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A novel nano-clay flame retardant (HNTs@MEL-PA) is prepared by modifying halloysite nanotubes (HNTs) with supramolecular self-assembly technology using melamine (MEL) and bio-based phytic acid (PA) as the building blocks. Transmission electron microscopy images and Fourier transform infrared spectra show that the surface of HNTs is successfully decorated with MEL-PA supramolecular aggregates by hydrogen bonding. The feasibility of using HNTs@MEL-PA as a flame retardant for polypropylene (PP) is explored. Compared with PP/HNTs composites, the dispersion of HNTs@MEL-PA and its interfacial interactions with PP matrix are greatly improved. Heat release of PP is decreased in a certain degree and its smoke release is greatly reduced by HNTs@MEL-PA. With the addition of 15 wt% HNTs@MEL-PA, total smoke production of PP is decreased from 15.7 to 10.2 m2, indicating the greatly improved fire safety. Flame retardant and smoke suppression mechanisms of HNTs@MEL-PA are proposed based on thermal decomposition results and the analysis on char residue. Image 1 • HNTs were modified by supramolecular self-assembly technology. • Combustion behaviors of PP/HNTs@MEL-PA composites were investigated. • Flame retardant and smoke suppression mechanisms of HNTs@MEL-PA were concluded. [ABSTRACT FROM AUTHOR]

Organically modified ammonium polyphosphate (APP) flame retardant is prepared by supramolecular assembly method using melamine formaldehyde (MF) resin and phytic acid (PA) as building blocks. Surface characteristics of APP are modified, resulting in the enhancements in water resistance, dispersion in the polymer matrix and their compatibility. This supramolecular assembly modified APP (APP@MF-PA) matches well with charring-foaming agent (CFA) to achieve excellent fire safety for polypropylene (PP), and the superiority over conventional APP is observed. Heat, CO and CO 2 releases of PP are greatly decreased by the intumescent flame retardant (IFR) formulation containing APP@MF-PA and CFA. The modification of APP with MF-PA supramolecules are beneficial to improve the yield, insulation properties, graphitization degree and compactness of char. Flame-retardant mechanisms are demonstrated according to the investigations on gaseous and condensed phase products. This novel and facile modification method provides a new strategy for improving the flame-retardant efficiency of IFR. Image 1 • The surface characteristics of APP were modified by supramolecular assembly. • Fire hazards of PP were greatly reduced by this modified APP and CFA. • Flame retardant mechanisms were proposed. [ABSTRACT FROM AUTHOR]

• A novel bio-based flame retardant was synthesized via a simple ionic reaction. • The synergistic effects of IFR on combustion behaviors of PLA were explored. • APP/ATMP-NA-Fe endowed PLA with excellent flame-retardant performance. The high flammability and severe melt-dripping during the combustion are the most marked fire hazards for polyesters, such as polylactic acid (PLA). In this work, a bio-based flame retardant (ATMP-NA-Fe) was successfully synthesized by a simple aqueous ionic reaction by using amino trimethylene phosphonic acid (ATMP), nicotinamide (NA) and FeCl 3 •6H 2 O as raw materials. The ATMP-NA-Fe and ammonium polyphosphate (APP) have good synergistic effects on improving the flame-retardant performance and retarding the combustion melt-dripping of PLA. With a 10 wt% total loading of ATMP-NA-Fe and APP (1:1), the limiting oxygen index value of corresponding PLA composite (PLA3) increases from 20.1% to 32.8%, and it passes UL-94 V-0 rating without melt dripping. The cone calorimetry results show that compared with pure PLA, the peak heat release rate, total heat release and average mass loss rate of PLA3 are reduced by 66.4%, 14.9% and 76.7%, respectively. Via the analysis on the condensed and gas phase products, the flame-retardant mechanism of PLA/APP/ATMP-NA-Fe composites is proposed. This work provides a new approach for improving flame-retardant performance of PLA and promoting the utilization of renewable resource. [ABSTRACT FROM AUTHOR]