Study On Spinnability Of Polyethylene Terephthalate Microfilaments Pre-oriented Yarn By Direct Melt Spinning

Evaluation of spinnability is the comprehensive performance evaluation of meltpolyethylene terephthalate (PET) and pre-oriented yarn (POY) on processingperformance. The basis for the evaluation in this work is the production stability andproduct quality. For the development of microfilament POY75dtex/144f and productionoptimization, the relations between the average molecular weight, molecular weightdistribution, the carboxyl end group content, rheological properties and crystallizationproperties and spinnability of PET were studied. In addition, the operating parametersincluding the annealing temperature, cooling method and collection oiling point werestudied too. The results showed that:1．When the carboxyl end group content of Luoyang PET device was in the rangeof30-34mol/t, the PET degradation degree became weak and thus the spinnability ofmelt PET was significantly improved.2．The chips that used to spin fine denier POY, compared to that used to spinordinary POY, has the following characteristics: the average molecular weight wasrelatively higher (up to23000Dalton), the molecular weight distribution was relativelynarrower; the crystallization degree of the chip was as low as about3.1%; in the processof PET melt cooling, the melt crystallization temperature and the melt crystallizationenthalpy were relatively higher, the crystallization rate was faster under highertemperatures; the rheological properties of PET exhibited higher apparent shearingviscosity and lower apparent extensional viscosity under higher extensional stress.3. Annealing temperature obviously affected the crystallization properties of thefibers. With the increase of annealing temperatures, the cold crystallization temperatureof the fibers decreased, the cold crystallization enthalpy of the fibers decreased and thecrystallization degree of the fibers increased. When the annealing temperature increasedfrom320oC to330oC, the irregularity uniformity of the samples was improved and thestrength and modulus of the samples were reduced. The gas pressure was one of the mainfactors affecting the irregularity uniformity of the fibers. The fibers has the smallestirregularity CV value under a specific circular quench pressure.4. Circular quench is helpful to improve the irregularity uniformity and themechanical properties of the fibers. Compared with side quench, crystallization degree ofPOY produced under circular quench increased by at least3%.5. The optimal operating parameters for the production of POY75dtex/144weredetermined as follows: circular quench pressure80Pa, collection oiling position86cm,annealing temperature330oC. When the POY produced under the above conditions were used to produce draw textured yarn (DTY), the resultant DTY product showed qualifiedmechanical strength and no hair silk was found.