关键词: 片状羰基铁, 聚多巴胺, 硅烷偶联剂, 无纺布, 吸波材料

Abstract: The rapid development of electronic information technology has significantly improved human lifestyles, while also contributing to the increasing issue of electromagnetic radiation pollution. Electromagnetic wave-absorbing materials are effective for mitigating electromagnetic radiation pollution. They can be classified into magnetic loss, dielectric loss, and resistive loss types based on their loss mechanisms. Flaky carbonyl iron (FCI) is a typical magnetic loss-type absorber, widely studied for its shape anisotropy and favorable magnetic response in the microwave frequency range. However, traditional carbonyl iron particles tend to agglomerate in polymer matrices due to their high surface energy. This leads to interfacial discontinuities and structural defects, negatively affecting both the mechanical properties and the electromagnetic wave attenuation capacity of the composites. Studies have shown that constructing surface modification layers with reactive or wettable functional groups on magnetic particles can effectively mitigate agglomeration, enhancing their dispersion stability and interfacial compatibility within the polymer matrix. To address the poor dispersion stability of FCI in waterborne polyurethane systems, FCI particles were sequentially modified with polydopamine (PDA) and dodecyltrimethoxysilane (DTMS) to obtain FCI-PDA@DTMS. The morphology, structure, and stability behavior of the modified sample FCI-PDA@DTMS in the waterborne polyurethane system were also investigated. On this basis, the FCI-PDA@DTMS/waterborne polyurethane functional coating (FPM/PU) was combined with non-woven fabric (NW) to prepare the FPM/PU-NW composite. The electromagnetic parameters and microwave absorption properties were evaluated using a vector network analyzer. Results indicate that FCI-PDA@DTMS exhibited improved dispersion stability in the waterborne polyurethane matrix. When the filler content reached 70%, the FPM/PU-NW sample with a thickness of 1.29 mm achieved a minimum reflection loss of -65.64 dB at 12.74 GHz, with an effective absorption bandwidth of 7.27 GHz. The enhanced microwave absorption performance can be mainly attributed to the improved dispersion of the modified FCI in the PU matrix, which facilitates the formation of a magnetic-dielectric synergistic loss network and promotes interfacial polarization and magnetic loss. In addition, the uniformly dispersed flaky particles are embedded within the three-dimensional fibrous skeleton of the nonwoven fabric, effectively extending the propagation paths of electromagnetic waves and enhancing multiple reflections and scattering, thereby contributing to the overall absorption performance of the composite.

Key words: flake carbonyl, iron, polydopamine, silane coupling agent, nonwoven fabric, wave-absorbing material