Recent developments in the fire retardancy of polymeric materials

The widespread applications of polymeric materials require the use of conventional flame retardants based on halogen and phosphorous compounds to satisfy fire safety regulatory standards. However, these compounds, particularly halogen-based examples, are persistent organic pollutants of global concern and generate corrosive/toxic combustion products. To account for eco-friendliness, ultimate mechanical/physical properties and processing difficulties, the window of options has become too narrow. Although the incorporation of non-toxic nanofillers in polymers shows positive potential towards flame retardancy, many obstacles remain. Moreover, most of the literature on these materials is qualitative, and often points to conflicting/misleading suggestions from the perspectives of short-term and long-term fire exposure tests. Hence, there is a renewed need to fundamentally understand the fire response of such materials, and complement experimental results with theoretical modelling and/or numerical simulation. A part of this review will highlight the ecological impacts of using conventional flame retardants, thereby signifying the necessity to use eco-friendly agents. In other sections, we explore the use of various nanofillers for this purpose, compare their performance with traditional systems, provide insights into different testing standards and combustion mechanisms, modelling aspects of the combustion behavior, and identify novel approaches that could be considered for meeting the fire safety standards with eco-friendly materials.