Summary of advances in structural design and fabrication of homogeneous, multilayer, porous, hybrid, and magnetic Ti₃C₂T_x/polymer composites, regulating the electromagnetic parameters for green absorption electromagnetic interference shielding.

Absorption-dominated electromagnetic interference (EMI) shielding is attained by improving impedance matching and conductivity through structural design. Polyvinylidene fluoride (PVDF)–Ti₃C₂T_x MXene–single-walled carbon nanotubes (SWCNTs) composites with layered heterogeneous conductive fillers and segregated structures were prepared through electrostatic flocculation and hot pressing of the PVDF composite microsphere-coated MXene and SWCNTs in a layer-by-layer fashion. Results suggest that the heterogeneous fillers improve impedance matching and layered coating, and hot compression allows the MXene and SWCNTs to form a continuous conducting network at the PVDF interface, thereby conferring excellent conductivity to the composite. The PVDF-MXene-SWCNTs composite showed a conductivity of 2.75 S cm⁻¹ at 2.5% MXene and 1% SWCNTs. The EMI shielding efficiency (SE) and contribution from absorption loss to the total EMI SE of PVDF-MXene-SWCNTs were 46.1 dB and 85.7%, respectively. Furthermore, the PVDF-MXene-SWCNTs composite exhibited excellent dielectric losses and impedance matching. Therefore, the layered heteroconductive fillers in a segregated structure optimize impedance matching, provide excellent conductivity, and improve absorption-dominated electromagnetic shielding.

Ecofriendly flame-retardant polystyrene (PS) composites were developed using the synergistic effects of phytic acid (PA), polyethyleneimine (PEI), and expandable graphite (EG). PA was chemically hybridized with PEI, and the hybrid (PAE) was incorporated into PS together with EG. The flame-retardant performances of the resulting composites were evaluated using the limiting oxygen index (LOI), UL-94 vertical burning test, and cone calorimetry test. The strong interaction between EG and PAE provided an effective barrier against heat and oxygen, thereby improving the flame retardancy. The best-performing composite (PA:PEI:EG = 1:1:1 (w/w/w), total flame-retardant loading = 10 parts per 100 parts of PS) exhibited an LOI of 27.7% and a UL-94 V-0 rating. The peak heat release rate (148.8 kW/m²) and total heat release (91.2 MJ/m²) of this composite were lower than those of pure PS by 79.2% and 34.0%, respectively. This study provides guidelines for the production of flame-retardant PS and other polymeric materials.

Silver nanowires (AgNWs) have excellent electrical conductivity and nano-sized effects and have been widely used as a high-performance electromagnetic shielding material. However, silver nanowires have poor mechanical properties and are prone to fracture during the preparation of composite materials. In this study, PVDF/rGO/AgNW composites with a segregated structure were prepared using low-pressure compression molding and the AgNW-backfilling process. The low-pressure compression of the composite significantly improves its electromagnetic shielding performance because the low-pressure process can maintain the AgNWs’ integrity. The backfilled AgNWs played a vital role in increasing the path of electromagnetic wave propagation and the absorption of electromagnetic waves. The backfilled amount of AgNWs was only 1 wt%, which increased the composite material’s conductivity by one order of magnitude. The total electromagnetic interference shielding (SE_T) of the composite materials increased by 23.3% from 24.88 dB to 30.67 dB. The absorption contribution (SE_A/SE_T) increased from 84.2% to 92.8%, significantly improving the electromagnetic interference shielding and the absorption contribution of the AgNWs in the composites. This was attributed to the backfilling of the porous structure by the AgNWs, which promoted multiple reflections and enhanced the absorption contribution.