Preparation and properties of high strength and high modulus polyimide fiber/modified cyanate resin composites

The bisphenol A cyanate ester(BCE) was modified by 4,5-epoxyhexane-1,2-dicarboxylic acid diglycidyl ester(TDE-85), phenyl glycidyl ether(PGE) and nonylphenol (NP) (TPNCE), and high strength and high modulus polyimide fiber/TPNCE(PI/TPNCE) composites were prepared by wet winding and autoclave molding process. The mechanical properties and dielectric properties of TPNCE resin and PI/TPNCE composites were analyzed. The results show that the impact strength of TPNCE resin reaches 14.2 kJ/m², which is nearly double that of the BCE. Compared with the unmodified system, the TPNCE resin keep excellent dielectric properties, the curing temperature drops by about 43℃, and the interface is better with PI fiber. In addition, the PI/TPNCE composite has 0°tensile strength of 1485 MPa, bending strength of 758 MPa, compressive strength of 322 MPa, dielectric constant of about 3.15 and dielectric loss factor of 0.005-0.0075 at 7-18 GHz. The glass transition temperature of PI/TPNCE composite is 197℃ and density is 1.28 g/cm³. This study realizes an important breakthrough in the combination of high-strength and high-modulus PI fiber and cyanate ester, and provides a new idea for the design and material selection of lightweight high-strength structural-functional integrated composites.