The
novel polybasic carboxylic acid (HCPVC) consisting of vanillin
and hexachlorocyclotriphosphazene was synthesized successfully by
the nucleophilic substitution reaction and the Pinnick oxidation.
Fourier transform infrared spectroscopy (FTIR) and 1H nuclear
magnetic resonance (1H NMR) were used to identify its chemical
structure. HCPVC was used as a curing agent to employ in wood epoxy
coating. The optimum curing condition of epoxy resin (DY-E44) with
HCPVC and its apparent activation energy were determined by differential
scanning calorimetry (DSC), and the results showed that it was suitable
for utilizing in wood. After stepwise curing, the epoxy coatings cured
with HCPVC presented excellent hardness, adhesion, water resistance,
and solvent resistance. Meanwhile, HCPVC-EP exhibited the high char
yield of 37.1% at 700 °C, as well as prominent flame retardancy
with UL-94 V-0 rating and the higher LOI value of 30.7%, which are
much higher than the common epoxy coatings and uncoated splines. Besides,
the flame-retardant mechanisms of HCPVC-EP were investigated by scanning
electron microscopy (SEM) after the UL-94 tests, and the consequence
demonstrated that the formation of intumescent dense char layer restrained
the further combustion and pyrolysis in the condensed phase. Meanwhile,
the conclusion of thermogravimetric analysis/infrared spectrometry
(TGA-FTIR) affirmed that HCPVC-EP released more inert gases during
heating and suppressed in-depth decomposition in the gaseous phase.
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