A detailed (32 page) review of chemical synthesis of organophosphorus PIN flame retardants outlines different types of chemical structure developed, different chemical reaction pathways for synthesis and their likely industrial / economic feasibility and available information on the fire performance and material characteristics of different molecules generated. The review highlights recently developed aromatic DOPO-based phosphinate compounds which offer thermal stability >250°C and so potential applications in polymers such as polyesters and polyamides. The authors note the need to consider both complexity of synthesis (economic feasibility), durability and toxicity/environmental impact in research into new molecules.
“Recent Developments in Organophosphorus Flame Retardants Containing P-C Bond and Their Applications”, S. Wendels et al., MDPI Materials 2017, 10, 784; https://doi.org/10.3390/ma10070784