High-Performance TPU/MWCNT Composites via In-Situ Polymerization for Ultrathin and Broadband Electromagnetic Absorption with Enhanced Mechanical Properties

This paper presents a comprehensive analysis of TPU/MWCNT absorbing composites, which were synthesized through the in-situ polymerization of polycarbonate diol (PCDL), 4,4-diphenylmethane diisocyanate (MDI), 1,4-butanediol (BDO), and hydroxylated multi-walled carbon nanotubes (MWCNT) in varying amounts. The study investigates the effects of MWCNT addition on the microstructure, mechanical properties, thermal stability, and wave absorption performance of the composites. Compared to neat TPU, the composite with 6 wt % MWCNT demonstrates an increase in tensile strength of 3.4 MPa (approximately 8.7%) and an elongation-at-break enhancement of 118%. Additionally, the temperature corresponding to 5% mass loss increases modestly from 308 °C to 324.5 °C. X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images confirm that the MWCNT structure is well-preserved within the TPU and exhibits good dispersion. The uniform distribution of MWCNT in the TPU facilitates the formation of effective conductive pathways in the composites, resulting in significant dielectric loss for incident electromagnetic waves. The composites containing 6% MWCNT achieve full-frequency absorption of X-band electromagnetic waves, with a maximum absorption of -20.78 dB and a matching thickness of only 1.1 mm. Furthermore, the incorporation of MWCNT enhances the mechanical properties of the composites while exerting minimal impact on the thermal characteristics of TPU.