Facile synthesis of a novel hyperbranched poly(urethane-phosphine oxide) as an effective modifier for epoxy resin

In this work, a novel hyperbranched poly (urethane-phosphine oxide) (HPUPO) was facilely synthesized from 4,4′-diphenylmethane diisocyanate and trihydroxymethylphosphine oxide at room temperature. When HPUPO was incorporated, flame retardancy and toughness of epoxy resin are improved with maintained T_g and increased modulus and strength. The gas and condensed phase flame retardant mechanisms and toughening mechanisms are provided. The poor compatibility of epoxy resin/HPUPO hybrids determines the unchanged T_g of epoxy matrix phase. The tensile modulus and strength and storage modulus of modified epoxy thermosets are raised due to more rigid skeleton of HPUPO and hydrogen bond interaction. Moreover, the reactivity of epoxy resin curing systems containing HPUPO is elevated for the catalytic effect of its hydroxyl. The surface hydrophilicity of epoxy resin composites is decreased resulting from their increased surface roughness and the hydrophobicity of HPUPO. And the thermal decomposition temperature of epoxy resin hybrids is depressed. The epoxy resins modified by HPUPO with simple synthesis and preparation can be used for various high-performance applications in industries.