Synthesis of a 9,10-dihydro-9-oxo-10phosphaphenanthrene-10-oxide-based reactive flame-retardant curing agent

Abstract

This paper aims to prepare a new curing agent, reactive flame retardant (DTF), through one-pot synthesis of 9,10-Dihydro-9-oxo-10-phosphaphenanthrene-10-oxide (DOPO), formaldehyde and triacetonediamine for Epoxy resin (EP). This new DTF was successful prepared through Fourier-transform infrared, 1H NMR, and 31P NMR spectroscopy. The flame-retardant epoxy thermoset was prepared using the 4′4-diaminodiphenylmethane (DDM) as a co-curing agent. The analysis results using the differential scanning calorimetry (DSC) showed that DTF can cure EP and improve the carbon residue yield of epoxy thermoset after burning. It observed that if the content of phosphorus was 1.0 wt%, the limiting oxygen index (LOI) of EP/DDM/DPT-4 was 30.4%, and UL94 reached the V-0 rating. The highest tensile property of the epoxy thermoset reached 98.56 MPa (P content = 0.5%), whereas the highest flexural property reached 137.28 MPa (P content = 0.75%), and the highest impact property reached 24.1 KJ · m–2 (P content = 0.5%).