The preparation of starch derivatives reacted with urea-phosphoric acid and effects on fire performance of expandable polystyrene foams.

A novel bio-based flame retardant, ammonium phosphate starch carbamates (APSC) was synthesized from starch, phosphoric acid and urea to achieve better thermal stability and char formation. Flame retardant expandable polystyrene foams (EPS) were prepared by coating method with APSC. The fire resistance evaluation of EPS composites by limiting oxygen index (LOI), vertical burning (UL-94) and cone calorimeter tests indicated that the addition of 47 wt.% of APSC enhanced the LOI from 17.6%-35.2%, with V-0 rating in UL-94, and decreased the peak heat release rate from 666 kW/m2 to 316 kW/m2. Moreover, the total smoke production was also sharply decreased from 70 m2 of pure EPS to 17 m2. By the presence of APSC, the substantial char formation prevented the heat and oxygen transfer, and interrupted the releasing of flammable products, thus protecting the EPS foam from burning.