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

Abstract

Summary Synergistic 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.

Fire‐retardant synergy of bis(1‐methoxy‐2,2,6,6‐tetramethyl‐4‐piperidinyl)sebacate and melamine hydrobromide/aluminum diethylphosphinate in polypropylene

“…These results indicate that NORSM is first cracked into methoxy and aminyl radicals (Scheme 1), which are then rapidly transformed into stable products because they are very active. Therefore, they were not detected by MS, which is consistent with the analysis results of Py‐GC/MS 21,23 …”

“…Finally, the plates were cut into standard sizes for fire‐retardant property tests. The formulations of the PP composites were designed in accordance with the literature, 23 and they are summarized in Table 1.…”

“…The fire retardation effectivity (EFF) and synergistic effectivity (SE) were calculated according to the formula reported in the literature 23 …”

“… 19 Bis(1‐octyloxy‐2,2,6,6‐tetramethyl‐4‐piperidinyl)sebacate exhibits good light stabilization and good fireproofing synergy with brominated phosphate in PP fiber, which could pass the FMVSS 302 test when the loading of the brominated phosphate and Tinuvin NOR123 was 2 wt% and 1 wt%, respectively 20 . Wu et al established that bis(1‐methoxy‐2,2,6,6‐tetramethyl‐4‐piperidinyl)sebacate (NORSM) and tris(1‐methoxy‐2,2,6,6‐tetramethyl‐4‐piperidinyl)phosphite (NORPM) exhibited a good fireproofing synergy with tri(tribromophenyl) cyanurate/Sb 2 O 3 in high‐impact polystyrene 21,22 and MHB/ALHP in PP 23,24 …”

“…20 exhibited a good fireproofing synergy with tri(tribromophenyl) cyanurate/ Sb 2 O 3 in high-impact polystyrene 21,22 and MHB/ALHP in PP. 23,24 Although ALHP/MHB/NORSM and ALHP/MHB/NORPM exhibit good fire retardation in PP, they have significant environmental and safety problems because of released hypertoxic PH 3 when ALHP is heated. 5 Aluminum diethylphosphinate (ADEP) exhibits exceptional thermal stability and fire retardation, and no PH 3 is produced during its thermal decomposition; thus, it is safe.…”