Nucleation of the β-polymorph in Composites of Poly(propylene) and Graphene Nanoplatelets

Abstract

The effects of graphene nanoplatelets (GNPs) on the nucleation of the β-polymorph of polypropylene (PP) were studied when melt-mixed at loadings of 0.1–5 wt % using a laboratory scale twin-screw (conical) extruder and a twin-screw (parallel) extruder with L/D = 40. At low GNP loadings (i.e., ≤0.3 wt %), the mixing efficiency of the extruder used correlated with the β-nucleating activity of GNPs for PP. GNP agglomeration at low loadings (<0.5 wt %) resulted in an increase in the β-phase fraction (Kβ) of PP, as determined from X-ray diffraction measurements, up to 37% at 0.1 wt % GNPs for composites prepared using a laboratory scale twin-screw (conical) extruder. The level of GNP dispersion and distribution was better when the composites were prepared using a 16-mm twin-screw (parallel) extruder, giving a Kβ increase of 24% upon addition of 0.1 wt % GNPs to PP. For GNP loadings >0.5 wt %, the level of GNP dispersion in PP did not influence the growth of β-crystals, where Kβ reached a value of 24%, regardless of the type of extruder used. From differential scanning calorimetry (DSC) measurements, the addition of GNPs to PP increased the crystallization temperature (Tc) of PP by 14 °C and 10 °C for the laboratory scale extruder and 16-mm extruder, respectively, confirming the nucleation of PP by GNPs. The degree of crystallinity (Xc%) of PP increased slightly at low GNP additions (≤0.3 wt %), but then decreased with increasing GNP content.

Fused filament fabrication of polyetheretherketone/multiwalled carbon nanotube nanocomposites: the effect of thermally conductive nanometric filler on the printability and related properties

“…The thermal properties of the polymer/CNT composites reported in the literature are relatively low compared with expectation; most of the published results indicate that the enhancement in the thermal conductivity of polymer/CNT composites does not achieve the theoretical prediction. The concentration dependence of the thermal conductivity of polymer/CNT composites does not reveal percolation behavior in the vicinity of the electrical percolation concentration 40 primarily due to the interfacial thermal resistance that impedes phonon transfer and thus the heat conduction in the polymer 41 . An extensive review 37 on polymer/CNT thermal conductivity explains the dependence of the thermal conductivity on different CNT properties and the roles of the particle–polymer and particle–particle interfaces.…”

3D Printing‐Enabled Nanoparticle Alignment: A Review of Mechanisms and Applications

“…FDM was the very first 3D printing method to achieve the alignment of reinforcement fillers in composites. There is so much research in different polymer/nanoparticle systems that their applications cannot be exhausted, [8,30,263] and just a few gen eral examples are summarized here. The particles' alignment (e.g., graphene and boron nitride platelets) was first applicable in throughplane thermal conductivity (TPTC).…”

“…Filaments used for FDM are mostly from extru ders. [30,32,84,246,263] Singlescrew extrusion is efficient and cost efficient for producing filaments of appropriate diameters for 3D printing. Optimization of the various processing parameters of screw speed, barrel temperature, die temperature, water tank temperature, and takeup unit speed will fabricate continuous, homogeneous, and robust filaments.…”

“…Aligned particles generate a path for directing efficient phonon transport. Particles for building a thermally conductive path include Cu, [473] graphene, [263,474] CNT, [475] CF, [476] alumina, [477] and BN. [478,479] Among them, boron nitride layers or platelets can achieve improvements in thermal properties.…”

Study on preparation and field induction mechanism of organic silicon composites based on aligned carbon nanotubes

“…Therefore, carbon nanotubes have been proved to be one of ideal filler for polymer matrix nanocomposites. [12,13] Due to the strong van der Waals force, carbon nanotubes tend to agglomerate in the polymer, limiting the performance. Chemical modification can help to solve the aggregation of carbon nanotubes and improve their compatibility with polymers.…”