Study on the Mechanism, Properties, and Application as EMW-Absorbing Matrix Materials of Protonic Acid-Doped Heat-Resistant Conductive Polyurethanes

Protonic acid doping of heat-resistant and conductive polyurethane elastomers (PCPU) can significantly enhance their electrical conductivity. By doping with different types of protonic acids and varying molar amounts of camphorsulfonic acid (CSA), the doping mechanism and molecular structure changes of PCPU were systematically investigated using multiple characterization techniques such as Fourier-transform infrared (FTIR), X-ray diffraction (XRD), UV–vis and so on. Meanwhile, the effects of protonic acid doping on the thermal stability and mechanical properties of PCPU were further evaluated using thermo-gravimetric analysis (TGA), Differential scanning calorimetry (DSC), and stress–strain testing. Although protonic acid doping reduces the thermal stability and fracture strength of PCPU, the acid-doped PCPU can form an ionic gel network, which facilitates the uniform dispersion of electromagnetic wave (EMW) absorbers within the matrix. Additionally, protonic acid doping endows the electromagnetic wave absorbing materials (EMWAMs) prepared from PCPU and nanographite (Gr) with tunable electromagnetic matching characteristics and enhanced wave attenuation capabilities, exhibiting excellent EMW absorption performance across a broad frequency range. For instance, the 10% Gr-PCPU-2CSA composite achieves a minimum reflection loss of −27.98 dB and an effective absorption bandwidth of 5.3 GHz at a thickness of 2.5 mm. Therefore, this study provides novel insights for the development of high-performance EMW-absorbing matrix materials.