GROWTH OF POLYETHYLENE SINGLE-CRYSTALS FROM THE MELT - MORPHOLOGY

被引:91
|
作者
TODA, A [1 ]
KELLER, A [1 ]
机构
[1] UNIV BRISTOL, HH WILLS PHYS LAB, BRISTOL BS8 1TL, AVON, ENGLAND
关键词
POLYETHYLENE; CRYSTALLIZATION; MORPHOLOGY; SINGLE CRYSTAL; SPHERULITE; AXIALITE;
D O I
10.1007/BF00657415
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Three-dimensional shape of polyethylene single crystals grown from the melt has been studied. Two distinct types of lateral habit have been obtained: lenticular shape (type A) and truncated lozenge (type B) in the range of regime I and II. Electron microscopy has revealed chair-like shape of type B crystal and reconfirmed the planar shape of type A crystal. In the type B crystal, spiral growth has occurred frequently in the {110} sectors and the sense of the handedness of spiral terraces has been maintained. It has been suggested that the frequent occurrence of spiral growth is responsible for a morphological change (axialite-spherulite) accompanying the regime I-II transition. The origin of the chair-like crystals has been discussed and a possible mechanism has been suggested for the formation of spiral terraces; the mechanism is based on a distortion caused by the three-dimensional shape of chair-like crystals. It has been found that the chair-like crystals are curved in the opposite way to S-shaped lamellae observed by Bassett and Hodge in banded spherulites. In fact, the present work has led to the recognition of further classes of crystal with curving cross-sections and of distinctions between them. In final analysis, a unifying thread has been identified between lateral habits, growth kinetics and three-dimensional shape of lamellae, in turn, leading to some rationalization of multilayer developments including twisting in banded spherulites, the latter based on existing suggestions in the literature.
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页码:328 / 342
页数:15
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