The influence of synergistic effects of hexakis (4-nitrophenoxy) cyclotriphosphazene and POE-g-MA on anti-dripping and flame retardancy of PET

In this report, hexakis (4-nitrophenoxy) cyclotriphosphazene (HNCP) and ethylene–octene copolymer grafted-maleic anhydride (POE-g-MA) were blended with pure PET together. The fire retardant ability and thermal stability of PET/HNCP/POE-g-MA were investigated respectively. The results indicated that HNCP and POE-g-MA had a synergic effect on the dripping resistance of PET besides the enhancement in flame retardancy to a certain degree. LOI values of the polymers with both POE-g-MA and 10 wt%HNCP were higher than that of pure PET and no drips just containing 1 wt%POE-g-MA. The reason was that HNCP could be well dispersed in PET when POE-g-MA was added, forming a more effective char layer and preventing dripping of polymers. Indeed, the morphology of charred residue of PET/HNCP/POE-g-MA showed that a porous protective layer with a dense surface was formed. The thermogravimetric analysis revealed that addition of HNCP improved the thermal stability and the yield of char residue of the PET/POE-g-MA systems. Based on a series of experiment results, the synergistic effect of HNCP and POE-g-MA on the anti-dripping of PET was also discussed. In the PET/HNCP/POE-g-MA system, POE-g-MA played a role of compatibilizer. The improved compatibility and dispersion provided the composite with the ideal flame retardancy, thermal stability and anti-dripping property.