Synthesis of a Novel Spiro Phosphorus–Nitrogen Concerted Reactive Flame-Retardant Curing Agent and Its Application in Epoxy Resin

Abstract

Spiro-phosphorus (P)-based reactive flame retardant (SPDPT), a novel reactive flame-retardant epoxy resin (EP) curing agent, was prepared through the one-pot synthesis of triacetonediamine, pentaerythritol, and P oxychloride. The successful preparation of SPDPT was confirmed through Fourier-transform infrared (FTIR) spectroscopy, 1H NMR spectroscopy, 31P NMR spectroscopy, and elemental analysis. The flame-retardant epoxy thermoset [e.g., EP/4′4-diaminodiphenyl sulfone (DDS)/SPDPT] was prepared by using DDS as the co-curing agent. Differential scanning calorimetry (DSC) results show that SPDPT can cure EP. Thermogravimetric analysis (TGA) results show that improve the carbon residue yield of the epoxy thermoset after burning. When the P content was 1.0 wt%, the limiting oxygen index value of the EP/DDS/SPDPT-4 sample was 26.4%, and UL94 reached the V-0 rating. The tensile property of the epoxy thermoset reached 37.20 MPa, the flexural property reached 63.82 MPa, and the impact property reached 21.57 KJ⋅m–2.