Vertically Aligned and Interconnected Graphite and Graphene Oxide Networks Leading to Enhanced Thermal Conductivity of Polymer Composites

Natural graphite flakes possess high theoretical thermal conductivity and can notably enhance the thermal conductive property of polymeric composites. Currently, because of weak interaction between graphite flakes, it is hard to construct a three-dimensional graphite network to achieve efficient heat transfer channels. In this study, vertically aligned and interconnected graphite skeletons were prepared with graphene oxide serving as bridge and support via freeze-casting method. Three freezing temperatures were utilized, and the resulting graphite and graphene oxide network was filled in a polymeric matrix. Benefiting from the ultralow freezing temperature of -196 °C, the network and its composite occupied a more uniform and denser structure, which lead to enhanced thermal conductivity (2.15 W m-1 K-1) with high enhancement efficiency and prominent mechanical properties. It can be significantly attributed to the well oriented graphite and graphene oxide bridges between graphite flakes. This simple and effective strategy may bring opportunities to develop high-performance thermal interface materials with great potential.

Designable core-shell graphite particles for thermally conductive and electrically insulating polymer composites

Electrically insulating graphite particles were prepared by coating graphite with electrically insulating materials via a two-step mechanical mixing process. Graphite particles were treated with a binder in the 1st mixing process and coated with an electrically insulating particle in the 2nd mixing process under high shear forces within a short processing time (below 1 min). Micron-sized graphite particles were successfully coated with various inorganic particles of appropriate particle diameter. Talc and boron nitride exhibited good affinities with graphite and formed effective coating layers to render reliable electrical insulation. Graphite coated with talc and boron nitride exhibited a high volume resistivity, greater than 109 Ω cm. The insulating property was retained even after compounding and moulding the coated graphite particles with a polymer. The two-step coating process under high shear forces is a promising method for production of coated graphite particles.

Learning from Natural Nacre: Constructing Layered Polymer Composites with High Thermal Conductivity

Inspired by the microstructures of naturally layered and highly oriented materials, such as natural nacre, we report a thermally conductive polymer composite that consists of epoxy resin and Al₂O₃ platelets deposited with silver nanoparticles (AgNPs). Owing to their unique two-dimensional structure, Al₂O₃ platelets are stacked together via a hot-pressing technique, resulting in a brick-and-mortar structure, which is similar to the one of natural nacre. Moreover, the AgNPs deposited on the surfaces of the Al₂O₃ platelets act as bridges that link the adjacent Al₂O₃ platelets due to the reduced melting point of the AgNPs. As a result, the polymer composite with 50 wt % filler achieves a maximum thermal conductivity of 6.71 W m^-1 K^-1. In addition, the small addition of AgNPs (0.6 wt %) minimally affects the electrical insulation of the composites. Our bioinspired approach will find uses in the design and fabrication of thermally conductive materials for thermal management in modern electronics.

Synergistic charring effect of triazinetrione-alkyl-phosphinate and phosphaphenanthrene derivatives in epoxy thermosets

The component synergistic charring effect of a TAHP/TAD system caused more balanced flame-retardant actions in the gaseous phase and condensed phase.

A one-step process employing various amphiphiles for an electrically insulating silica coating on graphite

Herein, we report new way and mechanism to completely coat graphite (3–550 μm) with a silica layer within 12 hours.

Reasons and remedies for the agglomeration of multilayered graphene and carbon nanotubes in polymers

One of the main issues in the production of polymer nanocomposites is the dispersion state of filler as multilayered graphene (MLG) and carbon nanotubes (CNTs) tend to agglomerate due to van der Waals forces. The agglomeration can be avoided by using organic solvents, selecting suitable dispersion and production methods, and functionalizing the fillers. Another proposed method is the use of hybrid fillers as synergistic effects can cause an improvement in the dispersion state of the fillers. In this review article, various aspects of each process that can help avoid filler agglomeration and improve dispersion state are discussed in detail. This review article would be helpful for both current and prospective researchers in the field of MLG- and CNT-based polymer nanocomposites to achieve maximum enhancement in mechanical, thermal, and electrical properties of produced polymer nanocomposites.

Mechanical, Thermal, and Electrical Properties of Graphene-Epoxy Nanocomposites-A Review

Monolithic epoxy, because of its brittleness, cannot prevent crack propagation and is vulnerable to fracture. However, it is well established that when reinforced—especially by nano-fillers, such as metallic oxides, clays, carbon nanotubes, and other carbonaceous materials—its ability to withstand crack propagation is propitiously improved. Among various nano-fillers, graphene has recently been employed as reinforcement in epoxy to enhance the fracture related properties of the produced epoxy–graphene nanocomposites. In this review, mechanical, thermal, and electrical properties of graphene reinforced epoxy nanocomposites will be correlated with the topographical features, morphology, weight fraction, dispersion state, and surface functionalization of graphene. The factors in which contrasting results were reported in the literature are highlighted, such as the influence of graphene on the mechanical properties of epoxy nanocomposites. Furthermore, the challenges to achieving the desired performance of polymer nanocomposites are also suggested throughout the article.