Study On Synthesis Of Polyaminocyclotriphosphazene And Its Flame Retardance In Polyolefin

Phosphazene as the flame retardants has some merits such as non-halogen, less smoke, high flame retardant efficiency, non-toxicity and non-corrosive gas formed when burning. So it has become the direction of the development of flame retardants. Hexaamidocyclotriphosphazene is one of a few commercialized phosphazene flame retardants. However, its practical application has been strictly limited due to its high water solubility and only for the textile fibers, so how to reduce its water solubility becomes the key to expanding the application scope.In this paper, polyaminocyclophosphazene (PHACTPA) was synthesized by polycondensing hexaamidocyclotriphosphazene. The results indicated that the substitution degree of aminocyclotriphosphazene had significant impact on its polycondensation. With the increasing of substitution degree, the polymerization yield increased first and then decreased, the content of free chlorine and combined chlorine decreased gradually, contrary to the solubility and hygroscopicity. The optimum polycondensation conditions were as follows:the substitution degree being92.6%, the reaction temperature being178～182℃,polymerization time being0.5h. Under the above conditions, the yield of PHACTPA was94.32%, and the content of chlorine, nitrogen, phosphorous and hydrogen in the product were respectively2.05%,50.89%,43.38%and3.68%as well as the solubility of the product was1.05g/100mL and the hygroscopicity was5.9%under relative humidity of50%～60%. The PHACTPA obtained was mainly composed of dimer, trimer, tetramer and pentamer of aminocyclotriphosphazene, especially the trimer. Due to the high content of phosphorous and nitrogen, better thermal stability and nearly neutral, PHACTPA was perfectly used as an additive flame retardant. The flame retardancy of PHACTPA in polyolefin was studied. The experimentshowed the flame retardancy of PHACTPA on polyethylene (PE) and polypropylene(PP) was not very ideal, but there was an excellent synergistic flame retardantcy ofPHACTPA and THEIC in PE and PP. With20wt.%dosage, the LOI of FR-PE andFR-PP with PHACTPA was24.4％and25.2％respectively, the vertical burning ratingwas failed and V-1respectively，and the LOI of FR-PE and FR-PP with THEIC was17.4％and18.7％respectively, all vertical burning rating failed. However, FR-PE andFR-PP with the combination of PHACTPA and THEIC had the25.4%and27.4%ofLOI, and passed the V-0classification.The analysis of cone calorimeter indicated thattotal heat release(THR), peak heat release rate (PHRR), average heat release rate(MHRR), ignition time (TTI) of PHACTPA/THEIC/PE were lower thanPHACTPA/PE, but contrary for PP. TGA results indicated PHACTPA orPHACTPA/THEIC has the little effect on the thermal stability of the materials.Residues analysis revealed PHACTPA and PHACTPA/THEIC played a flameretardancy mainly by condensed phase mechanism, where PHACTPA was decomposedinto non-volatile phosphoric acid compounds and promoted charing of PE or PP, andCO2, NH3and N2released from the decomposition of PHACTPA and THEIC foamedthe residues, the formed intumescent layer resulted in the barrier effect on heat, air anddecomposition products. THEIC promoted the decomposition PHACTPA tophosphoric acid compounds, so improved PE and PP charring, which resulted in anexcellent synergistic flame retardantcy.