Elsevier

Polymer

Volume 9, 1968, Pages 23-40
Polymer

Morphology of polypropylene crystallized from the melt

https://doi.org/10.1016/0032-3861(68)90006-2 Get rights and content

Abstract

The lamellar build-up of polypropylene α-spherulites is different from the radiating lamellar structure of polyethylene and several other polymers. In the initial stage of crystallization quadrites are found, parallelogram-shaped aggregates of two sets of lamellae crossing at an angle of about 80°. The cross-hatched pattern persists during the growth of the spherulites, and explains their low birefringence. Crystallographically the cross-hatching is accounted for by an epitaxial fit of lamellae contacting along (010) faces. The dependence of birefringence on temperature of crystallization finds a qualitative explanation in the temperature dependence of epitaxial nucleation. The cross-hatched pattern suggests for polypropylene a deformation mechanism different from that of polyethylene and may account for the lower tendency to warpage of polypropylene.

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