A Phosphorus and Nitrogen Containing Halloysite Derivative as Multifunctional Flame Retardant for Biobased Polyamide 56

Herein, a biobased polyamide (PA56) is selected as the polymer matrix and halloysite nanotubes (HNTs) are chosen as the reinforcement material. By using a sustainable synthesis pathway, a biobased flame retardant (FR) complex formed by phytic acid (PhA) and chitosan is successfully grafted to the HNTs. The structure of the modified HNTs is characterized by Fourier transform infrared spectroscopy, the morphology and dimensions are studied using transmission electron microscopy and scanning electron microscopy with energy dispersive X‐ray. After the introduction of 3 wt% HNTs into the PA56 the thermogravimetric analysis onset temperatures and residue are notably increased. The modified nanomaterials also provide higher tensile strength and elongation at break. Furthermore, the biobased FR exhibited a synergistic effect on fire performance. The peak heat release rate is decreased by 51% and the combustion times are delayed for more than 100 s. The significant increase in flame retardancy is attributed to the barrier effect of HNTs and the catalytic carbonization induced by PhA during the formation of the char layer. The results of this study show that it is possible to enhance the flame retardant and mechanical properties of polyamide composites by using the combination of nanoclay and biobased flame retardant additives.