An investigation of the effects of zeolites on the thermal degradation and charring of APP-PER by TGA-XPS

The effects of zeolites 4A, 13X, mordenite, and ZSM-5 on the thermal degradation and charring of intumescent ammonium polyphosphate (APP)-pentaerythritol (PER) systems were explored by X-ray photoelectron. spectroscopy (XPS) and thermal gravimetric analyses (TGA). The weight loss rate of the third main degradation step (corresponding to the maximum degradation rate of APP-PER) was remarkably decreased for all systems with addition of zeolites, especially for the systems with 4A and 13X where the minimal weight loss rate, 0.13%/degreesC and 0.11%/degreesC, were found. The residues of APP-PER systems with 4A and 13X at 600degreesC were 33-35% higher than that of the pure APP-PER system. The XPS-TGA results indicated that zeolites might execute their effects on the thermal degradation of APP-PER by two ways, that is, by catalyzing the esterification reaction between APP and PER at temperatures below 250degreesC and enhancing the cross-linking and charring by SiO2 and Al2O3 produced by the breakage of zeolites at temperatures above 250degreesC. Meanwhile, the thermal degradation and charring processes of the APP-PER systems with zeolites were found to be related to the type of the zeolites.