ABSTRACT
FIGURE 5.1 Scanning electron microscopy (SEM) photomicrograph (2000× magnication) of cryofracture surface of polypropylene/polystyrene (PP/PS) blends. Another view of cylinder-like structure of polystyrene minor phase in melt-blended 70 wt% polypropylene/30 wt% polystyrene blends. This image illustrates clearly the extent of ow-induced orientation during the process of melt-extrusion. Note that some spherical particles coexist with the overall oriented structure. These can originate from breakup of ne cylinders (bers). (From T. S. Omonov, Crucial Aspects of Phase Morphology Generation and Stabilization in Two-and Three-Phase Polymer Blends: Physical, Reactive and Combined Routes of Compatibilization, Ph.D. thesis, Katholieke Universiteit Leuven, Belgium, 2007, under the supervision of C. Harrats and G. Groeninckx.)
FIGURE 5.2 SEM photomicrograph (2000× magnication) showing highly oriented structure in melt-blended polypropylene/polystyrene blends. Cryofracture surfaces. This is an additional example of anisotropic phase morphology in 70 wt% polypropylene/30 wt% polystyrene blends. The elongated entities of the minor phase (30 wt% polystyrene) are clearly visible in the matrix (70 wt% polypropylene). They are cylinders of innite length as a result of extensive orientation in the die entrance during the extrusion process. Structure observed in the longitudinal direction with respect to the extrusion axis. (From T. S. Omonov, Crucial Aspects of Phase Morphology Generation and Stabilization in Two-and Three-Phase Polymer Blends: Physical, Reactive and Combined Routes of Compatibilization, Ph.D. thesis, Katholieke Universiteit Leuven, Belgium, 2007, under the supervision of C. Harrats and G. Groeninckx.)
FIGURE 5.3 SEM photomicrograph (1000× magnication) of cryofracture surface of 60 wt% polypropylene/40 wt% polystyrene. This image reveals that the cylinders are getting more in contact and the overall structure contains more at structures, indicating the formation of a sheet-like minor phase structure. Four-way branches are clearly visible. (From T. S. Omonov, Crucial Aspects of Phase Morphology Generation and Stabilization in Two-and Three-Phase Polymer Blends: Physical, Reactive and Combined Routes of Compatibilization, Ph.D. thesis, Katholieke Universiteit Leuven, Belgium, 2007, under the supervision of C. Harrats and G. Groeninckx.)
FIGURE 5.4 SEM photomicrograph of melt-blended 50 wt% polypropylene/50 wt% polystyrene blend extruded at a mixing temperature of 215°C. The PS and PP homopolymers are fed into the extruder after dry blending under nitrogen ux. The major component is introduced under nitrogen ux at a screw rotation speed of 50 rpm. As the drymixed components are completely fed into the extruder, the screw rotation speed is increased to 100 rpm and the blending continued for 10 min. This image illustrates how crucial is the direction and plane of observation in anisotropic phase morphologies. In this case the surface observed was broken longitudinal to the extrusion axis where the minor phase particles have been substantially elongated into elongated at tape structures. (From T. S. Omonov, Crucial Aspects of Phase Morphology Generation and Stabilization in Two-and Three-Phase Polymer Blends: Physical, Reactive and Combined Routes of Compatibilization, Ph.D. thesis, Katholieke Universiteit Leuven, Belgium, 2007, under the supervision of C. Harrats and G. Groeninckx.)
FIGURE 5.5 SEM photomicrograph of a cryofracture surface of the same sample in Figure 5.4 showing the transition between cylinder-like structure and at sheet-like structure formation. This is, of course, due to the composition effect. The content of the minor polystyrene phase is higher compared to Figure 5.1 through Figure 5.3. (From T. S. Omonov, Crucial Aspects of Phase Morphology Generation and Stabilization in Two-and Three-Phase Polymer Blends: Physical, Reactive and Combined Routes of Compatibilization, Ph.D. thesis, Katholieke Universiteit Leuven, Belgium, 2007, under the supervision of C. Harrats and G. Groeninckx.)
