of 2D nanoscale fillers on the rheological properties of polymer composites remains unclear. With such experimental difficulties, numerical modeling or simulation becomes a powerful tool to probe the rheological properties of polymer composites at the micro and nano scales. Different modeling approaches have been developed for such purposes, such as the multiscale method, coarse grain (CG) method, and molecular dynamic (MD) simulation. For instance, the multiscale method has been well-developed to predict the mechanical performance of carbon-reinforced composites. [5] Compared with the multiscale and CG methods, MD simulation can exploit the influences from nanoscale reinforcements on the rheological properties of polymer composites at an atomistic level. Many works have investigated the effect of the size of nanoparticle reinforcements on the composite's viscosity based on MD simulations. Grant et al. [6] identified that viscosity could be influenced by the nanoparticle volume fraction, interface area, and the interaction between particle and polymer. Francis et al. [7] found that the composite viscosity would decrease when small particles aggregate into a large cluster. More recent work found that the composite viscosity depends on the relation between particle size and polymer entanglement length. Jagannathan et al. [8] discovered that if the particle size is smaller than the polymer entanglement length, the composite viscosity will reduce and vice versa. Ting et al. [9] chose a group of particles smaller than the polymer entanglement length and found that the viscosity increases with increasing particle size while the interaction between the polymer and particle changes from slippery to sticky. Overall, when the particle size is around the polymer entanglement length, the viscosity increases with To facilitate the biomedical applications of biocomposites, researchers have used different types of fillers to enhance their mechanical properties. However, the addition of fillers not only changes the mechanical performance of the biocomposites, but also affects their printability, that is, their rheological properties. With the aid of atomistic simulations, this work investigates the influence of graphene size and aggregation on the rheological properties of polycaprolactone (PCL) composites. For the same weight ratio, increasing the graphene size causes the viscosity of the ...

Resolving the dynamic properties of entangled linear polymers in non-equilibrium coarse grain simulation with a priori scaling factors

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