Abstract:

A series of epoxy composites with different loadings of 1⁃oxo⁃4⁃hydroxymethyl⁃2，6，7⁃trioxa⁃l⁃phosphabicyclo ［2.2.2］ octane （PEPA） and ammonium polyphosphate （APP） and a fixed loading of montmorillonite （MMT） were prepared to enhance their flame⁃retardancy. The synergistic effect of APP and PEPA on the flame⁃retardant properties of the epoxy composites was evaluated by vertical burning experiment， limiting oxygen index， and cone calorimetry. A smoke density test was also carried out to demonstrate the collaborative smoke suppression effect of APP and PEPA. The experimental results indicated that when 15 wt% of APP/PEPA/MMT at a mass ratio 69/25/6 was incorporated into epoxy resin， the resultant epoxy composite obtained an improvement in limiting oxygen index up to 31.5 % and reached the UL94 V⁃0 rating in the vertical burning test. Moreover， its peak heat release rate （HRR） and total smoke release （TSR） decreased by 73.6 % and 70 %， respectively. Based on the HRR， peak HRR， and TSR results obtained from cone calorimetric measurements， PEPA， APP， and their compounds can generate good flame⁃retardant effectiveness in both gas phase and condensed phase. To understand the synergistic mechanisms about the flame⁃retardant and smoke suppression effects deeply， thermal gravimetric analysis coupled with Fourier⁃transform infrared spectroscopy， visual observation， and scanning electron microscopy were conducted to characterize the gas and condensed phases of epoxy composites containing APP and PEPA flame retardants.

Key words: epoxy resin, composite, flame retardancy, ammonium polyphosphate, 1?oxo?4?hydroxymethyl?2，6，7?trioxa?l?phosphabicyclo ［2.2.2］ octane