Synergistic Effect between a Novel Hyperbranched Flame Retardant and Melamine Pyrophosphate on the Char Forming of Polyamide 6

A novel hyperbranched polyphosphate bisphenol-S ester (HPPES) flame retardant was prepared. The structure and thermal stability of the product were characterized. Polyamide 6 (PA6), HPPES and melamine pyrophosphate (MPP) were used to prepare flame retardant PA6 (FR-PA6) through melt blending. Limiting oxygen index (LOI), UL-94 vertical burning methods, thermogravimetric analysis (TGA), X-ray photoelectron spectroscope (XPS) and scanning electron microscope (SEM) were used to investigate the combustion properties, thermal degradation behaviours and char forming of FR-PA6. The results showed that synergistic effect between HPPES and MPP was present, which enhanced the char forming and flame retardance of PA6.