Synergistic flame retardancy of bis(1‐methoxy‐2,2,6,6‐tetramethylpiperidin‐4‐yl)sebacate and aluminium hypophosphite/melamine hydrobromide in PP

Abstract

SummarySynergistic flame retardancy of bis(1‐methoxy‐2,2,6,6‐tetramethylpiperidin‐4‐yl)sebacate (NORSM) and aluminium hypophosphite (ALHP)/melamine hydrobromide (MHB) in polypropylene (PP) was studied by limiting oxygen index (LOI) determination, UL‐94 test and cone calorimetry test. The results reveal that NORSM, together with ALHP/MHB, has an exceptional synergistic flame retardant effect in PP. For the FR‐PP containing 1.0 wt% of ALHP and 1.5 wt% of MHB, combining NORSM in 0.30 wt% concentration can make its LOI increases from 19.0% to 26.3%, the flame retardant effectivity increases from 0.48 to 3.04, the synergistic effectivity is as high as 2.03, the UL‐94 rating is improved from none to V‐2, the fire performance index increases from 58.7 to 91.3, various heat release parameter values are reduced obviously. It is confirmed that NORSM plays the role of synergism with ALHP/MHB mainly through the following mechanisms: the active radicals such as methyl radicals, methoxy radicals, nitro radicals, and aminyl radicals produced by the pyrolysis of NORSM, together with PH3 and HBr, quench active free radical such as ·OH, so the chain reaction of combustion is interrupted and results in a more efficient flame retardant effect in gaseous phase.