Recycling of flame-retardant polymeric materials: State of the art and future perspectives

Polymeric materials have been widely used for several applications, due to their good overall performances. This extensive use leads to a huge amount of polymeric waste. Like virgin thermoplastics, the flame retardant (FR) versions are the major contributions to flame retardant polymeric wastes. Most of plastics can be easily reprocessed by extrusion, however, the presence of halogenated compounds creates hurdles in their recycling, as some of these halogenated flame retardants are regulated. The management of plastic wastes containing non-halogenated FRs is also challenging, as it strongly depends on the water content and chemical composition of the plastic waste stream. Besides, the presence of a permanent cross-linked network in the polymer matrix of end-of-life FR thermosetting products makes their recycling challenging. Unfortunately, current recycling methods do not involve the recovery of the thermoplastic/thermoset matrix and do not take into account the presence of toxic FRs in the polymer network. The scientific community is developing lower-energy and sustainable strategies, which include the synthesis of recyclable inherently FR thermosets composed of covalent adaptable networks (CANs). This chapter aims to provide a detailed overview of the currently applied methodologies for the recycling of FR thermoplastics, conventional FR thermosets, and inherently FR thermosets based on CANs.