The dependence of IR absorption spectrum on the type of symmetry of crystallographic cells allows us to investigate the kinetics of the development of phase transitions. Using the proposed technique, confirmations of the structural first order phase transition are obtained and the existence of conformational defects is proved.
The dependence of the IR absorption spectrum on the type of symmetry of crystallographic cells allowed us to investigate the kinetics of phase transitions. It is confirmed that the first order solid-phase transition develops by a heterogeneous mechanism in a narrow temperature range ΔT ⩾ 1 K.
The morphology of virgin reactor powder (RP) of high-density polyethylene HDPE with MW = 160,000 g/mol was investigated with the help of DSC, SEM, SAXS and WAXS methods. The morphological SEM analysis showed, that the main morphological units of RP are macro- and micro-shish kebab structures with significantly different geometric dimensions, as well as individual lamellae of folded chain crystals. Quantitative analysis of an asymmetric SAXS reflection made it possible to reveal the presence of several periodic morphoses in the RP with long periods from 20 nm to 60 nm and to correlate them with the observed powder morphology. According to the DSC crystallinity data, the thickness of the lamellae in each long period was estimated. Their surface energy was calculated in the framework of the Gibbs-Thompson theory. The presence of regular and irregular folds on the surface of the different shish-kebab lamellae is discussed. The percentage of identified morphoses in the RP was calculated. It has been suggested that the specific structure of HDPE RP is due to the peculiarity of polymer crystallization during suspension synthesis in a quasi-stationary regime, in which local overheating and inhomogeneous distribution of shear stresses in a chemical reactor are possible.
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