Fluorinated polyetherimide as the modifier for synergistically enhancing the mechanical, thermal and dielectric properties of bismaleimide resin and its composites

The aviation industry has a substantial demand for bismaleimide (BMI) resins that possess high toughness, excellent thermal stability, and low dielectric constant, which are critical for wave-transparent materials. This study presents the synthesis of a novel fluorinated polyetherimide (F-PEI) and its integration with BMI resin using an in situ pre-polymerization method. Upon blending 4 wt% F-PEI with bismaleimide resin, the resulting blending resin (BDP-4) demonstrated a significant enhancement in both impact strength (59.6% increase) and flexural strength (13.9% increase) compared to the unmodified BMI. Additionally, the glass transition temperature of BDP-4 was enhanced to 299.3°C, representing a 5°C increase, and the corresponding dielectric constant (k) and dielectric loss (tan δ) at 15.2 GHz were decreased from 3.02 to 2.96 and from 0.010 to 0.009, respectively. These improvements are attributed to the phase separation induced by the F-PEI content, which engendered a synergistic toughening mechanism beneficial for both thermal and dielectric attributes. Notably, the flexural strength (630.1 MPa), flexural modulus (26.5 GPa), and interlaminar shear strength (67.1 MPa) of quartz fiber reinforced F-PEI/BMI composites (QF/BDP-4) exceeded those of pure BMI composites. The findings indicate that F-PEI modification is an effective strategy for advancing BMI resin performance, with potential applications in high-performance industries such as aerospace and electronics.