Effects Of Coal And Fluoropolymers On The Structure And Properties Of Polyester

The purpose of this thesis is to investigate the effects of coal, ammonium polyphosphate (APP) and their combination system, fluoropolymers on the structure and properties of poly(ethylene terephthalate) (PET) and phosphorus-containning copolyester (fPET). The flame-retardant properties of the modified PET and fPET were studied with limited oxygen index method, horizontal and vertical burning methods as well as charring experiments. Thermal behavior, thermal degradation characteristics and flame retardant mechanism of the two polyesters were studied with the cone calorimetry and thermogravimetry. Differential scanning calorimetry (DSC) was used to analyse crystallization of the polyesters. In addition, the mechanical properties of the modified PET and fPET were tested with multipurpose test machine. The rheological properties of the modified polyesters were evaluated with the parallel plate rheometer. Finally, the bench scale spinning experiments including spinning and drawing and texturing were carried out for the copolyester in the presence of additives. The mechanical properties, flame-retardancy and dyeing of the copolyester fibers were assessed.Effects of coal and fluoropolymers on the structure and properties of polyester The main important findings are as follows:(1) APP accelerated thermal degradation of PET and of fPET. Coal/APP flame retardant system has synergistically improved the charring and flame retardant properties of PET and fPET. The results from Cone calorimetry showed that, the Coal/APP flame retardant system significantly reduced the heat release rate (HRR) and the peak heat release rate (pk-HRR) of PET, and the flame retardation of the Coal/APP system was evidenced in the condensed phase. Unfortunately, the mechanical properties of the PETs were deteriorated in the presence of the Coal/APP system.(2) Fluoropolymer PA5935 accelerated thermal degradation and reduced oxygen index of the two polyesters, although it multiplied the char production at high temperatures. PA5935 decreased the degree of crystallization and thus mechanical properties of PET. PA5935 promoted the cold crystallization and increased the degree of crystallization and thus mechanical properties of fPET. The irregular changes of oxygen index and mechanical properties of the modified PETs with ethylene tetrafluoroethylene copolymer (ETFE) and fully fluorinated ethylene propylene copolymer (FEP) would be the results by counterbalancing the fibrillation and nucleation of fluoropolymer.(3) The rheological measurement results showed that, the fluoropolymers underwent fibrillation during the shear processing of PET melts, and this led to the increase of apparent melt viscosity and thus the antidripping flame retardation would be improved to some extent.(4) The spinning and the dyeing experimental results showed that, the copolyester indicated good spinning performance. Both silica and ETFE improved the mechanical properties of partially orientated yarns (POY) and drawn texturing yarns (DTY) but the two deteriorated spinnability. Despite significantly improving the flame retardancy, coal aggravated spinnability of the copolyester as well. DTY and fully drawn yarn (FDY) from fPET produced mottling. After dosaging with silica, DTY yarn performed better dyeing ability with the ranking IV. The innovation points of this study are two:(1) The additives coal and Coal/APP flame retardant system were firstly employed to modify the thermal degradation, flame retardancy and charring of PET and fPET.(2) The effect of fluoropolymer PA5935 on thermal degradation and charring of fPET was firstly investigated, and the effects of the fluoropolymers on the mechanical properties and flame-retardancy of PET were carefully evaluated. Especially, the dispersion and mixing of the fluoropolymers in PET melt were interpreted based on the rheological mesurement.