Study on the Curing Behaviors of Benzoxazine Nitrile-Based Resin Featuring Fluorene Structures and the Excellent Properties of Their Glass Fiber-Reinforced Laminates.

Benzoxazine and o-phthalonitrile resin are two of the most eminent polymer matrices within high-performance fiber-reinforced resin-based composite materials. Studying the influence modalities of their structures and forming processes on performance can furnish a theoretical basis for the design and manufacturing of superior performance composite materials. In this study, we initially incorporated a fluorene structure into the molecular main chain through molecular design to prepare a fluorene-containing benzoxazine nitrile-based resin. The polymerization reaction behavior and process of this resin were monitored meticulously using differential scanning calorimetry and infrared spectroscopy. Meanwhile, by manipulating the pre-polymerization reaction conditions, the impact of the pre-polymerization reaction on the polymerization behavior of the resin monomer was investigated, respectively. Subsequently, diverse glass fiber-reinforced resin-based composite materials were fabricated via hot-pressing in combination with a programmed temperature rise process. Through the characterization of structural strength and thermomechanical properties, it was found that the composite laminates all manifested outstanding bending strength (~600 MPa) and modulus (>30 GPa). Nevertheless, with the elevation of the post-curing temperature, the structural strength and modulus of the composite materials displayed distinct variation laws. This study also discussed the variation laws of the thermal properties of the composite materials by analyzing the glass transition temperature and crosslinking density. Additionally, the interface bonding effect between the glass fiber and the resin matrix was deliberated through the analysis of the cross-sectional morphology of the composite laminates. The results demonstrated that this work proposes an improved matrix resin system with outstanding thermal stability and mechanical properties that broadens the foundation and ideas for subsequent research.