Green synthesis and application of P/N-containing fire retardants in PA6/aluminum diethylphosphinate composites

Green synthesis and application of P/N-containing fire retardants in PA6/aluminum diethylphosphinate composites

Engineering polyamide 6 (PA6) features excellent mechanical, electrical and chemical properties yet the inherent flammability of pristine PA6 restricts its practical applications regardless of the huge market demand. Therefore, it is imperative to develop PA6 with fire safety. A typical phosphorus-containing fire retardant, aluminum diethylphosphinate (ADP), has shown high fire-retardant efficiency in PA6 and has been the main component of commercial products to apply in various polymers. However, ADP-participated PA6 has several shortcomings: large amounts of heat and smoke released; less sufficient char residue generated; higher production cost due to the expensive ADP. Therefore, it is significant to develop synergistic agents for ADP to inhibit heat release, generate more char residue and lower the price for industrial application concerns. Studies have been conducted on synthesis of new compounds to act as synergists for ADP. Nevertheless, most synthesis approach involves using organic or even toxic reagents as well as specific gas atmosphere, few studies reported superior fire retardancy in multi-fire assessments. Besides, there is a lack of in-depth understanding of the modes of action and the relationship of the prepared synergists and ADP to improve the fire retardancy of PA6 with various additive loadings. For these reasons, this thesis focuses on developing green strategies to synthesize three melamine-based phosphorus and nitrogen-containing compounds (P/N-FRs) in water medium: a P/N-containing supramolecular microplate (MTP), a 2D biobased P/N-containing aggregate (MPA) and a P/N/B-containing aggregate (MBA). Then, the as-synthesized P/N-FRs are applied as synergists of ADP for creating fire-retardant PA6 composites. Upon the specific additive ratios, the fabricated PA6 systems demonstrate desired fire retardancy. The comprehensive properties are investigated and the results show distinctive synergistic effect between the synthesized P/N-FRs and ADP. This work provides a new eco-benign strategy for synthesis and application of P/N-FRs as synergists for ADP and other flame-retardant systems for other polymer matrices.

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