Locally π-π conjugated polyimide cured triglycidyl isocyanurate epoxy resin with enhanced dielectric polarization and microwave absorption performance for X and Ku bands

Creatively, endowing the resin matrix with microwave absorption performance is an effective strategy to improve the comprehensive performance for microwave absorption materials and eliminate the contradiction between matrix and absorbent. Herein, a high polar epoxy resin that triglycidyl isocyanurate (TGIC) is chemically cross-linked with locally π-π conjugated polyimides (PI) to create a novel absorbing resin matrix designed for special responses in X and Ku bands. By comparing the dielectric properties and microwave absorption performance of PBI-D/TGIC (containing benzene), PNI-D/TGIC (containing naphthalene) and PPI-D/TGIC (containing perylene), their dielectric polarization loss and microwave absorption responses will be enhanced with the increase of conjugated benzene number, which is ascribed to the enhanced π-π conjugated polarization and the instantaneously reduced resistance stimulated by electromagnetic waves (EMWs). Simultaneously, the addition of an appropriate amount of PPI-D significantly enhances the microwave absorption performance, mechanical strength, and thermal stability of TGIC-based resins. When the mixing mass ratio of PPI-D to TGIC is 1:4, the obtained PPI-D/TGIC-0.5 (PPI-D: 25.23 wt%) possesses the best minimum reflection loss (RLmin) as −15.6 dB (16.4 GHz, 3.0 mm) and −8.6 dB (8.2 GHz, 4.0 mm), which is three times higher than the RLmin of TGIC. Especially, the effective absorption bandwidth (EAB < -10 dB) of PPI-D/TGIC-0.5 resin can reach up to 3.44 GHz (6.0 mm) and 2.88 GHz (3.0 mm), breaking the limitations of conventional resins. Additionally, PPI-D/TGIC-0.5 resin exhibits excellent compression performance (37 MPa), elastic modulus (1065.4 MPa) and thermal stability (T10wt.%=295 ℃). PPI-D/TGIC-0.5 resin is a strong candidate for the ideal absorbing resin matrix and holds significant potential in the applications for microwave absorption materials.