Novel Cyclotriphosphazene Derivatives-silicon Systems And Study On Flame Retardancy And Mechanism For Poly (Ethylene Terephthalate)

Poly(ethylene terephthalate)(PET) is a semi-crystalline thermoplastic polyester, which is largely used for clothing industry, decorative fabrics and packaging materials to meet multifarious requirement in daily life due to its low cost and excellent mechanical as well as dimensional stability. However, the high flammability and serious dripping during burning of the polymer limits its use when the requirement of fire safety was considered. Many studies on improving the fire resistance of PET have been reported, such as copolymerizing flame-retardants into the molecular chains, incorporating flame-retardants into the resin and laying over a functional coating by textile finishing. In the past few decades, the flame retardancy and anti-dripping of PET in fire have faced a big challenge, because some flame-retardant mechanisms depend solely on the activity in gasous phase, which aggravated the melt-dripping and availed PET self-extinguishing. It is well known that serious melt-dripping during the fire might lead to secondary damage, such as spread of the fire and immediate empyrosis. Therefore, it is important to develop char formation、anti-dripping and flame retardancy of PET to more extensive application. In this paper, the flame retardant effect and mechainsm of PET composites were carried out by incoportered into phosphour nitriles derivatives or their combiend with silcon compounds, which was systhesised by the precursor(hexachlorocyclotriphosphazene). Finally, based on the actual application, the mechaincal properties and flame retardant of PET nanocomposoties was investigated in order to recovering the lose strength of PET martix during melting blend with phosphour nitriles derivatives.The main research work is as follows:(1) Two kinds of cyclotriphosphazene derivatives(ortho-allyl phenol derivative of cyclophosphazene(OACP) and para-allyl ether phenol derivative of cyclophosphazene(PACP)) were prepared based on hexachlorocyclotriphpsphazene, respectively. They, together with commercial flame retardants(phenol derivative of cyclotriphosphazene(PNCP)), were respectively used as filler to modify the flame retardant properties of poly(ethylene terephthalate)(PET) by melting-blending. The results showed that cyclophosphazene(CP) bearing para-allyl phenol groups was far more effective than CP with phenol groups or ortho-allyl phenol groups, only little PACP(0.37 wt% phosphorus) was enough to increase the limiting oxygen index value with 33.5 vol.%, UL 94 V-0 rating. From the mechanism analysis, during the process of melting blend, the ecithermic Claisen rearrangement products of the para-allyl ehters in PACP played a key role in the balance of the flame-retardant and mechanical properties of PET composite.(2) A novel phenylethynyl terminated cyclotriphosphazene oligoimides(hexakis(4-phenyl acetylene imide phenoxy) cyclotriphosphazene, HPAIPC) was synthesized to solve the conflict between the flame retardance and anti-dripping of PET. The flame-retardancy and anti-dripping properties of the PET/HPAIPC composites were investigated. The results revealed that thermal stability, self-extinguish and inhibition of melt-dripping properties of PET/HPAIPC composites were obviously enhanced by the introduction of high-temperature auto-crosslinking cyclotriphosphazene oligomides into polyester. All results of rheological analyses, pyrolysis products and the morphology of the char demonstrated that the HPAIPC could exhibit a greater complex viscosity, enhance the physical barrier effect to retard the flammable gases, heat flux and flame.(3) Hexakis [p-(hydroxymethyl)phenoxy] cyclotriphosphazene(PN6) was prepared by two-step reaction, and then, PET/PN6/poly(2-phenylpropyl) methylsiloxane(PPPMS) composites were prepared, the flame-retardancy and anti-dripping properties were also investigated. The results indicated that the contents of PN6 and PPPMS had great effect on the melt behavior, crystallization and thermal properties of PET composite. The introducing of PN6 and PPPMS into PET would accelerate the char formation and anti-dripping during the flame-retardant PET combustion process. The analysis of morphology and chemical components of the charred residue displayed a synergistic effect of the PET/ PN6/ PPPMS system by providing a compact and intact barrier and promoting the accumulation of silicon elements in the outer surface of char residues.(4) A novel silicone-containing triazine oligoimides charring agent(STCA) was synthesized via polycondensation, which was combined with commercialized PNCP to flame retardant poly(ethylene terephthalate)(PET). The PET/PNCP/STCA composites were prepared by direct melt compounding and the flame-retardancy properties and thermal degradation behaviors of which were investigated. The results revealed that, as the intumescent flame retardant(IFR) contained mass ration of PNCP and STCA was 3:1, STCA exhibited a best synergistic effect with PNCP in flame retardant PET, and excellent thermal stability. This effect synergistic effect was attributed to the acid buffer action enhanced the acid catalytic charring to higher temperature range, as well as the surface compact and bumping charred barrier containing phosphorus and silicon elements protected PET composites during combustion.(5) Aiming to overcome the nagative effect of the PET/PACP mechanical performance, the effect of trissilanolphenylpolhedral oligomeric silsesquioxane(T-POSS) on the mechanical and flame retardant performace was inverstaged. T-POSS and PACP with differert proportion was pre-dispersed in acetone solution, and the flame retardant hybrids was further prepared by melt blending method at low loading. Morphological analysis(TEM) revealed that the T-POSS was dispersed well in the PET matrix. It was found that the T-POSS and PACP in the appropriate ratio was favorable for improving the mechanical and flame retardance of the hybrid composites by microscale combustion calorimeter(MCC), dynamic mechanical analyzer(DMA) and so on.