| Some analytical technologies and methods were used to study the flame-retardant action modes of three kinds of phosphorus-containing flame retardants for PET, especially the effects of flame retardants on the pyrolysis of PET and the corresponding flame-retardant mechanisms. The flame retardants used here were a kind of thermotropic liquid crystal copolyesters (TLCP) containing phosphorus derived from 2-(6-oxide-6H-dibenz〈c, e〉〈1, 2〉oxa phosphorin-6-yl)-1,4 -dihydroxyphenylene, 4-hydroxybenzoic acid, terephthalic acid and isophthalic acid, 9,10- dihydro-9-oxa-10-(2,5-dihyroxyphenyl) phosphaphenanthrene-10-oxide) thiophenylphosphonate (PDPTP) and 9,10-dihydro-10[2,3-di(hydroxycarbonyl)propyl]10-phosphaphenanthrene-10-oxide (DDP). TLCP and PDPTP were used as additive flame retardants, and DDP as a reactive flame retardant which was reacted into the macromolecules of PET in the existence of organomontmorillonite (O-MMT).Analysis of PY-GC-MS indicated that there were little influences of these flame retardants on the compositions of pyrolysis of PET, but the concentrations of some compounds were greatly changed. That means the existence of flame retardants did not alter the mechanism of pyrolysis of PET, but strongly retarded some pyrolysis reactions, especially extending pysolysis reactions. Moreover, they also have drastic effects on the balance of some competitive reactions.TG analysis indicated that the phosphorus containing flame retardants were able to decrease Ti , Tmax and mass loss in the first stage of thermal decomposition of PET. However, the mass loss in the second stage of FR polyesters is higher than that of PET.TG-FTIR analysis indicated that the phosphorus in TLCP and PDPTP mainly existed in the condensed phase in the initial stage of thermal decomposition of polymers, and it would react with oxygen in the air or in polymers to produce phosphorus acid and metaphosphoric acid,...
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