Phosphorus‐Based Flame Retardants

Because phosphorus chemistry is very diverse there are many classes of phosphorus- based flame retardants with specific applications. Red phosphorus is a unique flame retardant which is used in its elemental form. Despite being very flammable in air, red phosphorus is a very efficient flame retardant mostly for thermoplastic polyesters and polyamides. Most inorganic phosphates are water soluble and because of this they are used as non-durable treatment for textiles and wood. Water insoluble ammonium polyphosphate, piperazine polyphosphate and melamine phosphates are very efficient flame retardants especially for polyolefins. Aluminum and calcium hypophosphites and aluminum diethyl phosphinate were introduced to the market about two decades ago but are still actively researched for new applications by industrial labs and for mechanisms of action by academic institutions. Aliphatic phosphates and phosphonates and aromatic phosphates are the oldest classes of organophosphorus flame retardants and plasticizers with well-established applications. Aromatic bisphosphates are broadly used in polycarbonate- based and polyphenylene ether-based blends but their market share grows mostly because these types of thermoplastics grow fast. Fueled by a fast growing sector of high speed and high frequency printed wiring boards, aromatic phosphinates, phosphine oxides and phosphazenes are the most active areas of research both in industry and in academia.