Phase Morphology and Orientation Development of Polymer Blends in Melt Processing
In this dissertation, we studied phase morphology development of various polymer blends in both extrusion and melt spinning using scanning electron microscopy (SEM) assisted with appropriate etching techniques. Various processing conditions, for example shear or elongation rate, shear or elongation stress, and extrusion die length / diameter ratio were considered. The effects of material characteristics, such as viscosity ratio, miscibility and interfacial tension, were studied. To do this, polymer blends were carefully selected. One isotactic polypropylene was blended with two ethylene butene copolymers (EBM), which had different butene contents. One of the blends was miscible and the other was immiscible. The polypropylene was also blended two ethylene octene copolymers (EOM). The above blends had low interfacial tension and different viscosity ratios. One EBM was blended with two polyamide 12 (PA12) materials. These blends had high interfacial tension and different viscosity ratios. One maleic anhydride grafted ethylene octene copolymer was added into the EBM / PA12 blends to decrease their interfacial tension. Studies were focused on a phenomenon that the dispersed phases in these blends could coalesce into a surface layer in both extrusion and melt spinning. This process was controlled by viscosity ratio, interfacial tension and processing conditions. The orientation development of melt spun fibers of these blends was studied by both wide angle X-ray diffraction (WAXD) and birefringence techniques. The orientation was affected by both blend morphologies and solidification order of the blend individual phases. The phase, which solidifies later in the spinline, did not affect the orientation of the first solidified phase. However, the first solidified phase, if it was continuous phase, could largely suppress the orientation of the second solidified phase. Composite stress analysis explained the different orientation behaviors. Extrusion of a PA12 material through a capillary die coated with a EBM material was studied. The EBM coated die could largely increase the flow rates of the PA12 melt compared with a clean die. This behavior was explained by significant interface slippage between PA12 and EBM melts. A flow model was given to calculate the slippage speeds. Adding some maleic anhydride grafted ethylene octene copolymer into the EBM could largely suppress the interface slippage between PA12 and EBM.
School:The University of Akron
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:polypropylene ethylene butene copolymer octene polyamide 12 blend phase morphology orientation birefringence extrusion melt spinning coalescence slippage
Date of Publication:01/01/2008