Effects of molecular weight on the perforation impact behavior of injection-molded plaques of α-and β-phase isotactic polypropylenes
作者:
J. Karger-kocsis,
E. Moos,
I. Mudra,
J. Varga,
期刊:
Journal of Macromolecular Science, Part B
(Taylor Available online 1999)
卷期:
Volume 38,
issue 5-6
页码: 647-662
ISSN:0022-2348
年代: 1999
DOI:10.1080/00222349908248128
出版商: Taylor & Francis Group
关键词: α-phase;β-phase;Injection molding;Instrumented falling weight impact;Isotactic polypropylene;Molecular weight;Skin-core morphology.
数据来源: Taylor
摘要:
This study was devoted to the instrumented falling weight impact (IFWI) behavior of injection-molded a-and β-phase isotactic polypropylene (iPP) homopolymers. The perforation impact response of iPP with various melt flow indices (MFIs), and thus molecular weight (MW) characteristics, was studied at two different temperatures (T= 23°C andT=−40°C) and incident impact speeds (vinc= 5 and 10 m/s). The impact resistance of β-iPP was superior to the α-modification. The absolute resistance to perforation increased with increasing MW or decreasing MFI, whereas the relative toughness improvement between the β-and α-iPPs followed an opposite tendency. The molding-induced skin-core morphology did not affect practically the out-of-plane response of the impacted plaques. Changes in the fractograms (viz. force-time curves) under various experimental conditions were traced to variations in the failure mode, showing a competition between radial and circumferential cracking with respect to the clamping ring. In the case of the more ductile β-iPP. circumferential cracking was favored.
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