A comparative study of POSS as synergists with zinc phosphinates for PET fire retardancy

This paper deals with the fire behaviour of poly (ethylene terephthalate) (PET) filled with Exolit OP950, a zinc phosphinate fire retardant, and three polyhedral oligomeric silsesquioxanes (POSS) having different chemical structures. Regardless of the POSS type, intumescence occurs during combustion, but the insulation properties of the chars produced are different. Best reductions on total heat evolved (THE) and on cumulative CO2 with no increase in CO emissions are observed when dodecaphenyl POSS is used. This may be related to its thermal degradation pathway, releasing via this process volatile organic species contributing on intumescence and producing an effective protective layer having a foliated structure.