On shish-kebab morphologies in crystalline polymers

Shish-kebabs or row structures consist of transverse lamellae growing from a central linear thread all with a common chain axis direction parallel to the central nucleus. Attention is drawn to the fact that adjacent lamellae are not in contact; in melt-crystallized alpha-polypropylene the separation is generally 3-4 nm. Moreover, lamellae in asymmetric environments, such as the ends of rows, are often elastically curved outwards. Both observations support proposals concerning the importance of cilia for melt-crystallized growth and the development of spherulites but would have been difficult to establish without the advantage of oriented nucleation. The former leads to values for the effective dimensions of cilia, the latter to values of the pressure they exert on an adjacent lamella. The advantages of using linear rather than point nuclei in evaluating melt-crystallized morphologies are emphasized. Copyright (C) 1996 Elsevier Science Ltd.