Phthalonitrile Co‐Resin Blends for Improved Processing and Oxidative Stability

ABSTRACT We explored the tailorability of resin processing behavior, thermal stability, and thermomechanical properties through the formulation of two well‐established phthalonitrile (PN) monomers: the bisphenol A derived PEEK‐based PN resin (BisA‐PEEK‐PN) and a low‐viscosity and highly processable phosphate‐based PN monomer (PPN) with exceptional thermooxidative stability. The resins were melt blended in varying ratios and the results of this research offer a simple method for lowering the processing temperature by 25 to 50°C and melt viscosity from 1 to 0.75 Pa s at 175°C of the blended resin. As more PPN is mixed into the BisA‐PEEK‐PN blend, a 3.7 GPa (238%) increase in the room temperature storage modulus was observed and it was also found to dramatically improve the thermooxidative stability of cured network blends, as indicated by an increase in the char yield (1000°C, air) from 5% to 55%. In addition, a synergistic effect between the oxidatively stable PPN and BisA‐PEEK‐PN in the blend was observed in blended networks which exhibited a maximum char yield of 79% under N 2 , surpassing either of the neat resins.