Polybenzoxazine modified by phenolphthalein-based poly(arylene ether nitrile): Better thermal, mechanical, and dielectric properties

Polybenzoxazine, as a ring-opening polymerized thermosetting resin, suffers from poor toughness. Blending with thermoplastic polymers is a convenient and efficient approach to improve the toughness, however, at the cost of thermal and mechanical properties. In this work, a high-performance thermoplastic polymer poly(arylene ether nitrile) (PEN) with T-g higher than polybenzoxazine's was used to modify the polybenzoxazine poly(BA-a). It was found that the PEN improved the mechanical properties, with elongation at break value increased from 1.75% to 3.11% and tensile strength increased from 17.99 to 32.19 MPa when 30 wt% of PEN was introduced. Moreover, due to the better thermal resistance and thermal stability of PEN, T-g of the composites increased from 205.6 to 220.5 degrees C, chary yield at 800 degrees C (Y-c) increased from 28% to 46.4%. It was also noted that homogeneous blend was formed at low loading of PEN but phase separation occurred at high content of PEN, with PEN forming isolated spheres. Due to the voids formed between continuous phase and the isolated PEN spheres, the dielectric constant decreased from 3.84 to 3.30 at 1 MHz.