ISSN:
0032-3888
Keywords:
Chemistry
;
Chemical Engineering
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
,
Physics
Notes:
The dynamic tensile deformation mechanism of spherulitic poly-alpha-olefins, high-density polyethylene, isotactic polypropylene, and isotactic polybutene-1, was investigated by dynamic X-ray diffraction at various temperatures and frequencies in order to assign the α and β mechanical dispersions explicitly. The uniaxial orientation distribution function qj(ζj, 0) of the j-th crystal plane and its dynamic response Δqj′(ζj, 0) in-phase with dynamic strain were observed for several crystal planes, and then the orientation distribution function ω(§, 0, η) of crystallites (crystal grains) and its dynamic response Δω′(§, 0, η), also in-phase with the dynamic strain, were determined by a mathematical transformation procedure proposed by Roe and Krigbaum on the basis of the Legendre addition theorem. The temperature and frequency dependences of Δω′(§, 0, η) were analyzed in terms of a spherulite deformation model combining affine orientation of crystal lamellae with several types of preferential reorientation of the crystal grains within the orienting lamellae. The following assignments are made: (1) the a mechanical dispersion must be assigned to the dynamic orientation dispersions of crystal grains within lamellae involving two types of preferential rotations of the grains associated with lamellar detwisting mostly in the equatorial zone of uniaxially deformed spherulites and with lamellar tilting mostly in the polar zone of the spherulites. Both processes are intralamellar grain-boundary phenomena, and the former process of lamellar detwisting is hardly activated for polypropylene and polybutene-1 spherulites in contrast to polyethylene spherulites. (2) The β mechanical dispersion must be assigned to the dynamic orientation dispersion of the crystal lamellae behaving as rigid bodies unaccompanied by reorientation of crystal grains within the orienting lamellae. This process is an interlamellar grain-boundary phenomenon.
Additional Material:
15 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pen.760240511
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