Study On Morphology And Distribution Of Dispersed Phase In PP/PS Blends Under Shear Flow

The morphology of dispersed phase in blend fibers is an important factor which can directlyaffect the performance of the fibers, and numerous studies have focused on the morphology andgraded structure of dispersed phase in take-up fibers. Melt-spun process includes shear flow inspinneret holes and elongational flow after melt extruding, but the effect of shear flow in spinneretholes on dispersed phase morphology has rarely been reported. Study on the morphology anddistribution of dispersed phase in blends under shear flow can enrich the research on gradedstructure in blend fibers and provide basic guidance for molding process which involves shearflow. Based on the former results of our research group, this paper uses capillary rheometer and anew sampling method to get extrusion spline which only experienced shear force. With the help ofSEM and digital characterization methods, it was successfully investigated that the morphologyand distribution of dispersed phase in PP/PS blends under shear flow. By adjusting shear rate,blend ratio and viscosity ratio, the influencing factors of dispersed phase morphology have beendiscussed.The main research contents and conclusions are summarized as below:(1) The preparation and sampling of PP/PS blend spline. Using capillary rheometer, the blendsplines were prepared with shear rate2000s-1,4000s-1,5000s-1and8000s-1, PS contents4wt.%,6wt.%and8wt.%, viscosity ratio5.2,9.2and16.6, respectively.(2) The characterization method of dispersed phase morphology. After resin embedding,frozen ultrathin slicing and etching, the morphology of dispersed phase was observed by SEM.Using digital characterization methods to gain the information of dispersed phase morphology anddistribution, it was studied that the effect of shear force on the number, diameter, aspect ratio and volume of dispersed phase.(3) The morphology and distribution of dispersed phase in shear flow. With the increasing ofshear rate, the average diameter and volume of dispersed phase decreases, the aspect ratio andnumber increases. In addition, the diameter, aspect ratio and volume increases along the radicaldirection, but the number decreases. When the content of dispersed phase increases, coalescenceoccurs, as a result, the diameter, volume and number increases, only aspect ratio decreases, alongthe radical direction, that is the same as the effect of shear rate. As for blend viscosity ratio, thediameter becomes smaller when viscosity decreases, that means the lower the viscosity ratio is,the smaller the dispersed phase will be.