Polyethylene crystallization from

Wunderlich, B. and Arakawa, T. Polyethylene crystallized from the melt under elevated pressure, J. Polymer Sci., Part A, 2, 3697 (1964)... 

Linear Polyethylene Crystallized from Dilute Solution. 61... 

To elucidate the phase structure in detail it is necessary to characterize the molecular chain conformation and dynamics in each phase. However, it is rather difficult to obtain such molecular information, particularly of the noncrystalline component, because it is substantially amorphous. In early research in this field, broad-line H NMR analysis showed that linear polyethylene crystallized from the melt comprises three components with different molecular mobilities solid, liquid-like and intermediate molecular mobility [13-16]. The solid component was attributed to molecules in the crystalline region, the liquid component to... 

Geil PH, Anderson F, Wunderlich B, Arakawa T (1964) Morphology of polyethylene crystallized from the melt under pressure. Polym Sci A 2 3707... 

Marlex 5003 polyethylene crystallized from 0.04% solution in xylene at 85°C. then molded into 10 mil. sheets at 160°C. No surface treatment A—Polyethylene film (untreated) exposed to vapors of a boiling 1.1 hexane, heptane mixture for 5 minutes A—Polyethylene film (untreated) irradiated with a Van de Graaff generator to a dose of 10 Mrads O—Polyethylene film exposed to glass cleaning solution at 80°C. for 4 minutes... 

The y relaxation of polyethylene, expressed in terms of tan 5, is centered in the vicinity of — 120°C at 1 Hz. This relaxation is believed to be caused by molecular motions occurring in the amorphous phase as indicated by the fact that the relaxation is very weak in highly crystalline polyethylene crystallized from dilute solutions (39,40). The relatively high intensity and universality of the y relaxation in polyethylenes, independent of whether they do or do not have branches in their structure, seems to suggest that the y relaxation may be associated with the glass transition. According to this interpretation, the glass transition temperature of polyethylene would be located in the vicinity of — 120°C. 

Figure 12.34 Loss compliance isotherms in the frequency domain of linear polyethylene crystallized from the melt. (From Ref. 44.)...

Significantly different seemed intiaUy the crystal morphology of polyethylene, polybutene-1, polypropylene, polystyrene, poly(4-methyl pen-tene-1), and polyisoprene polymerized with varying solvents and at varying temperatures (114, 123). Discrete hollow particles with a fibrous texture could be observed. The fibrils had an appearance similar to polyethylene crystallized from solution sheared by rapid stirring (118). A closer analysis of this similarity was carried out by Wikjord and Manley (124), Keller and Willmouth (117), and Ingram and Schindler (125) for polyethylene. 

A preferentially and a sheaf-like aggregation with random in-plane orientation are observed for the thinner films (thicknesses of 0.1, 0.2 and 0.4 pm in panels a-c). By contrast thick films (0.6 pm and thicker, panel d) show a morphology that resembles the well known (bulk) spherulitic form with a banded structure, characteristic of linear polyethylene crystallized from the melt at moderately high undercooling. 

Y.M. Boiko, W. Brostow, A.Y. Goldman, A.C. Ramamurthy, Tensile, stress relaxation and dynamic mechanical behaviour of polyethylene crystallized from highly deformed melts. Polymer, 36 (7), 1383-1392,1995. 

Small Angle Scattering Study of Polyethylene Crystallization from Solutions... 

We have learned several things from the current SANS study of polyethylene crystallization from concentrated solutions. (1) The detection sensitivity of the volume fraction degree of crystallinity is estimated to be 10 . That allows for measuring the kinetics during the induction stage of polymer crystallization. 

Fig. 5. A graph showing the variation of the fold length (1) with supercooling (AT) for polyethylene crystallized from a variety of solvents and from the melt. In the case of solvent crystallization, supercooling is taken with respect to the so-called equilibrium dissolution temperature. For the melt-crystallized data set the equilibrium melting temperature is used. The remarkable coincidence between the curves, despite the wide range of absolute temperatures to which each supercooling corresponds, is strong evidence in favor of the kinetic origin of crystal thickness selection. Solvents xylene, hexyl acetate, 0 ethyl esters, O dodecanol, V dodecane, A octane, x tetradecanol, + hexadecane, melt crystallized. Reprinted from Ref. 44. Copsright (1985), with permission from Kluwer Academic Publishers.

Fig. 8. An AFM topographic image showing a group of single crystals of polyethylene crystallized from xylene at 70°C. The grey scale shows the variation in height, from which the very uniform thickness of the crystal can be clearly seen. (Unpublished data image courtesy of Dr. A. K. Winkel).

Fig. 1. A truncated lozenge of linear polyethylene, crystallized from 0.01% solution in xylene, with boundaries delineating its six sectors and a step at the outer edge where the crystallization temperature was reduced from 90 to 76 = C. From Ref. 18.

Wignall et looked for the existence of (100) and (010) powder diffraction peaks in the scattering pattern of a mixture of deuteriated and protonated polyethylene, crystallized from both the melt and solution. In an untagged polymer these two reflections should have zero intensity because the structure factors contain two identical components, out of phase by 180°, which cancel exactly. 

Abo el Maaty MI, Bassett DC (2005) Evidence for isothermal lamellar thickening at and behind the growth front as polyethylene crystallizes from the melt. Polymer 46 8682-8688 Abo el Maaty MI, Bassett DC (2006) On the time for fold surfaces to order during the crystallization of polyethylene from the melt and its dependence on molecular parameters. Polymer 47 7469-7476... 

Abo El Maaty MI, Bassett MD (2005) Evidence for isothermal lamellar thickening at and behind the growth front as polyethylene crystallizes from the melt. Polymer 46(20) 8682-8688... 

Finally, the one-dimensional geometry of nanotubes provides exciting opportunities for controlled nucleation and growth of single crystals along individual fibers, as for example with polyamide-6,6 and polyethylene crystallized from solution, allowing for control of crystallite periodicity and molecular-level architecture. This unique capability of nanotubes can conceivably lead to special types of functionalization of individual nanotubes, which can be exploited to improve interactions (see our discussion of better interfacial coupling) and control dispersion in selected polymer matrices. 

J The bond polarizabilities determined for alkanes (Table 19) are used to calculate polarizabilities (per CH2) for the polyethylene crystal. From Ref. 127. 

Fig. V.I. Inter-hydrogm contacts (Pi P4) of the orthorhombic polyethylene crystaL From Tasumi and Shimanouchi (1%5)...

Fig. V.4(a) 4(h). Frequency-dispersion curves of the orthorhombic polyethylene crystal. From Kitagawa (1969), Kitagawa and Miyazawa (1968 a)...

---