FIGURE 5.6 A much more illustrative SEM photomicrograph showing the interconnection of the matrix and the minor phase-oriented, sheet-like structure in melt-blended 40 wt% polypropylene/60 wt% polystyrene blends. (From T. S. Omonov, Crucial Aspects of Phase Morphology Generation and Stabilization in Two-and Three-Phase Polymer Blends: Physical, Reactive and Combined Routes of Compatibilization, Ph.D. thesis, Katholieke Universiteit Leuven, Belgium, 2007, under the supervision of C. Harrats and G. Groeninckx.)
FIGURE 5.7 SEM photomicrograph (1000× magnication) of cryofracture surfaces of 30 wt% polypropylene/70 wt% polystyrene blend. The image shows another type of sheet-like cocontinuous phase morphology where the minor phase appears as sheets highly oriented in the direction of extrusion. This composition is the opposite of the samples shown in Figure 5.1 and Figure 5.2. When the polypropylene is the minor phase, it does not exhibit cylinder-like structures but at, sheet-like entities, interconnected to form a continuum in the polystyrene matrix. (From T. S. Omonov, Crucial Aspects of Phase Morphology Generation and Stabilization in Two-and Three-Phase Polymer Blends: Physical, Reactive and Combined Routes of Compatibilization, Ph.D. thesis, Katholieke Universiteit Leuven, Belgium, 2007, under the supervision of C. Harrats and G. Groeninckx.)
FIGURE 5.8 SEM photomicrograph (2000× magnication) of the same sample as in Figure 5.7. The image shows more details on a smaller area of observation. Note that the visible particles constitute the grafting zones by which cocontinuity is ensured over the whole blend volume. (From T. S. Omonov, Crucial Aspects of Phase Morphology Generation and Stabilization in Two-and Three-Phase Polymer Blends: Physical, Reactive and Combined Routes of Compatibilization, Ph.D. thesis, Katholieke Universiteit Leuven, Belgium, 2007, under the supervision of C. Harrats and G. Groeninckx.)
FIGURE 5.9 SEM photomicrograph of cryosmoothed and chloroform-etched surfaces of melt-blended 30 wt% of polypropylene/70 wt% polystyrene blend. This image shows complex phase morphology, although it appears simply as a common cocontinuous. A close observation inside the voids, which are the empty spaces left after the selective extraction of the polystyrene phase, reveals that the morphology of polypropylene is composed of two structures: a major continuous and tortuous phase in which are attached grape-like particles of the same phase (polypropylene). This phenomenon is quite expected, as the content of polypropylene is only 30 wt%, which makes it more vulnerable to extension and breakup. These particles remain attached as shown to the mother phase of polypropylene, which constitutes the major part of the network after the etching of the polystyrene phase. (From T. S. Omonov, Crucial Aspects of Phase Morphology Generation and Stabilization in Two-and Three-Phase Polymer Blends: Physical, Reactive and Combined Routes of Compatibilization, Ph.D. thesis, Katholieke Universiteit Leuven, Belgium, 2007, under the supervision of C. Harrats and G. Groeninckx.)
FIGURE 5.10 SEM photomicrograph (4000× magnication) of the same sample as in Figure 5.9, but the scale of observation is much smaller. The image shows clearly how the particles are organized in grapes that are attached to the polypropylene mother phase. If they were loose, they would be extracted as solid suspensions with the solvent of polystyrene during the etching process. (From T. S. Omonov, Crucial Aspects of Phase Morphology Generation and Stabilization in Two-and Three-Phase Polymer Blends: Physical, Reactive and Combined Routes of Compatibilization, Ph.D. thesis, Katholieke Universiteit Leuven, Belgium, 2007, under the supervision of C. Harrats and G. Groeninckx.)
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