Dispersion and re-agglomeration of graphite nanoplates in polypropylene melts under controlled flow conditions

Abstract

a b s t r a c tThe kinetics of GnP dispersion in polypropylene melt was studied using a prototype small scale modular extensional mixer. Its modular nature enabled the sequential application of a mixing step, melt relaxation, and a second mixing step. The latter could reproduce the flow conditions on the first mixing step, or generate milder flow conditions. The effect of these sequences of flow constraints upon GnP dispersion along the mixer length was studied for composites with 2 and 10 wt.% GnP. The samples collected along the first mixing zone showed a gradual decrease of number and size of GnP agglomerates, at a rate that was independent of the flow conditions imposed to the melt, but dependent on composition. The relaxation zone induced GnP re-agglomeration, and the application of a second mixing step caused variable dispersion results that were largely dependent on the hydrodynamic stresses generated.

Electrically Conductive Polyetheretherketone Nanocomposite Filaments: From Production to Fused Deposition Modeling

“…Materials for FDM applications should also present good morphology stability since they will be successively subjected to compounding, filament extrusion, and 3D printing, all stages involving heating above the polymer melt temperature and flow. Evidence of re-agglomeration during re-heating and flow of polymer/CNT and polymer/GnP nanocomposites was well documented, as well as its influence on the resulting electrical performance [41,42,43,44]. The nanocomposites’ morphological stability upon heating was estimated by submitting the nanocomposite filaments to additional thermomechanical cycle(s) to observe eventual variations in the properties.…”

Dispersion of Graphite Nanoplates in Polypropylene by Melt Mixing: The Effects of Hydrodynamic Stresses and Residence Time

“…The dispersion experiments were performed using the following materials [ 20 ]: As matrix, a polypropylene copolymer (PP) (Icorene CO14RM from Ico Polymers, France, with a melt flow index of 13.0 g/10 min @190 C/ 2.16 kg and a density of 0.9 g/cm ); As filler, graphite nanoplates (GnP) (Grade C-750 from XG Sciences, Inc., Lansing, MI, USA, with a size distribution ranging from very small (100 nm) to relatively large flakes (1–2 m)). …”

“…Once an experiment is completed, the device can be quickly removed from the rheometer, and opened to collect samples for subsequent morphological characterization. In order to study both dispersion and relaxation phenomena, the design was later modified by inserting a relaxation chamber (where the melt is subjected to quasi-quiescent conditions) between two series of stacked rings with alternating larger and smaller inner diameters [20]. Numerical methods can access pressure, velocity, temperature and stress profiles in a given flow channel.…”

“…This work combines experimental and numerical data to better understand the evolution of dispersion of graphite nanoplates in the mixing device consisting of a series of stacked rings with an equal outer diameter and alternating larger and smaller inner diameters ( Figure 1 d). This mixer was used to manufacture nanocomposites containing carbon nanofibers, carbon nanotubes or graphite nanoplates, yielding levels of dispersion comparable to those typically attained with twin-screw extruders [ 19 , 20 , 27 ]. The numerical simulations considered both inelastic and viscoelastic fluids.…”

Facile preparation of polyamide 6/exfoliated graphite nanoplate composites via ultrasound‐assisted processing

“…Recently, significant attention has been focused on preparing PA6/graphene nanocomposites due to their excellent mechanical and conductive properties, which give the nanocomposite a large application potential in the microelectronic packaging, automotive, and aerospace industries . Unfortunately, the current low throughput and high cost of graphene gravely restricts the development of such high‐performance nanocomposite in industrial applications.…”