Solvent-Free Synthesis of a Hyperbranched Polyphosphoramide Cocuring Agent and Its Application in Fire-Safe, Mechanically Strong, and Tough Epoxy Resin

Abstract

The synthesis procedures of the majority of hyperbranched flame retardants (FRs) involve numerous toxic organic solvents, resulting in severe environmental and human health hazards. Herein, a hyperbranched polyphosphoramide FR (DMP) was synthesized by a one-pot, catalyst-free, and solventfree strategy, which was utilized as a cocuring agent to fabricate high-performance epoxy resin (EP) composites with excellent fire safety performance, enhanced mechanical strength, and toughness. EP with a loading of 8 wt % of DMP (EP/8DMP) exhibited a UL-94 V-0 rating and a limiting oxygen index of 28.0%. Meanwhile, DMP endowed EP/8DMP with 51.9, 53.4, and 57.6% reductions in total heat release, total smoke production, and total CO production, respectively, compared with those of unmodified EP at a phosphorus content of only 1.12 wt %. The flame-retardant mechanism of DMP in EP composites was attributed to flame inhibition in the gas phase and charring performance in the condensed phase. Additionally, both the flexural property and impact strength of EP/DMP composites were well-preserved. Therefore, this work presents a green and economic approach for developing a highly efficient hyperbranched FR for the fabrication of fire-safe, mechanically strong, and tough EP composites.

Hierarchical Nanospheres toward Flame-Retardant, Mechanically Strong, and Low-Toxicity Epoxy Resins

“…Thermogravimetric analysis coupled with Fourier transform infrared spectroscopy (TG-FTIR) is applied to examine the gas-phase products engendered during the degradation process of EP and EP/SCP composites, providing valuable insights into the composition and characteristics of the volatile compounds . As demonstrated in the three-dimensional TG-FTIR images (Figure a,b), the volatile products that were given off during the decomposition of EP and EP/SCP revealed a comparable constituent.…”