Nickel‐Aluminum Hydrotalcite for Improving Flame Retardancy and Smoke Suppression of Intumescent Flame Retardant Polypropylene: Preparation, Synergy, and Mechanism Study

Abstract Intumescent flame retardants (IFR) are widely used in the field of flame retardant polypropylene (PP), but their flame retardant efficiency and smoke suppression properties need to be further improved. Herein, a Ni‐Al LDH (layered double hydroxide) is obtained successfully by coprecipitation and microwave hydrothermal technique and used as a synergist to improve the flame‐retardant and smoke‐suppression properties of triazine‐based IFR. The results showed that IFR/Ni‐Al LDH exhibited the best synergistic effect when the IFR is replaced by 5 wt% Ni‐Al LDH. 17 wt% IFR/Ni‐Al LDH enabled the PP composites to achieve UL‐94 V‐0 rating with a high LOI of 29.8%. Besides, the introduction of Ni‐Al LDH effectively decreased the heat and smoke release of the PP/IFR composites due to its catalytic charring effect. This is mainly attributed that the introduction of metal ions in Ni‐Al LDH effectively improved the strength and crosslinking degree of char layer and promoted the formation of a cohesive and dense char layer. The formed high‐quality char layer effectively exerted the barrier effect in condensed phase. Therefore, the PP/IFR/Ni‐Al LDH composites exhibited excellent flame‐retardant and smoke‐suppression performance. This investigation provided a facile way to prepare environment‐friendly and high‐performance flame retardant PP composites with wide application prospects.