Properties and mechanisms of different guanidine flame retardant wood pulp paper

In the present paper, two different guanidine salt flame retardants including guanidine phosphate (GP) and guanidine sulfamate (GS) were employed to flame-retard wood pulp paper (WPP), respectively. Both vertical flame test and microscale combustion calorimetric (MCC) analysis showed that GP-WPP exhibited much higher flame retardant efficiency as compared to GS-WPP. Their different mechanisms were investigated through thermogravimetric analysis (TGA), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). It was concluded that the volatilization of the acid anhydride of GS in high temperature range weakened the catalytic charring effect. In contrast, involatile phosphides decomposed by GP could sustainably increase the acidity of the system, and meanwhile react with some N-containing intermediate decomposition products from the guanidine to produce stable N-P compounds. Hence, it can more effectively promote the formation of the char layer as well as the flame retardant efficiency.