Composite number

Engineering

Char

Thermogravimetric analysis

Curing (chemistry)

Epoxy

Pyrolysis

Materials science

Chemical engineering

Thermodynamics

Physics

Limiting oxygen index

Dielectric

Thermal

X-ray photoelectron spectroscopy

Composite material

Fourier transform infrared spectroscopy

Fire retardant

Thermal stability

Optoelectronics

Chemical Engineering Journal

To obtain a latent curing epoxy system with satisfactory thermal stability, flame retardance and dielectric properties, imidazolium dibenzo[c,e][1,2]oxaphosphate (IDOP) was synthesized by a facile way and utilized as a latent flame-retardant curing agent for epoxy resins (EP). It was confirmed that IDOP/EP one-pack system kept reactive inert near room temperature and cured efficiently under heating with a moderate heat release. The curing procedure was explored by X-ray photoelectron spectroscopy (XPS), confirming that the flame-retardant group was incorporated into epoxy chains by covalent and/or ionic bonds, hence the intrinsic flame retardance and excellent thermal stability were given to the cured resins finally. With only 15 wt% IDOP additions, the limiting oxygen index (LOI) increased to 37.0% from 20.5% of the reference sample, and UL-94 V-0 rating was achieved. The results of cone calorimetry test further certified that IDOP/EP showed satisfactory flame retardance dominating in gaseous phase, which was confirmed by the results of thermogravimetric analysis/infrared spectrometry (TG-IR). The thermal mechanical behavior of IDOP/EP was also evaluated by dynamic mechanical analysis (DMA). Especially, the incorporation of the flame-retardant group didn't deteriorate the dielectric properties of the cured resin. Benefiting from the advances, the latent curing epoxy system with excellent comprehensive performance exhibited potential for versatile applications.

Latent curing epoxy system with excellent thermal stability, flame retardance and dielectric property