Group aggregation effect of polyphenolic phosphaphenanthrene macromolecule on enhancing fire safety and toughness of epoxy thermoset

Polyphenolic phosphaphenanthrene macromolecule (PDBA) was synthesized from 2,2’-di(phosphaphenanthrene-propyl)-bisphenol A (DDBA), via phenol-formaldehyde condensation. With molecular-scale group aggregation feature, PDBA macromolecule exhibits obviously higher efficiency than its starting monomer DDBA in improving the anti-impact, anti-ignition, and self-extinguishing performance of epoxy thermoset (EP). 3%PDBA/EP exhibited a 77.2% higher impact strength than that of neat EP, passed UL94 V-0 rating with a limited oxygen index of 32.8%, and achieved 25.3% lower peak of heat release rate, 16.0% lower fire growth index, and 18.6% higher fire performance index, compared with neat EP. PDBA macromolecule also performs better in reducing thermal-decomposition mass loss rate, improving char residue quality, inhibiting combustion intensity, and maintaining anti-heat deformation performance of epoxy thermoset, compared with equivalent-addition DDBA monomer. With aggregated phosphaphenanthrene and phenolic groups, PDBA macromolecule not only impels epoxy thermoset to undergo toughness fracture with larger quantity of impact energy consumption, but also promotes burning thermoset forming more dense and intact charring residue with better barrier effect. Polyphenolic phosphaphenanthrene macromolecule with group aggregation feature exhibits its superiority in manufacturing advanced fire safety polymer materials with superior comprehensive performance.