Abstract
The poor thermal conductivity of polymer composites has long been a deterrent to their increased use in high-end aerospace or defence applications. This study describes a new approach for the incorporation of graphene in an epoxy resin, through the addition of graphene as free-standing film in the polymeric matrix. The electrical and thermal conductivity of composites embedding two different free-standing graphene films was compared to composites with embedded carbon nanotube buckypapers (CNT-BP). Considerably higher thermal conductivity values than those achieved with conventional dispersing methods of graphene or CNTs in epoxy resins were obtained. The characterisation was complemented with a study of the structure at the microscale by cross-sectional scanning electron microscopy (SEM) images and a thermogravimetric analysis (TGA). The films are preconditioned in order to incorporate them into the composites, and the complete manufacturing process proposed allows the production and processing of these materials in large batches. The high thermal conductivity obtained for the composites opens the way for their use in demanding thermal management applications, such as electronic enclosures or platforms facing critical temperature loads.Graphical abstractGraphene composites obtained by integrating graphene free-standing films in epoxy resin exhibited higher thermal conductivity values than composites with carbon nanotube buckypapers.
Highlights
Thermal management of aerospace structures is extremely important for many applications including space or defence platforms, re-entry vehicles, propulsion systems, electronics or high energy systems
Three free-standing films based on carbon nanostructures—commercial graphene film made by Nanografi, carbon nanotube buckypapers (CNT-BP) manufactured at Tecnalia and thermally-reduced graphene oxide (GO) film produced by Graphenea Nanomaterials S.A.— were embedded in a commercial liquid epoxy-based resin (Resoltech 1800/1805) to enhance their thermal conductivity
Two free-standing graphene films— graphene film made by Nanografi and graphene oxide (GO) film with a thermal treatment at 200 °C for 18 h made by Graphenea—were compared to carbon nanotube buckypaper (CNT-BP) manufactured by Tecnalia
Summary
Thermal management of aerospace structures is extremely important for many applications including space or defence platforms, re-entry vehicles, propulsion systems, electronics or high energy systems. The inherent poor thermal conductivity of polymer composites, which are the most widely used materials in aerospace structures due to their high strength-to-weight ratio, is a significant drawback in such kind of applications. Several research groups have reported enhanced thermal conductivity values for dispersed graphene/epoxy resins through blending methods [2, 3]. These methods include conventional mixing methods such as three roll milling or calendaring and high shear mixing processes. The analysis of these results shows that thermal conductivity of polymerbased composites is enhanced with the increased loading of fillers. The incorporation of high concentrations of graphene is difficult and hard to perform, due to the increase in the polymer viscosity
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