Preparation of soybean root-like CNTs/bimetallic oxides hybrid to enhance fire safety and mechanical performance of thermoplastic polyurethane

Abstract

The three main fatal factors considered when Thermoplastic polyurethane (TPU) products catch fire are massive heat radiation, suffocation by smoke inhalation, and poisoning by toxic gases (CO and HCN). In this study, to weaken these adverse impacts, soybean root-like zeolitic imidazolate frameworks (ZIFs)-derived carbon nanotubes/bimetallic oxides (CNTs/BMO) hybrids are designed and prepared. In addition, we studied its performance in improving the fire safety of TPU. The in-situ growth of ZIFs on the surface can suppress the entanglement of CNTs (main roots), enhancing a uniform dispersion in the hybrid. Porous BMO and ultrathin N-doped CNTs (N-CNTs) functioned as conversion stations for organic and inorganic, similar to the root nodules and root hairs, respectively, resulting in the increased generation of char residues and suppressed emissions of smoke and toxic gases. Compared with neat TPU, there are 32.11%, 27.91%, and 41.91% reductions in peak heat-release rate, total smoke production, and total CO production, respectively, with 1 wt% of well-dispersed CNTs/BMO hybrids. In addition, the soybean root-like hybrids also have enhanced the mechanical performance of composites. On the basis of the satisfactory mechanical strength of neat TPU, the tensile strength and elongation (at break) of the soybean root-like hybrids are further increased by 70.61% and 16.49%, respectively. This work provides a feasible method to construct a well-dispersed inorganic hybrid with complex structure and excellent performance, which will deliver a new perspective for the development of multifunctional polymer composites.