Investigation of Chemorheology and Curing Kinetics of Cyanate Ester/Epoxy Blends with A Reactive Flame Retardant using Differential Scanning Calorimetry and Rheological Measurements

Cyanate ester (CE) and epoxy (EP) resin blends are widely used in aerospace, automotive, and electronics due to their thermal stability, mechanical toughness, and cost-effectiveness. However, incorporating flame retardants like poly(m-phenylene methylphosphonate) (PMP) alters curing kinetics and rheology. This study examines the impact of 3 wt% PMP on CE/EP blends to optimize processing for autoclave curing. Differential scanning calorimetry (DSC) and rheometer reveal a PMP-induced dual-stage curing mechanism, with activation energies of 80 kJ/mol and 115 kJ/mol for initial and final stages, respectively. PMP accelerates curing, reducing gelation times by over 90% from 324 minutes to 25 minutes at 150°C. Viscosity analysis identifies a critical low-viscosity plateau (100°C–190°C), facilitating flowability for autoclave, oven, or RTM curing. At 110°C, PMP-modified blends maintain a viscosity below 2000 cP, ensuring effective impregnation. These findings guide composite manufacturing, highlighting the need for pre-heating to improve mold impregnation and final composite quality. PMP serves as a multifunctional additive, enhancing flame retardancy, accelerating curing, and improving processability, supporting the development of high-performance, cost-effective materials for advanced industrial applications.