Recyclable flame retardant phosphonated epoxy based thermosets enabled via a reactive approach

The development of reusable fire-safe polymers with a prolonged lifetime heralds the switch for transition towards circular economy. In this framework, we report novel phosphonated thermoset which is composed networked phosphonate esters containing both PC and PO bonds. Employing simple one-pot, two-step synthetic methodology, oxirane groups epoxy resin were partially reacted various amounts reactive bis H-phosphonate monomer, cured cycloaliphatic hardener to obtain multifunctional thermosets up 8% phosphorus (P) content. Though 2.5% P was adequate achieve good flame retardancy, concentration > 5% necessary accomplishing material reprocessability recyclability. These exhibited high Tg (94 °C – 140 °C) thermal stability. Fire performance via cone calorimetry showed effective reduction in peak heat release rate (pHRR, 75%) significant inhibition total smoke production (TSP, 72.5%), attributed gas condense phase actions moieties. This explored as transparent coating on wood where an intumescent retardant mechanism observed. higher content (6%) demonstrated excellent damage reparability thermomechanical driven by transesterification induced network rearrangement. used manufacturing flax fiber reinforced composite, demonstrate its future application polymer matrix composite materials.