Abstract
The preparation of lightweight materials with electromagnetic interference-shielding effectiveness higher than 30 dB is critical for most industrial and consumer applications. Compounding polymer resin with conductive filler can generate excellent electromagnetic interference-shielding effectiveness but usually leads to a high-sample density, while the foaming of polymer composite suffers from the significant-reduced electromagnetic interference-shielding effectiveness. In this study, polyetherimide composite foams with loading of 10–80 phr (parts per hundred of resins) nickel particles were fabricated to meet the gap. The polyetherimide/nickel composite foams possessed uniform cell structure and low-sample density such as 0.86 g/cm3 at 70 phr nickel. The coupling effects of gravity settlement and cell-structure solidification led to the formation of gradient distribution of nickel particles across the foams. The formed novel structure facilitated the enhancement of multi-reflection and multi-scattering among nickel particles and cells. As a consequence, polyetherimide/nickel foam with 70 phr nickel (PEIN70) possessed a high-electromagnetic interference shielding effectiveness of 86.7–106.5 dB over a frequency range of 50–3000 MHz. When the sample density was considered, the specific electromagnetic interference shielding effectiveness of PEIN70 foam was as high as 121.3 dB/(g/cm3) at 1 GHz, which was higher than the reported electromagnetic interference-shielding materials. The excellent electromagnetic interference-shielding properties, lightweight, well-defined resin properties ensure polyetherimide/nickel composite foams useful in many advanced applications.
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