Nature of Crystallization Precursors

Mitsuhashi [84] reported for the first time the formation of string-like polyethylene (PE) structures during stirring 

Model PE blends consisting of a low molecular weight (LMW) matrix that was kept amorphous by choosing the experimental temperature higher than its melting temperature, that is, acting as a solvent, and a crystallizable HMW minor component were studied by Hsiao and coworkers [85]. Such special blends allow for the examination of the crystallization behavior under fiow of the HMW component only. Shish formation was directly observable from SAXS measurements for sufficiently high HMW concentration and indirectly from WAXD (oriented kebab). 

Electron micrographs, made after dissolving the LMW component, showed an unexpected shish-kebab structure for these special blends adjacent kebabs are interconnected by multiple short shish, quite different from the conventional results/view of one shish connecting multiple kebabs (see Fig. 14.7). It is not clear whether this is a result of the special blend or also applies to normal entangled blends. Nevertheless, based on these results Hsiao et al. [85] proposed a model for the shish-kebab formation not discussed in detail here. 

A bimodal system with the opposite behavior, namely an HMW atactic polypropylene as the precursor com- 

All structures can also be found over the thickness of a sample from a slit flow (see for example Cust6dio et al. [74]). 

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