Polypropylene isotactic cross-hatching

Fig. 3.21 Tapping mode AFM phase image left) and height image right) of cross-hatched lamellae of iPP in elastomeric polypropylene and isotactic PP, respectively. The angles of 80° agree well with the theoretically predicted and experimentally confirmed value [53]. Reproduced with permission from [51]. Copyright 2002. American Chemical Society, and [54]...

Fig. 15. Two views of early growth at 155°C in isotactic polypropylene (monoclinic structure). One object would appear cross-hatched in plan (above) or sheaf-like when viewed sideways (below). Replica of an etched cut...

Fig. 2.5 Morphological effects of the recrystallization of isotactic polypropylene at 145 °C (a) radial growth enclosing a leaf-shaped area of cross-hatched material, (b) a similar area after partial melting (From figure 4 in. Weng J, Olley RH, Bassett DC and Jaaskelainen P, Changes in the Melting Behavior with the Radial Distance in Isotactic Polypropylene Spherulites. J. Polym. Sd. Polym. Phys. 41 2342-2354. Copyright 2003 by John Wiley Sons, hic. Reprinted by permissirai of John Wiley Sons, Inc.)...

Auriemma F, De Rosa C (2006) Stretching isotactic polypropylene from cross-p to cross-hatches, from a form to y form. Macromolecules 39(22) 7635-7647 Baird DG (1998) Polymer processing principles and design. Wiley-Interscience, New York Bassett DC, Olley RH (1984) On the lamellar morphology of isotactic polypropylene spherulites. Polymer 25(7) 935-943... 

Secondary crystallization in isotactic polypropylene occurs in a peculiar way. On cooling additional crystallites are formed, however, many of them are oriented oblique to the primary lamellae rather than p lrallel as is normally observed. As explained by Lotz and Wittmann [8], this cross-hatching is caused by an epitaxial growth mechanism. If cross-hatching occurs the one-dimensional model used so far in the analysis of SAXS data becomes invalid. There is a simple check which shows the deviations. For a stack of crystallites one expects... 

Additional details of the structure of semicrystalline polymers can be determined on such selectively etched surfaces. SEM micrographs in Figure 3.9 show the two main types of isotactic polypropylene (PP) Micrograph (a) shows the most common a-modification with the so-called cross-hatched... 

Lamellar habit is also known for crystallization from the melt under isothermal and nonisothermal conditions. Typical views of lamellae in isotactic polypropylene or isotactic sequences in elastomeric polypropylene are shown in Figure 6.15, also for comparison with data discussed in Chapter 3. The typical cross-hatched morphology with angles of 80° agrees well with the theoretically predicted and experimentally confirmed value [26]. Independent of the AFM mode (contact mode, intermittent contact mode, pulsed force mode) consistent observations were made. 

Figure 33 Isotactic polypropylene crystallized from the melt at 150°C, showing cross-hatching...

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