Morphology of blends

Another example of static SIMS used in a more quantitative role is in the analysis of extmded polymer blends. The morphology of blended polymers processed by extrusion or molding can be affected by the melt temperature, and pressure, etc. The surface morphology can have an effect on the properties of the molded polymer. Adhesion, mechanical properties, and physical appearance are just a few properties affected by processing conditions. 

Fig. 61 a Schematic representation of phase diagram of blend of PS-rich (a) with Pi-rich (/S) PS-fc-PI block copolymer in parameter space of a, and T. Expected morphologies of blend specimen are also sketched at b low and c high temperatures. Note phase diagram is effective only for American Chemical Society... 

Journal of Applied Polymer Science 11, No.7, 15th Aug.2000, p. 1478-87 MORPHOLOGIES OF BLENDS OF ISOTACTIC POLYPROPYLENE AND ETHYLENE COPOLYMER BY RAPID EXPANSION OF SUPERCRITICAL SOLUTION AND ISOBARIC CRYSTALLIZATION FROM SUPERCRITICAL SOLUTION... 

The morphology of blends of asymmetric PS-Pl diblocks that do not form lamellar phases has been investigated using transmission electron microscopy by Koizumi et al. (1994c). They considered three cases (i) approximately equal... 

The time evolution of the morphologies of blends, solutions, dispersions and conventional block copolymers can be modeled by dynamic simulations. The different length and time scales... 

Abe H, Doi Y, Kumagai Y (1994a) Synthesis and characterization of poly[(R,S)-3-hydroxybu-tyrate-b-6-hydroxyhexanoate] as a compatibilizer for a biodegradable blend of poly[(R)-3-hydroxybutyrate] and poly(6-hydroxyhexanoate). Macromolecules 27 6012-6017 Abe H, Dd Y, Satkowski MM, Noda I (1994b) Miscibility and morphology of blends of isotactic and atactic poly(3-hydroxybutyrate). Macromolecules 27 50-54 Abe H, Matsubara I, Doi Y (1995) Physical properties and enzymic degradability of polymer blends of bacterial poly[(R)-3-hydroxybutyrate] and poly [(R,S)-3-hydroxybuty rate] stereoisomers. Macromolecules 28 844-853... 

The morphology of blends with more than c, 67 mass% COP is almost indistinguishable from that of pure COP independent of whether pressure was applied or not. 

The miscibility and morphology of blends of poly(3-hydroxybut-yrate) (PHB) and PVB was studied by differential scanning calorimetry (DSC) and scanning electron microscope (SEM) (22). 

A number of novel approaches have been developed to provide improved morphological control. One approach has been to create polymer nanoparticles of well-defined size via a miniemulsion process (see Figure 14.9) [56, 57]. Films are prepared from an aqueous dispersion containing polymer nanoparticles. Separate donor and acceptor nanoparticles can be prepared and then blended, or nanopar-tides can be prepared where both donor and acceptor polymers are contained in each nanoparticle. In both cases, the upper limit for the dimension of phase separation is determined by the size of the individual nanoparticles. A limitation of this approach is that the smallest size nanoparticles that can be produced (a few tens of nanometers [57]) already have sizes larger than the exciton diffusion length, and the morphology of blended nanospheres tends to adopt a core-shell structure that may not be ideal for device operation [58]. 

Tanaka and Nishi (1985) were the first to report about the existence of coupling between crystallization and demixing in crystallizable blends. A competition between demixing and crystallization is seen in binary blends of a semicrystalline and an amorphous polymer when the crystallization curve and the miscibility gap intersect. The morphology of blends exhibiting such behavior is determined by the ratio of the rate of crystallization and of demixing. Four important situations can be distinguished (Fig. 3.41) ... 

The morphology of blends may be complex. The addition of compatibilizer not only affects the size and shape of the separated phases (the macromorphology), but it may also affect the crystalline form, the size of crystalline entities, as well as the total crystallinity (the micromorphology). In a blend of two semicrystalline polymers, e.g., PE/PP, four phases may coexist ... 

Isayev and Modic (1987b) reported that injection molded and extruded blends of an HB A/HNA LCP and PC containing greater than 25 wt% LCP had spherical LCP domains dispersed in the PC matrix. However, blends with 10 % LCP had a fibrillar morphology. Pracella et al. (1987) reported a similar observation when they examined the morphology of blends of PBT with another LCP. The fracture surfaces of blends that contain up to 50 wt% LCP revealed the presence of rod-like structures of the LCP component oriented perpendicular to the fracture plane. For blends that contain more than 50 wt% LCP, the morphology was homogeneous and LCP domains were not observed. 

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