Morphology

Abstract

Polymer morphology contains a uniquely detailed record of the history of a polymeric material, notably its crystallization and deformation and has been the key to understanding the fundamental aspects of such behavior. Early understanding gained from solution‐grown lamellae has been brought up to date for melt‐crystallized polymers. Spherulitic structure is now well characterized and is attributed to adjacent dominant lamellae repetitively branching and then diverging. The divergence is due to repulsion by cilia pressure and/or the nonparallel packing of initially rough surfaces. The differing environments and lamellar orientations within spherulites lead to an inherent, spatially varying, spread of properties characteristic of semicrystalline polymers. The latest findings, that fold surfaces generally transform behind the growth front and that a memory of the initial transverse morphology is retained on drawing to very high extensions, give key insights, respectively, into banded growth as a means of relieving surface stress and into the details of deformation.

3D Morphology of Different Crystal Forms in β-Nucleated and Fiber-Sheared Polypropylene: α-Teardrops, α-Teeth, and β-Fans

“…Combining these facts and the relevant literature, , the highly birefringent spherulites can be assigned to the β-spherulites induced by β-nucleating agent, and those with weak birefringence are attributed to α-spherulites. Their low birefringence is due to partial cancellation of path difference coming from radial (dominant) and tangential (subsidiary, or “daughter”) lamellae, characteristic of α-spherulites . Optical retardation can be estimated from the colors in Figure d using the Michel–Levy chart (see inset).…”

“…Their low birefringence is due to partial cancellation of path difference coming from radial (dominant) and tangential (subsidiary, or “daughter”) lamellae, characteristic of α-spherulites. 41 Optical retardation can be estimated from the colors in Figure 1 d using the Michel–Levy chart (see inset).…”

High-Frequency Ultrasonic Spectroscopy of Structure Gradients in Injection-Molded PEEK Using a Focusing Transducer

“…Shear-induced and thermally induced crystallization take place competitively and form geometrically different structures. In contrast to thermally induced spherulites [21], shear-induced crystals exhibit anisotropic mechanical properties [22]. Due to the stiff polymer chains of PEEK, this shear-induced anisotropy is particularly pronounced due to the stiffer and more elastic behavior in the chain direction.…”