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.

Recent advances in metal-family flame retardants: a review

“…Jiang et al successfully obtained Ni–Al LDH and used it as synergist to improve triazine-based IFR's flame retardancy and smoke suppression properties. 29 The flame-retardant mechanism is shown in Fig. 2 .…”

“…27,28 This increases ameresistance of the polymer, and they can also reduce emission of smoke and hazardous gases during polymer burning. [29][30][31] The earliest metal-based ame retardants developed were metal hydroxides, most commonly aluminum trihydroxide (ATH) 32,33 and magnesium hydroxide (MH). [34][35][36] Jiao et al added MH to ethylene vinyl acetate (EVA) as a ame retardant to improve its re and smoke suppression capabilities.…”

Surface-Modified LDH Nanosheets with High Dispersibility in Oil for Friction and Wear Reduction

“…Layered double hydroxides (LDHs) are typical 2D materials with a graphite-like layered structure that can easily slip between layers. Their chemical formula is [M 2+ 1– x M 3+ x (OH) 2 ] x + (A n – ) x / n · m H 2 O, where M 2+ and M 3+ are interlayer metal cations and A n – is an interlayer anion. − Based on the ability to modulate metal cations, molar ratios, and interlayer anions, LDH nanosheets have a wide range of applications in catalysts, , ion-exchange hosts, biology, , flame-retardant additives, , and sensor applications. Besides, the LDH manufacturing process is relatively easy to amplify, resulting in significant material and production cost reductions .…”

Synergistic effects of fly ash on thermal, combustion, and mechanical properties of polypropylene including intumescent flame retardant

“…[38][39][40] Some fillers such as zinc borate, montmorillonite, expanded graphite, sepiolite, clay, calcium carbonate, nickel-aluminum hydrotalcite, boric acid, mica, and strontium carbonate have been used to reinforce the char layer formed by IFR system, thereby enhancing the thermal/fire resistances of the composites and smoke suppression. [41][42][43][44][45][46][47][48][49][50] Furthermore, some improvements in mechanical properties were also reported with the addition of the fillers. Importantly, the incorporation of these fillers reduces the production costs of the composites by replacing the more expensive IFR systems and PP.…”