Crystallization, polyethylene

The generation of an intermediate phase during melting under isometric conditions of orientationally crystallized polyethylene has also been observed56 at temperatures exceeding the melting temperature of ECC. The authors suppose that the mesophase... 

Fig. 5 Initial fold length L against undercooling AT = To - T for both melt- and solution-crystallized polyethylene, from different solvents [16]. Dashed line gives previous calculations (Model A [9], old model in Fig. 4), solid line shows the results from the new model in Fig. 4 after re-adjusting the energy of fusion per - CH2 - unit from E= 1.07 to E- 1.42 kcal/mol...

Fig. 10. Schematic structure models of the bulk-crystallized polyethylene samples. 1, II, and 111 indicate the crystalline, interfacial, and interzonal regions, respectively. Models A, B, C, D, and E express the molecular crystal, unpeeled crystal, disheveled unpeeled crystal, and lamellar crystals for medium and large molecular weight samples, respectively66), f and x designate the lamellar thickness and the extended molecular chain length, respectively...

In situ X-ray examination of crystallizing polyethylene, at high temperature and pressure, then confirmed this proposal in detail, showing that the wide-angle diffraction pattern changed abruptly with the optical texture [ 10]. That corresponding to the spherulitic texture was of the usual orthorhombic form while the new intermediate phase had two-dimensional hexagonal symmetry, with an increased cross-sectional area per chain, but without... 

Although a large number of substrates have been used to nucleate and crystallize polyethylene (14), only the wettabilities of polyethylenes... 

Hydrogen evolution from single crystals has been studied. Salovey et al. [271] found a G value of 4.6 for bulk Marlex-50 polyethylene and thin films obtained from solutions of crystallized polyethylene. Values of 2.48 and 2.17 were obtained by Kawai et al. [278] for, respectively, bulk Marlex-50 and single crystals (annealed or not). 

SAXS measurements of the lamellae thickness of solution crystallized polyethylene (PE) as a function of supercooling AT = Tm — Tc, where Tm and Tc are the melting and crystallization temperatures respectively, are in good agreement with the theory. It predicts, that the thickness of the lamellae, lc, is determined by the size of the critical nucleus, which is given by [30]... 

The effect of diluents on the melting behavior of polyethylenes has also been studied by Ke (168). A comparison between the melting transitions of solution and melt-crystallized polyethylene has been made. The measurement of the melting and second-order transitions of polyethylene tereph-thalate by DTA has been studied by Scott (169). Rudin et al. (170) measured the oxidation resistance of various polymers and rubbers by a DTA method. A comparison of the melting and freezing curves before and after oxidation provided the indication of the extent to which the polymer had been damaged or oxidized. 

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