Sustainable polyimide-based nanocomposite materials for space antenna applications

Introduction Advanced polymeric materials for space applications must ensure high thermal stability, chemical resistance, controlled surface properties and reliable adhesion to inorganic substrates, while minimizing environmental impact. Polyimides represent a promising class of materials due to their intrinsic thermal and mechanical performance. This work investigates nanocomposite materials based on purified polyimide P84, re-solubilized in a green solvent, dimethyl isosorbide, and reinforced with two-dimensional nanofillers, with the aim of tailoring their thermal and surface properties for potential use in coating applications for antenna components. Material and Methods Commercial P84 polyimide was purified and re-dissolved in DMI to obtain homogeneous polymer solutions. Two-dimensional fillers, graphene and hexagonal boron nitride, and their hybrid combinations were added at 1, 3 and 5 wt%. Nanocomposite samples (average thickness ~80 μm) were obtained by solution casting followed by solvent evaporation in oven. A multistep thermal drying protocol was optimized, including degassing under vacuum, stepwise air drying from 60 °C to 110 °C, and a final vacuum treatment to avoid solvent entrapment and bulk inhomogeneities. Nanocomposites were characterized by FTIR spectroscopy, differential scanning calorimetry, water contact angle and surface free energy analysis. Results and Discussion FTIR analysis confirmed the characteristic functional groups of aromatic polyimides and the absence of new chemical bonds upon filler addition. DSC measurements demonstrated that the incorporation of graphene, h-BN and hybrid fillers increases the glass transition temperature (Tg), with values ranging from 240 °C to 253 °C, well above the typical space mission thermal window (−220 °C to +190 °C). This confirms the thermal stability of the nanocomposites under relevant operating conditions. The observed variations in Tg and in heat capacity values can be ascribed to the filler-induced restriction of polymer chain mobility. Surface analyses revealed decreasing water contact angles and total surface free energy with increasing filler content. The SFE values (32–38 mJ m⁻²) are suitable for effective substrate wetting and adhesion to inorganic substrates such as glass and quartz. Overall, the incorporation of 2D nanofillers enables effective tuning of the thermo-physical properties of P84-based nanocomposites, highlighting their strong potential for space applications.