Comparative study of structure and tensile properties of melt-pressed and extruded-blown films of high-density polyethylene

Citation
S. Murakami et al., Comparative study of structure and tensile properties of melt-pressed and extruded-blown films of high-density polyethylene, J MACR S PH, B39(5-6), 2000, pp. 645-655
Citations number
19
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
JOURNAL OF MACROMOLECULAR SCIENCE-PHYSICS
ISSN journal
0022-2348 → ACNP
Volume
B39
Issue
5-6
Year of publication
2000
Pages
645 - 655
Database
ISI
SICI code
0022-2348(2000)B39:5-6<645:CSOSAT>2.0.ZU;2-N
Abstract
Bulk high-density polyethylene (HDPE) films crystallized from isotropic mel ts show a spherulite structure; the tensile stress-strain (S-S) curves of s uch melt-pressed (M-P) films show a characteristic shape caused by necking. On the other hand, extruded-blown (E-B) HDPE films show an anisotropic str ucture in which lamellae are stacked normal to the extrusion direction. The S-S curves of E-B films showed various shapes for various elongation direc tions relative to the lamellar orientation direction. When drawn perpendicu lar to the extrusion direction (parallel to the lamellar orientation direct ion), the S-S curve showed typical necking behavior resulting from unfoldin g from one part of the lamellae. When drawn diagonal to the extrusion direc tion (diagonal to the lamellar orientation direction), the yield stress was smaller due to slippage between the lamellae. When drawn parallel to the e xtrusion direction (perpendicular to the lamellar orientation direction), t he S-S curve was smooth, but it was shown that micronecking occurred repeat edly in various parts of the specimen. The characteristic shape of the S-S curve of the M-P films was reconstructed as the sum of all S-S curves of th e E-B films in various directions. From a structural viewpoint, the deforma tion behavior of the bulk film, which has a spherulite structure, can be si mulated at least qualitatively by the deformation behavior of anisotropic E -B films in various directions.