Functionalized MXene as a multifunctional crosslinker for reinforced novel waste PET-depolymerized monomer-based polyurethane composites with electrical conductivity and electromagnetic shielding effect

The construction of functional crosslinked polyurethane composites based on the depolymerized monomer bis(2-hydroxyethyl) terephthalate (BHET) from abandoned PET can achieve high-value application of BHET. Herein, polyurethane composites (PU/MXene-s-BHET) with functional crosslinked network structure were prepared via bio-based polyol BHET modified bio-based hydrogenated dimer acid (PBHDA) and functionalied MXene (MXene-s-BHET). MXene-s-BHET was fabricated through 3-isocyanatopropyltriethoxysilane (IPTS) as a surface modifier between BHET and MXene by covalent bonds and hydrogen bonds, thereby enabling crosslinking effect. MXene-s-BHET can not only form crosslinked network structure with the PU chains to enhance the interfacial bonding between filler and PU, but also promote the fine dispersion for the filler in matrix on endow composites with remarkable mechanical performance and functionality. Only containing 2 wt% MXene-s-BHET endows PU/MXene-s-BHET2 with a high electrical conductivity of 9.65 × 10⁻³ S/m, thermal conductivity of 0.687 W m⁻¹ K⁻¹ (increased by 271.4 %), and electromagnetic interference shielding efficiency of 26.8 dB in the X-band. Furthermore, the PU/MXene-s-BHET2 composites exhibit excellent mechanical properties (elongation at break of 472.3 % and tensile strength of 20.1 MPa), storage modulus and heat resistance. Hence, this work will open new path for promoting the high-value recycling of resources and the innovation for functional polyurethanes.