Phosphoric acid
Phosphoric acid derivatives of isosorbide are explored as an environmentally friendly alternative to halogen-containing flame retardants. So far, 1,2,5,6,9,10-hexabromocyclododecane (HBCD) has been widely used as a flame retardant in extruded polystyrene foam (XPS) in the construction and insulation sector, but it was as SVHC (substance of very high concern) banned from manufacturing and application in May 2013. Phosphorus-based isosorbide compounds, such as isosorbide bis (diphenyl phosphate) [ISTP] are considered as a replacement.