Study On Stabilization Extrusion And Chain Extension Of PET Flakes

The effect of different extruders on the chain extension of PET and the fluctuation of melt pressure with polyethylene terephthalate as raw material in different technological conditions was studied in this thesis.The experimental results indicated that the intrinsic viscosity ([η]) of commercial PET Flakes was different, the [η] of green Flakes was0.72dl/g, and the [η] of white Flakes was0.78dl/g.Experiments on the reactive extruder of type30with the BM separation element in the middle of screw, it was found that the vacuum degree of polycondcnsation could only reach up to0.08-0.09MPa, the vacuum gauge and the melt pressure in the head of screw fluctuated seriously, and the speed of discharging was sometimes fast and sometimes slow.The optimum technological condition is:the barrel temperature of the extruder is245,255,250,250,240℃(the die), the screw speed is60rpm, the vacuum degree of polycondensation is0.09MPa, and the extrusion product is transparen.The experimental result showed that the pyromellitic dianhydride (PMDA) was a good chain extender for PET Flakes; in the dosage range of0.35%, the intrinsic viscosity of extrusion was increased obviously with the increase of the content of PMDA and could reach up to0.85dl/g; the extrusion product was gelatinous and became darker in color when the PMDA content was over0.35%.Experiments on the reactive extruder of type35with the Maddock mixing element in the middle and head of screw, it was found that the extruder ran smoothly, there were no noises, the vacuum degree of polycondensation could reach up to0.10MPa, and the vacuum gauge fluctuated hardly.The optimum technological condition of the reactive extruder of type35is: the barrel temperature of the extruder is245,260,260,250,240℃(the die), the vacuum degree of polycondensation is0.10MPa, and the screw speed is40rpm; under that condition, the intrinsic viscosity of extrusion is0.68dl/g.By rubbing the Maddock mixing element in the head of the reactive extruder of type35, the output of the extruder was raised to30percent, and there was no discharge of polycondensation. The fluctuation of melt pressure in the head of screw was gentle, and the product quality was satisfied with the demand of extrusion moulding. Experiments on the improved reactive extruder of type35, the intrinsic viscosity of extrusion reached up to0.91dl/g and the average of melt pressure was raised to125%when the PMDA content was0.3%wt. The fluctuation of melt pressure in the head of screw was gentle, and the product quality was satisfied with the demand of extrusion moulding.