Catalyzing charring effect of solid acid boron phosphate on dipentaerythritol during the thermal degradation and combustion

The aim of this study was to investigate the acid catalysis of boron phosphate (BP) to model compound dipentaerythritol (DPER) which acted as char source during the thermal degradation and combustion. Various amounts of BP were added in DPER and then the thermal degradation and combustion behaviors were studied by means of thermogravimetric analysis (TGA) and microscale combustion calorimeter (MCC). Evolved Gases were evaluated using TGA-FTIR; solid residues were fully characterized by FTIR, X-ray photoelectron spectroscopy (XPS), Raman analysis and scanning electron microscopy (SEM). The results of TGA and MCC showed that the addition of BP leaded to the earlier thermal degradation of DPER and increased the amount of char residues, significantly decreased the peak heat release rate of DPER; the results of TGA-FTIR, XPS, Raman analysis and SEM revealed that the presence of BP accelerated the dehydration of DPER, kept more carbon and oxygen elements in condensed phases, promoted the formation of compact and stable char layer. This study indicated that Lewis acidic and Brønsted acidic sites in BP altered the single degradation pathway and catalyzed the crosslinking and char forming of DPER. BP maybe as a potential acid source applied in intumescent flame retardant polymers in future.