Effect of phosphorus flame retardants on the flammability of sugar-based bioepoxy resin.

The flame retardancy of sorbitol-based epoxy resin is targeted. From the bioepoxy 3% phosphorus-containing matrix samples were prepared. Surprisingly, only HB classification of UL-94 test was reached with the application of ammonium polyphosphate (APP) and resorcinol bis(diphenylphosphate) (RDP). V-0 was reached in the case of red phosphorus (RP) and ammonium salt of DOPO (DXA), while the melamine salt resulted in HB rating, due to the lower P-content of the sample. In the meantime, the highest LOI value was reached in the case of APP. The V-0 red phosphorus composition, however, has an LOI of as low as 25 V/V%. In the case of the thermogravimetric analysis, the application of red phosphorus resulted in significantly increased thermal stability, but faster degradation than in the case of the reference. The RDP showed somewhat decreased stability, due to the less stable phosphorus ester bonds. The amount of the charred residues is increasing with the flame retardant content, but to different extents depending on the type of flame retardant. The highest values were reached with APP. Regarding the cone calorimeter results; the lowest heat release rate belongs to the APP-containing sample, while the V-0 compositions (RP and DXA) show poorer performance in this respect. [ABSTRACT FROM AUTHOR]