Advanced Phthalonitrile Resin Systems for Vacuum Processing

Abstract

Advanced phthalonitrile resin systems based on recently introduced low-melting phosphoruscontaining monomers were developed. A new class of bis-benzonitirle reactive plastisizers allowed to obtain resin systems possessing improved processability (melt viscosity < 100 mPa•s at temperatures down to 120 °C) suitable for manufacturing composites by vacuum infusion molding process or RTM at the lowest reported processing temperature of 120 °C on carbon fabric (3K HTA40, twill). The curing cycle was adjusted to achieve the best mechanical properties of the composites reaching 852 MPa in compressive strength. The influence of postcuring conditions on the resulting composites properties was established. After post-curing at 375 °C the obtained composites demonstrated up to 90% mechanical properties retention at 400 °C (τ12 = 60-80 MPa). Solvent-free phthalonitrile prepregs were developed for the first time. Prepreg consolidation yielded high-quality composites. Flame retardant properties of investigated composites demonstrated extremely high LOI > 80%. Thus easy-processable phthalonitriles for out-of-autoclave manufacturing techniques with convenient curing conditions and excellent heat resistant and flame-retardant properties were developed.