MXene based core-shell flame retardant towards reducing fire hazards of thermoplastic polyurethane

Abstract Amounts of heat and toxic fumes are released during the combustion of polymeric materials, which severely threats to the human health and causes the environmental pollution. Therefore, it is vital to find an effective way to address these problems. Herein, titanium carbide (Ti3C2Tx) and chitosan (CS) were firstly adopted to functionalize ammonium polyphosphate (APP) via the microencapsulation and layer-by-layer assembly. Afterwards, the as-synthesized core-shell-structured hybrid (APP@CS@Ti3C2Tx) was used to enhance the interface compatibility, thermal stability and fire safety of thermoplastic polyurethane (TPU) composites. The results demonstrated that the APP@CS@Ti3C2Tx hybrid presented a strong interface interaction with the TPU matrix. Besides, TPU/APP@CS@Ti3C2Tx composites exhibited the improved thermal stability. The TPU composite containing 9.5APP@CS@0.5Ti 3C2Tx achieved V-0 rating in the UL-94 testing. The cone calorimetry results illustrated that introduction of 9.5APP@CS@0.5Ti 3C2Tx into TPU caused remarkable reduction in the total heat release (73.0%) and total smoke release (77.3%). Furthermore, the total carbon monoxide yield and total carbon dioxide yield of TPU/9.5APP@CS@0.5Ti3C2Tx were significantly decreased by 75.3% and 75.4%, respectively, compared to those of pure TPU. The synergistic charring effect between APP@CS and Ti3C2Tx, the thermal oxidization action and “tortuous path” effect of Ti3C2Tx nanosheets combined with the trapping effect of APP@CS resulted in the dramatically improved fire resistance of the polymeric material. This work offers an innovative strategy to fabricate the high-performance polymer composites with superior fire safety.