Formation Mechanism Of Surface Structure Of Polyester/Polyamide 6 Blend Fiber

The surface properties of polymer blends are inextricably linked to surface structure,and the surface structure depends on the evolution of the dispersed phase morphology formed by the processing method and processing technology.The morphology of the dispersed phase has always been one of the research hotspots in the blend polymer system.At present,the control methods of polymer surface structure include laser treatment,phase separation,plasma treatment,etc.Most of these methods have the disadvantages of high cost,complicated processing,and small processing scale,which cannot satisfy large-scale industrialized production.Therefore,the melt blending method has become a commonly used method for regulating the surface structure of polymers due to its advantages of simple process and large processing scale.This paper takes polyester(PET)and polyamide 6(PA6)as the research objects,a series of PET/PA6 blended fibers with rough surface structure were prepared by adjusting the raw material component ratio and the drawing ratio of the spinning process by the melt blending spinning method.By exploring the rheological properties and interfacial properties of raw materials,analyzing the microrheological behavior of the dispersed phase inside fibers,and based on the spinning kinetics,the formation mechanism of the surface structure of PET/PA6 blended fibers was studied.This paper develops work in the following aspects and draws conclusions:(1)Firstly,the rheological properties of the raw polymer and the interfacial tension of the system were studied.The rheological properties of the raw materials were studied by rotational rheometer and capillary rheometer,it was found that the shear viscosity and extensional viscosity of PET and PA6 both showed shear thinning phenomenon,and the viscosity of PET was higher than that of PA6.By calculating the viscous flow activation energy at different tensile strain rates,it was found that the viscous flow activation energy of the two polymers decreases with the increase of the tensile strain rate,and the viscous flow activation energy of PET was higher than that of PA6,showing a higher temperature dependence than PA6,and both polymers are less sensitive to temperature at high tensile strain rates.The interfacial tension of PET/PA6 blends was studied by using the deformed droplet-embedded fiber retraction measurement method,the interfacial tension was found to decrease linearly with increasing temperature,the fitting equation that can be used to calculate the interfacial tension of the system at different temperatures isσ=74.93-0.243 T.By using the Wu equation,the interfacial bonding work of the system was calculated,it was found that the interfacial bonding work increased with the increase of temperature,it showed that the interfacial adhesion of the non-blended system at high temperature was better than that at low temperature,the spinning temperature has a great influence on the compatibility of the system.(2)Then the effects of component ratio and stretching ratio on the morphology evolution of the dispersed phase along the radial direction and on the surface structure were explored.The cross-sections of gravity yarns and winding yarns obtained by melt spinning were characterized by image binarization analysis and processing method,it was found that the dispersed phase inside the blended fiber developed from an ellipsoid to a microfibril shape after stretching,the dispersed phase presents an uneven distribution of "dense inside and sparse outside,large inside and small outside" along the radial direction of the fiber.And this distribution was more obvious after stretching,The morphology evolution of the dispersed phase was mainly concentrated in the uniaxial extensional flow field after exiting the spinneret hole.The surface structure of the blended fiber observed by SEM,it was found that the convex structure on the surface of the gravity filament develops more obviously with the increase of the component ratio,the structure was formed by the coalescence and deformation of the dispersed phase;The width and quantity of groove structures on the surface of the coiled wire intuitively increase with the increase of the size and number of internal dispersed phases.With the increase of composition ratio and stretch ratio,the interface separation degree of the system increases.The groove structure was formed by the convex structure on the surface of the gravity filament through the interface separation and depression after the tensile stress of the spinning process.(3)Finally,the deformation process of the blended fiber along the spinning process was simulated.By using melt spinning dynamics to simulate changes in temperature,speed and tensile strain rate on the spinning process,it was found that along the spinning process,the temperature gradually dropped to room temperature,when the speed rised rapidly to the set value of spinning speed,the tensile strain rate first increased and then decreased,the temperature and tensile strain rate directly affected the change of the viscosity of the system on the spinning process,and then affected the evolution of the dispersed phase.Based on the Delaby droplet deformation theory,the degree of deformation of the dispersed phase along the spinning process was calculated,and the simulated value of the radius of the dispersed phase was compared with the measured value,it was found that the degree of deformation of the dispersed phase increased rapidly and then remained unchanged,the simulated value of dispersed phase radius was close to the measured value,it showed that the deformation simulation can predict the deformation of spun blended fibers.Based on the research system and results of this paper,a judgment hypothesis for the occurrence of groove structure in PET/PA6 blend fiber was proposed,which is used to determine the critical point of groove structure.