| Polyester (PET) fibers, because of their outstanding characteristics of high strength, resistance to shrinkage and stretch, good dyeability, and chemical resistance, are used extensively in clothes, carpets and furnishings. However polyester fibers belong to melting flammable fibers. Flame-retarded treatment of PET fibers has become to a research tendency of great concern in reducing the dangers of PET fibers involving fire incidents. This research deals with the preparation of flame-retarded PET resins and fibers by using new types of flame-retardant additives: brominated phosphate compound (FR-A), brominated aromatic polymer (FR-B) and polybenzphosphonate(FR-C) by means of melt extrusion, and than flame-retarded PET fibers were made by adding high flame retradant contents master batch in pure PET chips.The effects of flame-retardants on combustion, thermal degradation, crystallization and rheological propertives of PET have been investigated using L0I tester, CONE Calorimeter, Thermogravimetric Analysis, Differential Scanning Calorimetry and Instron 3211 capillary rheometer separately. Some conclusions can be drawn as follows:The limited oxygen index (LOI) of flame retarded PET which contain three kinds of flame retradants obviously higher (all above 27) than the untreated sample. FR-A has made the greatest increase in LOI of flame-retarded samples comparing with the pure PET. All combustion parameters (such as THE, EHC, RHR) of flame-retarded samples measured from CONE calorimeter were strongly depressed after adding flame-retardants. FR-A has been proved very effective. Next is FR-C and then is FR-B. The SEA parameter increases by adding flame-retardants indicating that more smoke has produced due to the presence of FR. Smoke Ratios grow when adding FR-A and FR-B, but decrease when adding FR-C.The intrinsic viscosities and the average degrees of polymerization of flame retarded PET are lower than the untreated sample and reduce the values with the increase of FR contents. But because there are not a significant changing in intrinsic viscosities in general, the values basically between 0.58~0.64, the requirements of processing and spinning can be met. The intrinsic viscosities of flame-retarded samples that contain FR-C have the lowest decrease. Borminated phosphate FR has obviously accelerated the degradation rate of PET and this also has been proved by the degradation kinetics analysis. This kind of accelerate degradation phenomenonreduce when using FR-B and FR-C instead. The degradation was found to be a complex process of at least three overlapping stages for which kinetic calues can be calculated. The results indicate that FR-A has reduced the activation energies and has obviously accelerated the degradation rate of PET.The products of pyrolysis of untreated and flame retarded PET have been studied using gas chromatography/mass spectrometry technique combining with CONE data. A mechanism of two-phase pyrolysis for PET degradation is first timely proposed. The first step in the degradation is most probably the classical ester scission reaction to give a carboxylic acid and olefinic end groups. Further ester scission on the adjacent ester groups of carboxylic acid and olefinic molecular chains can then lead to the formation of lower weight pyrolytic products, such as: CH2=CHOCOPhCOOCH=CH2, CH2=CHOCOPhCOOH and HOOCPhCOOH, and they can pyrolyze continually to produce substrate pyrolytic compounds, such as: HOOCPhCOCH3, PhCOO, PhH, PhCOCH3 and CO, CO2 . At the same time, a corsslinking cyclization reaction occurred of the formation of the gas products during the degradation of PET. This step ultimatly produce a kind of cycloolefin structure. FR-B involved only gas-phase mechanism, while FR-A and FR-C involved both gas-phase and solid-phase mechanism.Tg,Tgc,Tm,Tmc of flame retarded samples have been reduced by the presence of flame-retardants. They also make the crystallization of PET easier during low temperature range, but more difficult among high temperature range. FR-B has the smallest infl...
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