Effect of nanoparticle aspect ratio on Joule heating of graphite-based bucky-paper

In the field of civil infrastructures, ice formation on bridges and roofs represents a problem that hinders the praticability and the lightning of load-bearing structures. In this paper, the manufacturing of graphite-based bucky-paper infiltrated with a very low amount of thermoplastic polymer is proposed. The bucky-paper is able to act as heating element to prevent the ice formation since 2D nanostructures, like bucky-paper, or graphene-based films, can satisfy requirements such as structural compatibility, flexibility, mechanical reinforcement, and adaptability in multilayered composite structures. In this work, expanded graphite (EG) based film heaters infiltrated with PVA are produced by a green solvent casting process, using a biodegradable polymer. The resulting film heater offers an excellent combination of mechanical electrical and thermal performance. In particular, the effect of aspect ratio of two 2D fillers on the film properties has been investigated. Structural and morphological analysis (not reported here) showed that EG2 filler is characterized by an aspect ratio of about 1 order of magnitude higher than EG1. Thermal analysis performed by DMA, TGA analysis highlights that the film heater filled with the nanoparticles with a higher aspect ratio (EG2) manifests higher thermal stability and mechanical properties compared to EG1 system. Moreover, the higher electrical conductivity of the EG2 based system results in a best heating performance. In fact, for the same applied voltage values, EG2 system achieves higher temperature values. The thermal images, obtained by infrared camera, show that, for the same applied power, the EG2 based system is characterized by a more homogeneous surface temperature distribution compared with the EG1 system. The uniformity is visible in the central area of the film, which presents the same color tone. An increase in the aspect ratio of the filler allows obtaining an increase in the de-icing performance of the heater film. It generates higher temperature values, using lower applied voltages. This result is crucial when considering the applicability of the heating system in the sector of civil engineering, like de-icing of roofs, bridges and repairs of buildings belonging to the artistic heritage, where it is not possible to massively intervene on the supporting structures.