High-Performance Wood–Plastic Composites Based on Self-Assembly Sandwich-Like 2D/2D MMT/Zn²⁺-MEL-PA Supramolecular Structure: Enhanced Mechanical and Flame-Retardant Properties

In this work, an environmentally friendly multicomponent flame retardant denoted as a sandwich-like 2D/2D montmorillonite/Zn2+-MEL-PA (MMT/ZnMPA) plate was successfully synthesized through a "bottom-up" supramolecular self-assembly method, in which the ultrathin ZnMPA nanosheets were lying parallell on both sides of MMT plates. Then, the MMT/ZnMPA plate served as an excellent performance nanofiller in wood flour/polypropylene (WF/PP) composites. Microstructure characterization indicated that the MMT/ZnMPA plate had the uniform dispersion in the WF/PP composites with excellent interfacial compatibility, thereby simultaneously improving mechanical properties and flame retardancy of WF/PP composites. With the incorporation of 20 wt % MMT/ZnMPA plates, the peak heat release rate and total heat release rate were remarkably decreased by 28.1% and 17.8% in contrast to WF/PP composites. Moreover, the tensile strength and flexural strength were increased by 20.6% and 15.2% compared to WF/PP composites, respectively. This work has presented a facile tactic for integrating phosphorus and nitrogen-containing flame retardant with MMT plates to develop WF/PP composites with high mechanical and flame-retardant properties.