Novel core-shell composite material based on polyacrylic acid salt and polyaniline for infrared camouflage applications

Infrared stealth materials that are lightweight and offering effective thermal camouflage are increasingly needed for advanced defense and sensing applications. Core-shell polymeric composites exhibit high performance thanks to strong interfacial interaction, multiple absorption mechanisms, and low density. This research presents a successful attempt at the preparation of lightweight infrared (IR) stealth polymeric core-shell composite material. The mechanism for thermal camouflage is based on absorbing the incoming thermal signals and then emitting them outside the atmospheric windows (wavelengths of 5-8 μm and 8-14 μm) via a broadband absorption/emission mechanism. Novel core-shell composite materials were prepared, using the in situ polymerization method to form a a shell of polyaniline (PANI) with two types of core materials, poly acrylic acid salt (PAAS) and polyacrylonitrile (PAN) with PANI weight ratios of 10%, 15%, and 20%. Additionally, physical mixture of PANI and PAAS were also tested to highlight the role of the microstructure of the material in the camouflage performance. The prepared samples were characterized structurally and morphologically using Fourier transform infrared (FT-IR) spectroscopy, contact angle measurement, and scanning electron microscopy (SEM)) and functionally, by measuring the specific electrical conductivity and thermal imaging of the samples. The findings show that the physical mixture samples did not work as stealth materials, while the two prepared composite materials had promising camouflage properties, which correlates with the proposed stealth mechanism. It is found that the composite material of PANI@PAAS gives better camouflage properties than PANI@PAN. Finally, the performance of the prepared composite material PANI@PAAS was superior to that of recently reported hybrid composite polymer-ceramics materials, that have relatively high density. In terms of thermal differences, achieving ΔT = 0 °C at 38 °C. Therefore, PANI@PAAS holds promise for infrared stealth applications that require lightweight and flexibility.