Problems relating to long period determination in polyethylene shish‐kebab structures

Abstract

The X-ray long periods from high molecular weight injection molded polyethylene (PE) with a shish-kebab structure have been compared with values derived f'rom electron micrographs. It is shown that while small angle X-ray scattering (SAXS) presents two long periods, the direct measurements from transmission electron microscopy (TEM) furnish only the lower SAXS periodicity. In an attempt to clarify this discrepancy of results, laser light diffraction and Fourier transformation of electron micrographs have been undertaken. Using this method two long periods are found in all regions investigated. Results are discussed in terms of the role played by the structured or "weakly crystalline" interlamellar parts, containing a lower electron density, which are neglected by the small angle scattering of X-rays and which give rise in particular regions to larger scattering periodicities.

Deformation Mechanisms of Semi-Crystalline Polymers on the Submicron Scale

“…This indicates that the used tapping mode reacts very sensitive to also very small variations in the local degree of crystallinity (or density). These results confirm that crystallisation of PE from the melt appears in smaller crystals, which are interrupted by defect layers and arranged like strings of beads (MICHLER et al 1986;HISS et al;HECK et al). The deformation mechanisms of lamellae in the local deformation zones of crazes are comparable with that in the matrix strands at and between the soft modifier particles in the PE blends.…”

Investigation of Micromechanical Behavior and Voiding of Polyethylene Terephthalate/Polyethylene-stat-methyl Acrylate Blends during Tensile Deformation

“…Therefore, the electron density difference between these thin defective lamellae and the amorphous material is strongly reduced and may not contribute to the scattering in some regions. As a result, larger long periods are detected by SAXS if one neglects these structures that are contained between well-defined thick lamellae. , Only one maximum was observed for the F MA = 10 and 20 wt % copolymers. The long spacing of the p­(E- s -MA) copolymers, plotted in Figure S4, decreases with an increase in F MA from 0 to 20 wt %, suggesting smaller lamellae are formed.…”

Problems relating to long period determination in polyethylene shish‐kebab structures

“…2). Thin lamellae contain the highest amount of crystalline defects in the form of chain ends or branchings [8,9]. During cooling from the melt, these thinnest lamellae are produced at a late stage between the earlier crystallized thick lamellae, i. e., they are produced in a melt with a higher content of defects and a greater hindrance of molecular mobility [ 10, 1 11.…”

“…Quantitative determination of the thickness, the thickness distribution and the long period of the lamellae stacking were determined by direct measurement on the electron micrographs and by using the contrast distribution between lamellae and interlamellar amorphous regions measured in a micro-densitometer [7]. To determine the long period, laser light diffraction on the negatives of electron micrographs has been used as a third method.…”