Alkyl sulfone bridged phosphorus flame-retardants for polypropylene

Three novel alkyl sulfone bridged phosphorus (P) compounds namely 6,6′-(sulfonylbis(ethane-2,1-diyl))bis(dibenzo[c,e][1,2]oxaphosphinine 6-oxide) (SEDOPO), sulfonylbis(ethane-2,1-diyl))bis(diphenylphosphine oxide) (SEDPPO), and tetraphenyl (sulfonyl bis(ethane-2,1-diyl)) bis(phosphonate) (SEDPP) (i.e. phosphine oxide, phosphinate phosphonate, respectively) were synthesized via a Michael addition reaction with good yields (≥ 85%) at 200-g scale. They exhibited thermal stability above 250 °C, which allowed them to be melt-processed polypropylene (PP) formed into thin films (~ 0.6 mm). Rheological measurements of the PP blends typical shear thinning behavior provided evidence for compound's thermo-oxidative stabilizing effect. This was also confirmed by analysis showing that PP-SEDOPO PP-SEDPPO higher (~25 °C) than blank PP; however, PP-SEDPP had smaller impact. Small scale fire tests PP-FR flame retardant efficacy new P-compounds. Cone calorimetry on showed reduction in heat release rate (HRR) (~48%) compared PP. Further evolved gas P-compounds are primarily active gas-phase.