| In this study the effect of flow through a capillary die on the surface properties and morphology of a polymer blend was investigated. Previously, it was shown that mixing a “hyperbranched polymer”, or HBP, with a linear polymer resulted in an increase in the apparent shear rate for a given shear stress, when compared to the virgin polymer. The postulate is that the HBP acts as a processing aid, whose viability may be influenced by the capillary length.; The hypothesis is that the two polymers form an immiscible mixture and a thin HBP layer near the fiber surface accounts for the increase in the apparent shear rate. Thus, it is important to examine phase separation as a function of capillary length to determine if a diffusive mechanism is present. Polymer samples were extruded through a 30 mm length capillary die and a zero-length capillary, or orifice plate; both the capillary and the orifice plate were 1.5 mm in diameter. A DSC study was performed to determine the effect of temperature and HBP concentration on phase separation. The extruded polymer samples were viewed in TEM to visualize the layers.; The results show that the shear rate increase does exist and that the HBPs and the virgin polymer do phase separate and that the HBP migrates to the surface as hypothesized. Further, capillary length influences the morphology, although the exact diffusive mechanism is unclear. |
