A Review of the Application Research on Inorganic Clay Minerals Synergising with Bio-Based Flame-Retardant Systems to...

In recent years, synergistic effects between inorganic clay minerals (e.g., montmorillonite, sepiolite, kaolinite) and bio-based flame retardants (e.g., chitosan-based, lignin-based, phytate-based) have achieved certain progress in the area of polymer flame retardancy. The effects of bio-based flame retardants are exerted through mechanisms such as catalytic char generation and vapour-phase hindrance. However, they have limitations when used alone, including insufficient thermal stability and the need for a high dosage. Inorganic clays form physical barriers through their layered or tubular structures. The high thermal stability of these structures suppresses heat and mass transfer, thereby offsetting the shortcomings of bio-based flame retardants. This synergistic combination greatly improves the flame retardancy of polymer composites, often strengthening their mechanical performance in the process. It therefore offers great potential for the design of multifunctional, eco-friendly flame-retardant polymer composites. Nevertheless, a systematic review of the synergistic mechanisms, fabrication approaches and application progress of different inorganic clay minerals when combined with various bio-based flame retardants is still lacking. Therefore, this article offers a comprehensive review of the current developments of synergistic systems that incorporate various primary clays, such as sepiolite and montmorillonite, with bio-based flame retardants for usage in polymers. Before this, the synergistic flame-retardant mechanism and the key preparation techniques of the composite system were explained in detail. Finally, this article puts forward solutions to the current challenges and sets out prospects for innovation in the designing of flame-retardant materials and the optimisation of processes. The aim is to promote the sustainable growth of efficient, eco-friendly flame-retardant materials.