Lightweight and highly absorptive expanding TPU composite foams for electromagnetic interference shielding with excellent electrical insulation and low thermal conductivity

• A facile fabrication process was developed for E-TPU@Ag/PDMS composites. • High electromagnetic shielding effectiveness • The shielding mechanism of the composites is primarily absorption-dominated. • These composites demonstrate excellent electrical insulation properties. • The E-TPU@Ag/PDMS composites possess high strength, low density, and excellent mechanical flexibility. • The composites also show good thermal insulation and hydrophobicity. With the rapid advancement of modern communication and electronic technologies, there is an increasing demand for polymer composites integrating multiple functionalities, such as electromagnetic interference (EMI) shielding, thermal insulation, electrical insulation, and light weight. However, achieving synergistic optimization of these properties in a single polymer system remains a significant challenge. Expanded thermoplastic polyurethane (E-TPU) beads are produced from thermoplastic polyurethane (TPU) via a physical foaming process. This material combines high mechanical strength, excellent wear resistance, low density, high elasticity, energy absorption, and good thermal insulation properties, along with environmental friendliness. It demonstrates considerable potential for a wide range of engineering applications. In this study, a composite material denoted as E-TPU@Ag/PDMS was fabricated via a facile spraying process. Herein, E-TPU@Ag serves as the conductive component to construct a conductive network, while polydimethylsiloxane (PDMS) acts as both a binder and an insulating protective layer. Benefiting from a segregated structural design, the composite exhibits outstanding comprehensive performance in the X-band (8.2–12.4 GHz): an electromagnetic interference shielding effectiveness (EMI SE) of 53.3 dB, a high absorption coefficient (A) of 0.74, a volume resistivity exceeding 10¹¹ Ω·cm, a density of 0.51 g/cm³, and a thermal conductivity of 0.19 W·m⁻¹·K⁻¹. This work provides a novel strategy for designing multifunctional composites that combine high shielding efficiency, strong absorption capacity, excellent electrical insulation, efficient thermal isolation, and light weight.