An Investigation of the Effects of Zeolites on the Thermal Degradation and Charring of APP–PER by TGA–XPS

Abstract

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%/ C and 0.11%/ C, were found. The residues of APP–PER systems with 4A and 13X at 600 C 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 250 C and enhancing the cross-linking and charring by SiO2 and Al2O3 produced by the breakage of zeolites at temperatures above 250 C. 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.