Simultaneous enhancement of thermal and dielectric properties of phthalonitrile resin via an organic-inorganic hybrid approach

Abstract

The usage of high-performance phthalonitrile (PN) resin has become increasingly common in the aerospace fields. However, achieving the balance between low dielectric under high frequency and high thermal stability remains a challenge. This study presented an organic-inorganic hybrid method to improve synchronously the thermal and dielectric properties of the resin, via the covalent bond to uniformly disperse epoxy polyhedral oligomeric silsesquioxanes (EP-POSS) into PN resin. The results indicate that EP-POSS significantly affect the curing mechanism of PN resin, and the main structure of cross-linking network changes from triazine to low polarity and more stable phthalocyanine. Compared to pure PN resin, the dielectric constant and dielectric loss at 10.5 GHz of the sample containing 1 wt% EP-POSS reduced from 3.55 and 0.013 to 3.37 and 0.006. Furthermore, POSS-containing polymers presented superior thermal and thermal oxidation stability with T_d5% of 564–567 °C and T_g above 500 °C. The formed SiO₂ layer on the resin surface during the high-temperature sintering protected the structural integrity effectively. This study provides novel insights into the development and application of PN resin in extreme environments.