Deformation Mechanism Of Dispersed Phase In PS/PP Melt Spinning

For the immiscible polymer blends, the properties of its products generally depend on the processing conditions and dispersed morphology. The mechanism of the dispersed phase deformation in the elastomeric polymer blends has been studied in Newton system and the types of flow mainly focus on the shearing flow. Recently, it has been generalized to elongation flow. There are very few literatures concerning the extensional deformation of dispersed phase during melt spinning, especially in the PS/PP blending system. This paper focuses on the rheological behaviors, interface interaction and blending viscosity ratio to analyze the mechanism of dispersed phase deformation. Besides, the preliminary exploration of temperature distribution along fiber’s radial direction has been done. Major research results as follow:First of all, the PS/PP blending fiber with gradient-structure was prepared by melt spinning with different viscosity ratios and take up speed. A new method for quick embedding, slicing and digital conversion of the SEM photos for blended fiber had been used for the characterization of fiber’s cross and vertical section. As a result, it is found that the dispersed phase distribute uniformly in the cross section of extrusive fiber without extension and the gradient degree of dispersed phase in PS/PP blending fiber increases not only with the take-up speed, but also with viscosity ratio. Besides, the coalescence of dispersed phase plays a important role when viscosity ratio and take-up speed increase which leads to a reduction of dispersed phase’s number and average diameter.Rheology behavior tests result shows that both of PP and PS are the extension-thinning fluid. The elongation flow activation energy had been calculated by Arrhenius formula, that shows the elongation flow activation energy of PS is much higher than that of PP on the same extensional deformation rate while the value of PS depends more on temperature under high deformation rate, but in case of PP, it is just the reverse.Base on the experienced theory, it is thought that the deformation and breaking of dispersed phase can be drew the conclusion by nonuniform distribution of the critical capillary number Cac, a dimensionless parameter, along both the fiber’s cross and vertical section that has been verified by both ID and2D model. In ID model which is independent of the radial temperature distribution, it is found that the critical capillary number Cac decrease with the growth of the distance to spinneret plate by comparing between extrusive fiber and take-up fiber. There is no breaking along the spinning line and the matrix-fibrillar morphology has been found in the SEM photograph obviously. In2D model which is controlled by the radial temperature distribution, it is found that both the critical capillary number Cac and the capillary number Ca by formula derivation is different along the fiber’s cross section, which accordingly leads to the different deformation of the dispersed phaseAccording to the theory of extensional deformation of dispersed phase under uniaxial elongation flow for Newton system proposed by Taylor, it can be calculated that are the deformation degree and its corresponding capillary number Ca in consideration of the interface tension. It is found that in every zone of cross section from core to the surface distributed by equal area, the deformation degree is increasingly small as well as the capillary number Ca. After sampling on spinning line, the cooling length has been proved to be0.6m and is much closed to0.58m which is calculated by theoretical equation. The deformation rate at solidification point is11.05s-1as the calculation based on the sampling on line. The fitting of radial temperature distribution and stress distribution profile are based on the relationship between the capillary number Ca and temperature as well as the calculated capillary number Ca. It is found that the temperature in centre is19.7K higher than that in surface and the radius is23.35μm. The radial temperature gradient in melt spinning fiber reaches to105K/m, which is acceptable compared with theoretical value.