Bio-sourced phosphorus FR for epoxy resins
Isosorbide can be readily produced from starch, which is widely available from plants such as wheat seeds or potatoes. It is a dihydroxyl ether (diether diol) which can be converted to isosorbide bis- phosphorus ethers (phosphates, phosphinates or phosphonates).
This is achieved by using phosphoryl chloride or phosphite and a chlorinated solvent (the chlorine is a carrier and is not transferred into the isosorbide bis- phosphorus esthers).The isosorbide bis-phosphorus esters were tested as PIN flame retardants for DGEBA epoxy resin. A 1% phosphorus loading (c. 12% FR) was sufficient to reduce peak heat release rate PHRR by 40-50%, improve Limiting Oxygen Index (LOI) by 25-50% (to LOI > 25) and achieve UL94-V1 at 3.2 mm thickness.
“Flame retardant properties of isosorbide bis-phosphorus esters”, Y. Daniel & B. Howell, Polymer Degradation and Stability 2017 http://dx.doi.org/10.1016/j.polymdegradstab.2017.04.005