Spherulites development

A system of mutually impinging spherulites develop into an array of irregular polyhedra, the dimensions of which can be as large as a centimeter or so. 

Recent developments have allowed atomic force microscopic (AFM) studies to follow the course of spherulite development and the internal lamellar structures as the spherulite evolves [206-209]. The major steps in spherulite formation were followed by AFM for poly(bisphenol) A octane ether [210,211] and more recently, as seen in the example of Figure 12 for a propylene 1-hexene copolymer [212] with 20 mol% comonomer. Accommodation of significant content of 1-hexene in the lattice allows formation and propagation of sheaf-like lamellar structure in this copolymer. The onset of sheave formation is clearly discerned in the micrographs of Figure 12 after crystallization for 10 h. Branching and development of the sheave are shown at later times. The direct observation of sheave and spherulitic formation by AFM supports the major features that have been deduced from transmission electron and optical microscopy. The fibrous internal spherulite structure could be directly observed by AFM. 

Abstract The morphology of polyethylene has been an important theme in polymer science for more than 50 years. This review provides an historical background and presents the important findings on five specialised topics the crystal thickness, the nature of the fold surface, the lateral habit of the crystals, how the spherulite develops from the crystal lamellae, and multi-component crystallisation and segregation of low molar mass and branched species. 

At higher crystallisation temperatures (regime C(II)) spherulites developed droplets of PS-rich material at their growth surfaces (Fig. 62) according to Tanaka and Nishi [146] a small gap existed between the droplets and growth surfaces in the early stages (1860 min at 50 C) which disappeared later as the droplets increased in size and became non-spherical (5000-6000 min at 50 C). The par-... 

Figure 3.9 The spherulites developed in (a) PEEK and (b) the typical polymers.

Figure 1.10 AFM phase images of spherulite development in PBA-C8. The temperature was 30 °C and the overall time was 167 min. Lei et al. [50], Reproduced with permission of Elsevier.

In addition to spherical entities, during an investigation of the growth of apatite in a glass-ceramic system sheaf-like objects were observed. Similar structures can be identified in polymeric systems, where they are believed to represent the precursors to full spherulitic development. Such entities have variously been described as axialites or hedrites, depending upon the crystallization conditions. 

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