Mechanical, Wear and Thermal Behavior of Polyethylene Blended with Graphite Treated in Ball Milling

Breaking graphite through a ball-milling process: the thermal conductivity and mechanical properties of polyethylene composites

Exfoliated graphite platelets (EGPs) have attracted extensive attention owing to their exceptional combinations of thermal conductivity and mechanical properties. Mechanical exfoliation is a facile and high-throughput approach to produce single-layer or few-layer graphite platelets. Herein, octadecylamine (ODA)-grafted EGP (ODA@EGP) and subsequent polyethylene/ODA@EGP (PE/ODA@EGP) composites with different contents of ODA@EGPs were successfully prepared via ball-milling and melt-mixing methods, respectively. The thermal conductivity, crystallinity, and mechanical properties of the composites were investigated using tensile tests, the hot-wire method, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, and thermogravimetric analysis (TGA). The results demonstrated that the thermal conductivity, mechanical properties, and thermal stability of the composites can be improved by regulating the additive contents of ODA@EGPs. When the content of ODA@EGPs was 10 wt%, the thermal conductivity of the composite reached up to 1.276 W (m-1 K-1), which is 216% higher than that of bare PE, while the tensile strength of the composite was 38.4% higher than that of PE. Additionally, thermal decomposition temperature increased by 16.2 °C. Therefore, the PE/ODA@EGP nanocomposites have great application potential in thermal management.

Polymer-Assisted Graphite Exfoliation: Advancing Nanostructure Preparation and Multifunctional Composites

Exfoliated graphite (ExG) embedded in a polymeric matrix represents an accessible, cost-effective, and sustainable method for generating nanosized graphite-based polymer composites with multifunctional properties. This review article analyzes diverse methods currently used to exfoliate graphite into graphite nanoplatelets, few-layer graphene, and polymer-assisted graphene. It also explores engineered methods for small-scale pilot production of polymer nanocomposites. It highlights the chemistry involved during the graphite intercalation and exfoliation process, particularly emphasizing the interfacial interactions related to steric repulsion forces, van der Waals forces, hydrogen bonds, π-π stacking, and covalent bonds. These interactions promote the dispersion and stabilization of the graphite derivative structures in polymeric matrices. Finally, it compares the enhanced properties of nanocomposites, such as increased thermal and electrical conductivity and electromagnetic interference (EMI) shielding applications, with those of neat polymer materials.

Rare-Earth Oxides as Alternative High-Energy Photon Protective Fillers in HDPE Composites: Theoretical Aspects

This work theoretically determined the high-energy photon shielding properties of high-density polyethylene (HDPE) composites containing rare-earth oxides, namely samarium oxide (Sm₂O₃), europium oxide (Eu₂O₃), and gadolinium oxide (Gd₂O₃), for potential use as lead-free X-ray-shielding and gamma-shielding materials using the XCOM software package. The considered properties were the mass attenuation coefficient (µ_m), linear attenuation coefficient (µ), half value layer (HVL), and lead equivalence (Pb_eq) that were investigated at varying photon energies (0.001–5 MeV) and filler contents (0–60 wt.%). The results were in good agreement (less than 2% differences) with other available programs (Phy-X/PSD) and Monte Carlo particle transport simulation code, namely PHITS, which showed that the overall high-energy photon shielding abilities of the composites considerably increased with increasing rare-earth oxide contents but reduced with increasing photon energies. In particular, the Gd₂O₃/HDPE composites had the highest µ_m values at photon energies of 0.1, 0.5, and 5 MeV, due to having the highest atomic number (Z). Furthermore, the Pb_eq determination of the composites within the X-ray energy ranges indicated that the 10 mm thick samples with filler contents of 40 wt.% and 50 wt.% had Pb_eq values greater than the minimum requirements for shielding materials used in general diagnostic X-ray rooms and computerized tomography rooms, which required Pb_eq values of at least 1.0 and 1.5 mmPb, respectively. In addition, the comparisons of µ_m, µ, and HVL among the rare-earth oxide/HDPE composites investigated in this work and other lead-free X-ray shielding composites revealed that the materials developed in this work exhibited comparable X-ray shielding properties in comparison with that of the latter, implying great potential to be used as effective X-ray shielding materials in actual applications.