A review of over 120 science publications summarises current research into PIN flame retardant solutions for thermoplastics. It is noted that PIN FR solutions can avoid the problems of toxic and corrosive gases and black smoke generated by halogenated FRs. Developments in main PIN FR technologies are discussed, including for inorganic FRs (ATH, MDH), e.g. inorganic coating carbon microspheres, zirconium phosphate (ZrP) and organo-modified ZrP, aluminium hypophosphite, aluminium diethylphosphinates, ammonium polyphosphate (APP), e.g. hydroxyl functionalised or microencapsulated, melamine and derivatives (MCA) such as melamine polyphosphate, DOPO and derivatives, other phosphorus derivatives, bio-derived PIN FRs and synergistic combinations of different PIN FRs, e.g. with silicates and clays. The review shows the high level of current research into PIN FR solutions and the potential for innovation, particularly in developing solutions with lower FR loadings to minimise impact on polymer performance and to reduce costs, and the importance of improving the flame retardant – polymer interface.
“Review Paper. Halogen‑free flame retardants for application in thermoplastics based on condensation polymers”, N. Levinṭa et al., Springer Nature Applied Sciences, 2019, 1:422 https://doi.org/10.1007/s42452-019-0431-6