The Theoretical And Experimental Studies On Fiber Forming And Structure Contral Of One-Step POY/FDY Polyester Differential-Shrikage Combined Yarn

One-step POY (Pre-oriented Yarn)/FDY (Fully Draw Yarn) polyester differential-shrinkage combined yarn has a good elasticity and bulkiness, which is widely used in wool-like, silk-like and high-grade knitted fabrics with a good market prospect. However, systematic experimental and theoretical studies are penurious in technical problems about the manufacturing and aggregation structure control of one-step POY/FDY polyester differential-shrinkage combined yarn.In this paper, we have focused on the manufacturing of one-step POY/FDY polyester differential-shrinkage combined yarn and systematically studied the evolutions of the diameter, tension, birefringence and crystallinity of POY and FDY from the spinneret hole to the composite point. We have established the quantitative relationship between the manufacture process parameters of melt-spinning, drawing and heat-setting process and the fiber tension and internal structure, from which the theoretical basis is provided to the manufacture and differential-shrinkage control of one-step POY/FDY polyester differential-shrinkage combined yarn. At the same time,72dtex/50f one-step POY/FDY polyester differential-shrinkage combined yarn has been manufactured on the one-step equipment, and the contrast is made between the theoretical and experimental results of the diameter, tension, birefringence and crystallinity of POY and FDY.In this paper, four main aspects are included:(1) The mathematical model of melt spinning of one-step POY/FDY polyester combined yarn was established and the evolutions of the diameter, tension, velocity, temperature, birefringence and crystallinity of POY and FDY on the spinning process are simulated. It is founded that the diameter, tension, temperature and velocity of POY changed more violently than those of FDY. POY can form a good degree of crystallinity and orientation which can be up to 16% and 0.085 separately, while those of FDY can be neglected; the influence of the variation of POY and FDY's pump capacity and spinning velocity on fiber tension, birefringence and crystallinity was studied: with the growth of spinning velocity and the decrease of pump capacity, POY and FDY's tension, birefringence and crystallinity became bigger and bigger.(2) The mathematical model of drawing process of FDY fiber in one-step POY/FDY polyester combined yarn has been established. Based on the existing parameters of FDY drawing process, we have studied the neck-deformation and the evolution of the fiber kinematics and dynamics parameters (strain, velocity, stress and strain rate), stress-strain curve and structure parameters (crystallinity and the degree of orientation) in the drawing process, and also have investigated the effect of the different draw ration on the fiber neck-deformation point, strain, velocity, stress, birefringence and crystallinity:with the growth of the draw ratio, the neck-deformation point, the strain-harden point and the point of becoming steady velocity and stress shift upstream to GR1, and the stress, crystallinity and birefringence have become bigger and bigger. (3) The mathematical model of annealing process of FDY fiber has been established. We have investigated the effect of the different temperature of GR2 and different draw ratio on the crystallinity's evolution of FDY fiber. The results are founded that with the growth of the temperature of GR2, the crystallinity of FDY becomes bigger, and with the growth of the draw ratio, the crystallinity and crystallinity rate become higher. Also there is no significant difference between the theoretical and experiential results.(4) We have researched the choice of process parameters for 72dtex/50f one-step POY/FDY polyester differential-shrinkage combined yarn in the actual manufacture process, and determined the parameters of pre-crystallization, evaporation, melting, spinning components, quenching, cluster point, drawing and winding. The diameter, tension, birefringence and crystallinity of POY and FDY have been tested, and it is founded that there is no significant difference when compared to the theoretical results. So it is reasonable to use the theoretical model to guide the actual manufacture.