Fire-safe unsaturated polyester resin nanocomposites based on MAX and MXene: a comparative investigation of their properties and mechanism of fire retardancy

Recently, MXene, as a novel graphene-like nanomaterial, has been found to bestow good flame-retardant and smoke-suppression properties to polymers mainly due to the physical barrier effect of its 2D nanosheets. However, a comprehensive investigation of its chemical components as an important factor for these properties has not been conducted to date. To address this issue, herein, MXene (Ti 3 C 2 T x ) and MAX (Ti 3 AlC 2 ) were introduced into unsaturated polyester resin (UPR) at same amounts (2.0 wt%). Their structures are different (multilayer for MXene and bulk for MAX), but the chemical components are similar; therefore, it is important to study the influence of the chemical components of MXene on the fire-safety properties of polymers. In this study, 2 wt% MAX was added to the UPR, and the peak heat release rate (PHRR), the total smoke production (TSP), and carbon monoxide production (COP) of the resulting material were reduced by 11.04%, 19.08%, and 15.79%, respectively; these findings demonstrate the important role of the chemical components of MAX: Ti exerts a catalytic attenuation effect on the UPR nanocomposites during combustion. Moreover, a better fire-safety property of the MXene/UPR nanocomposites (reduction of PHRR by 29.56%, TSP by 25.26%, and COP by 31.58%) than that of the MAX/UPR nanocomposites was achieved, which was due to the physical barrier effect of the MXene nanosheets. This study verifies that in addition to the physical barrier effect, the chemical components play a very important role in the fire safety enhancement of MXene-based nanocomposites. This study perfects the flame-retardant mechanism of MXene for polymer nanocomposites by comparing with MAX, demonstrating the significance of MXene's chemical component during the flame-retardant process, in addition to its physical barrier effect.