Shish-kebab precursors

Somani R H, Yang L, Zhu L and Hsiao B S (2005) Flow-induced shish kebabs precursor structures in entangled polymer melts. Polymer 46 8587-8623. 

Somani RH, Yang L, Zhu L, Hsiao BS (2005) Flow-induced shish-kebab precursor structures in entangled polymer melts. Polymer 46 8587-8623 Sorrentino A, De Santis F, Titomanlio G (2007) Polymer crystallization under high cooling rate and pressure a step towards polymer processing conditions. Lect Notes Phys 714 329-344 Stocker W, Magonov SN, Cantow HI, Wittmann JC, Lotz B (1993) Contact faces of epitaxially crystallized a- and y-phase isotactic polypropylene observed by atomic force microscopy. Macromolecules 26 5915-5923... 

The epitaxial growth and the formation of a shish-kebab stmcture were also investigated in high molecular weight iPP (HMW-iPP)/low-molecular-weight LLDPE (LMW-LLDPE) blends [21]. The formation of the initial crystallization precursor structure was investigated by using synchrotron WAXS/SAXS techniques at 130 and 140 °C. Shear was applied at temperatures above the cloud points of these blends, and therefore, the HMW-iPP chains could form a flow-induced crystalline stmcture in the blends only at 6 and 9 wt% of HMW-iPP LMW-LLDPE merely served as the amorphous matrix (Fig. 5.3). When the HMW-iPP... 

Fig. 8.1. Schematic representation of flow-induced precursor structures at different stages (A) before shear, (B) formation of precursor structures containing linear nuclei (shish), (C) formation of shish-kebab morphology. (Reprinted with permission from [21])...

Hayashi Y, Matsuba G, Zhao Y, Nishida K and Kanaya T (2009) Precursor of shish kebab in isotactic polystjuene under shear flow. Polymer 50 2095-2103. 

There are a number of other possible interpretations of the data. The Si S peak could be due to the formation of oriented nuclei, foe precursor to the shish in shish-kebab crystals and row nucleation [28], but this should also lead to orientation in the WAXS which is not observed. Furthermore, foe elongation is less than a foctor of 2 which is very low for formation of such structures [7,2]. 

Fig. 8.10. Schematic representation of the entanglement network of HMVIT E chains (A) under uniaxial deformation (LMVIT E chains are not shown here). E pon shearing, some chain segments between entanglements (shown as round dots) are stretched along the flow direction, but most segments remained in the coiled state (B). The stretched segments form the precursors for the shish formation, and the coiled segments can grow into kebabs (reprinted with permission from [27])...

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