A quantitative coupling pyrolysis mechanism modeling of flame-retardant composites and their bubbling, breaking, charring behaviors

The coupling pyrolysis behavior and mechanism of composites with multi-components are important for the formula optimization of future flame-retardant (FR) materials. Series of thermogravimetry (TG) experiments are carried out for five FR-composites with different ratios of aluminum hydroxide (ATH)/magnesium hydroxide (MDH) additives, as well as some binary material samples in N2 and air atmospheres, respectively. A method is developed to quantitatively evaluate the different pyrolysis of real flame-retardant samples through the comparison with the corresponding mass-weighted curves of each component. It indicates that the real DTG curves of FR-composites are narrowed with larger peaks and shift towards higher temperatures always about 30 degrees C than the calculated ones during their pyrolysis at 250-350 degrees C. The results of binary systems(EVA+MDH, MDH+MCA) indicate the enhancing of acid on the early reaction of MDH at 350-450 degrees C. In addition, the DTG in higher temperatures are not as large as the calculated ones in air atmosphere, especially for the FR-composites with smaller ATH/MDH ratio. Finally, the morphology evolution of samples also suggests that the bubbling, breaking and charring behaviors play an important role in their coupling pyrolysis mechanism in different temperature ranges. This is a new method for investigating the pyrolysis mechanism of FR-composites through quantitatively analyzing the DTG data and real-time morphology monitoring, which deepens the understanding of their complicated chemical and physical reactions when heated.