Preparetion And Performace Evaluation Of Cyclotriphosphazene Containing Unsaturated Bond As An Efficient Flame Retardant For Poly(Ethylene Terephthalate)

With the development of polyester industry, polyethylene terephthalate (PET) has becomethe largest and most widely used production of synthetic materials. However, the limit oxygenindex of PET is low, and the molten drop during burning leads to secondary combustion whicheasy to cause the rapid spread of fire. Therefore, it’s particularly important to develop flameretardant modified PET and improve its flame retardancy. Among various kinds of flameretardants, phosphazenes flame retardant has gradually attracted more attention for its goodthermal stability and flame retardancy. However, as far as we known, the studies on flameretardant performance and flame retardant mechanism of the phosphazenes containing unsaturatedbonds were rarely reported.In this paper, hexakis (4-allylphenoxy) cyclotriphosphazene (PACP) was firstly synthesizedby using hexachlorocyclotriphosphazene as the raw material and characterized by EA, FTIR andNMR. The thermal stability property and thermal cross-linking behavior were investigated byTGA, DSC and RT-FTIR. Then the PET/PACP composites were prepared by melt blendingmethod, and the flame retardant properties and mechanical properties were also studied. It can beconcluded that PACP started crosslinking at about200oC and formed more stable networkpolymer. The PET/PACP composites have excellent self-extinguish property, LOI value was upto33.5%when the content of PACP was only5%(the content of phosphorus was0.33wt.%),UL-94testing was improved to V-0grade from V-2grade, and the tensile strength was only lost20%. Therefore, PET/PACP could establish a good balance between the flame retardantimprovement and the mechanical property loss, and is expected to be applied in the flameretardant field of PET fiber and textile regions.Referring to the structure of PACP, hexakis (4-propagylphenoxy) cyclotriphosphazene (PPT)containing acetylene was also designed, synthesized and characterized. Then the PET/PPTcomposites were prepared by melt blending method. The result showed that PPT could also startcrosslinking at233oC and form network polymer. The PPT has remarkable char-forming propertywith the65wt.%char residue in nitrogen atmosphere. The PET/PPT composites compositesshowed also favorable char-forming performance and the molten drops phenomenon was effectively improved. Unfortunately, the self-extinguish performance of PET/PPT was weak andneed further be improved.