Advanced phthalonitrile resin systems for vacuum processing

Abstract

Advanced phthalonitrile resin systems based on recently introduced low-melting phosphorus-containing 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 post-curing 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.