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In this work, para‐aramid fibers were dispersed into para‐aramid nanofibers (ANF) by deprotonation process, and then modified by 3‐chloropropyne (PC) via covalent bonding interaction. The resultant nanofiber (ANF‐PC) as a flame retardant was blended with thermoplastic polyurethane (TPU) to obtain fire‐retardant TPU nanocomposites. The addition of 0.250 wt% ANF‐PC reduced the peak heat release rate, total heat release, total smoke release, and peak CO release rate of TPU by 47.7%, 31.5%, 16.4%, and 45.1%, respectively. The char yield of TPU/ANF‐PC0.250 was increased from 7.7% (TPU/ANF0.250) to 13.7%. The flame‐retardant effect of ANF‐PC in TPU composites can be attributed to its carbonization effect in the condensed phase, which increased the char yields and graphitization degree of char residue. In addition, the presence of ANF‐PC increased the tensile strength and breaking strain of TPU by 645% and 578% compared to untreated ANF, due to the improved dispersion state of ANF‐PC.

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A novel hydrophobic rare earth‐based aluminum hypophosphite (AHP) was prepared using rare earth aluminate coupling agent (REA) in a ball mill with a one‐step mechanochemistry method, and used as flame retardant for epoxy resin. It has been found that RaAHP‐4 (AHP was modified by 4 wt% REA) exhibited excellent hydrophobic properties with the water contact angle of 94.58°. The effect of RaAHP‐2 (AHP was modified by 2 wt% REA) and RaAHP‐4 on the flame retardancy, thermal stability, and hydrophobic properties of EP/6RaAHP‐2 and EP/6RaAHP‐4 composites were investigated. It has been found RaAHP‐2 and RaAHP‐4 can significantly improve the flame retardant performance of EP/6RaAHP‐2 and EP/6RaAHP‐4 composites. And the peak heat release rate (PHRR) and total heat release (THR) values of EP/6RaAHP‐4 were reduced by 50.44% and 35.59% compared with pure EP, respectively. Moreover, the maximum peak value of CO production rate from EP/6RaAHP‐4 decreased by 62.64% compared with that from EP/6AHP. The excellent flame retardant effect of EP/6RaAHP‐4 composites was obtained because RaAHP‐4 changed the formation of the char residue layer during the combustion process. In comparison, the compactness, expansion degree, and carbonization quality of the char residue layer from the samples with RaAHP‐2 or RaAHP‐4 have been significantly improved, which acted as a valuable barrier for heat and mass transfer. The above results showed that the one‐step synthesis method had high potential application in the large‐scale production of hydrophobic AHP.