Spherulites polystyrene

Figure 8.1. (a) Spherulites growing in a thin film of isotactic polystyrene, seen by optical microscopy with crossed polars (from Bassett 1981, after Keith 196.3). (b) A common sequence of forms leading to sphertililic growth (after Bassett 1981). The fibres consist of zigzag polymer chains. 

Figure 10.5 shows scanning electron micrographs of blend samples that were prepared as described in the Experimental Section . The etchant preferentially attacks polyethylene, producing a topography in which the polystyrene-rich domains are raised above the polyethylene domains. The interlamellar amorphous material provides a location for styrene to penetrate and polymerize. A considerable amount of polystyrene is present in the center of the spherulites. This is due either to amorphous polyethylene that is present in these locations or to voids that develop during crystallization... 

Figure 2.8 Spherulite of isotactic polystyrene crystallized from the melt. (From Ref. 8.)...

The morphology of crystalline isotactic polystyrene, i-PS, has been investigated by others, and they have concluded that i-PS normally crystallizes as stacks of folded chain lamellae which are arranged in volume filling spherulites. The melting point of lamellar polymer crystals depends on the lamella thickness, L, as follows (28 )... 

FIGURE 11.1 Radial growth rate r of spherulites of isotactic polystyrene as a function of the crystallization temperature. 

Films from nitromethane also exhibited rather perfect spherulites of PEO, which contained globules of the insoluble PS (Figure 6.5). On the other hand, films from chloroform, which, being a good solvent for both components, permits more efficient organization during drying, show spherulites in which the fibrils appear to be coated more or less uniformly with polystyrene. 

Figure 5.8 Micrograph of isotactic polystyrene crystallized at 200 °C showing sheaflike spherulites. ...

Figure 4.20 Plots of growth rate of the spherulite versus degree of undercooling, AT, under isothermal conditions [38). (a) Isotactic polystyrene (b) nylon 6 (c) polyoxypropy-lene (d) polychlorotrifluoroethylene...

Polypropylene and Polystyrene. As with PE, afm has yielded important structural details for the different grades of polypropylene (PP) and Polystyrene (PS). Syndiotactic polystyrene (sPS) was imaged (Fig. 12), showing a spherulitic... 

Early results with cryomicrotomes were described by Cobbold and Mendelson [80]. Polyurethane elastomer, a blend of crystalline and noncrystalline polymers, showed spherulitic textures after sectioning at about -70°C. Injection molded polypropylene (PP) was also sectioned at about -70°C, while polytetrafluoroethylene (PTFE) was sectioned at much lower temperatures. The authors concluded that the technique, though difficult, had potential. Extruded styrene-butadiene-styrene (SBS) copolymer was prepared by cryosectioning with a diamond knife in liquid air at —85 to —115°C, followed by osmium tetroxide vapor staining for one hour [81]. This method revealed the alternating sequence of the polystyrene and polybutadiene lamellae. Odell et al. [82] prepared extruded triblock copolymer by first chemically hardening the polybutadiene, with osmium tetroxide, followed by cryoultramicrotomy to produce 30 nm thick sections which showed fine structure details. Parallel polystyrene rods were observed in the SBS copolymer. Ultramicrotomy and selective staining with osmium tetroxide was also used in the preparation of a binary blend of PP and thermoplastic rubber [83]. 

Figure 6.22 (66) illustrates the spherulite morphology for poly(ethy-lene oxide)-h/oc -polystyrene. Two points should be made. First, the glass... 

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