Cyanate Ester Resin with High heat‐resistance and Degradable Diacetal Structure: Synthesis, Polymerization and Properties

Cyanate resins are high-performance thermosetting resins with excellent mechanical, thermal, and dielectric properties. In this work, a novel cyanate ester monomer, 3,9-bis-(4-cyanato-phenyl)-2,4,8,10-tetraoxa-spiro[5.5]undecane structure (DBCE), is prepared based on a diphenol (DB) with a degradable diacetal structure. The characterization of the chemical structures and polymerization behaviors of the samples are achieved by nuclear magnetic resonance spectroscopy, fourier transform infrared spectroscopy, and differential scanning calorimetry. The obtained results confirm the successful syntheses of DB and DBCE, and the polymerization temperature of DBCE is between 160 degrees C to 250 degrees C, which is lower than that of a comparative commercial cyanate ester resin (BADCy). The thermal and dielectric properties of the curedresin (Poly-DBCE) are explored by dynamic mechanical analysis, thermogravimetric analysis, and an Agilent impedance analyzer. The results reveal that Poly-DBCE manifest promising heat resistance (T-g = 294 degrees C) and thermal stability (T-d,T-5 = 347 degrees C and char yield at 800 degrees C = 37.6%). The dielectric constant and dielectric loss of the Poly-DBCE at 10 MHz are 3.11 and 0.0095, respectively. Additionally, the Poly-DBCE is completely degraded under mildly acidic conditions, and efficient recoveries of carbon fiber and glass fiber with high values are reported from their corresponding fiber-reinforced composites.