Semiamorphous Fe-BDC: The missing link between the highly-demanded iron carboxylate MOF catalysts

An eco-friendly flame retardant from chitosan, phytic acid, Fe-MOF endows thermoplastic polyurethane with enhanced fire safety and mechanical property based on hydrogen bond and π-π stacking

Currently, achieving a satisfactory balance between flame retardancy and mechanical properties of thermoplastic polyurethane (TPU) composites faces significant challenges. To address these challenges, in this paper, an eco-friendly flame retardant from chitosan (CS), phytic acid (PA), and Fe-MOF (CS@PA@Fe-MOF) was synthesized and then introduced to TPU matrix. The non-covalent interaction including π-π stacking and hydrogen bonding that exist between the CS@PA@Fe-MOF units and TPU molecular chain can improve the interfacial compatibility of TPU composites, and contribute to imparting exceptional fire safety and superior mechanical performance to TPU composites. It has been found that the peak heat release rate (pHRR) and total heat release (THR) of TPU/1%CS@PA@Fe-MOF composites were decreased by 54.9 % and 38.8 % compared with those of pure TPU, respectively. The improvement of fire safety is attributed to the multiple synergistic effects, including the formation of an intumescent char-barrier, catalytic carbonization, and radicals trapping during the combustion process of TPU/CS@PA@Fe-MOF composite. Importantly, the mechanical properties of TPU/CS@PA@Fe-MOF composite have been significantly improved. The tensile strength and elongation at break of TPU/1%CS@PA@Fe-MOF increased by 15.2 % and 7.1 % compared with those of pure TPU, respectively. This work provides an eco-friendly and efficient strategy for the design of TPU composites with both superior flame-retardant and mechanical properties.