P-spherulite

Figure 1 Two different views of immature p-spherulites by SEM (a) face-like (in centre) and flower-cup like left bottom) ones (b) the flower-cup like array at a higher magnification.

Figure 1 Microstructure of the whole cross-section of a thick section iPP molding exhibiting a and p spherulites.

These concepts have to be correlated with the inherent helical form of the starch molecule, and attempts which have been made to determine the orientation of the portions of the molecules in the crystallites will be dealt with later (in the Section on x-ray diffraction studies—see p. 376). In this connection, the work on the orientation of synthetic crystalline polymers into spherulites containing helically arranged molecules23 may be important. 

Johannsenite, Ca(Mn,Fe )Si206, is a species in whieh p = 0. There is little additional trivalent ion (Al, Fe, or Cr ) substitution. The mineral is most commonly found as spherulitic aggregates of brittle fibers or prisms. Another pyroxene, acmite (NaFe Si206), has been found as large (100 X 35 X 20 cm) single crystals of prismatic shape, as needles, as felted aggregates of fine fibers, and as capillary crystals. 

Figure 5.7. Optical microscope image of a thin film (thickness 2 p.m) of a-p-NPNN grown on a glass substrate (1.6 x 1.0 mm, crossed polarizers). Reprinted from Journal of Crystal Growth, Vol. 209, J. Caro, J. Fraxedas and A. Figueras, Thickness-dependent spherulitic growth observed in thin films of the molecular organic radical p-nitrophenyl nitronyl nitroxide, 146-158, Copyright (2000), with permission from Elsevier.

Figure 6.103 Schematic of Maltese cross produced by spherulites in crosspolarized filters. Reprinted, by permission, from Strobl, G., The Physics of Polymers, 2nd ed., p. 146. Copyright 1997 Springer-Verlag.

Figure 8.4. Forms of polycrystalline aggregate (a) botryoidal (b) mamillary (c) spherulitic (d) oolitic (see p. 156).

Carr, S. H., Geil, P. H., Baer, E. The development of spherulites from structural units in glassy poly(bisphenol-A-carbonate). J. Macromol. Sci.-Phys. B2,13-28 (1968). 

Adamski, P. and Czyzewski, R. Activation energy and growth rate of spherulites of cholesterol liquid crystals. Soc. Phys. Crystallogr. 23, 725 (1978)... 

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