Crystallization and orientation development in fiber and film processing of polypropylenes of varying stereoregular form and tacticity.: An article from: Polymer Engineering and Science
Book Details
Author(s)Dongman Choi, James L. White
PublisherSociety of Plastics Engineers, Inc.
ISBN / ASINB00082F9ME
ISBN-13978B00082F9M7
AvailabilityAvailable for download now
Sales Rank99,999,999
MarketplaceUnited States 🇺🇸
Description
This digital document is an article from Polymer Engineering and Science, published by Society of Plastics Engineers, Inc. on February 1, 2004. The length of the article is 5962 words. The page length shown above is based on a typical 300-word page. The article is delivered in HTML format and is available in your Amazon.com Digital Locker immediately after purchase. You can view it with any web browser.
From the author: We investigated the crystallization and orientation development in melt spinning and tubular blown film extrusion of several different types of polypropylenes, including conventional high tacticity isotactic polypropylenes (iPP) and metallocene catalyst low tacticity iPPs and syndiotactic polypropylenes (sPP). The fiber and film samples were characterized by wide-angle X-ray diffraction (WAXD), birefringence and differential scanning calorimetry (DSC). In melt spinning iPP, we found that the mesomorphic structure of iPP is more readily formed in lower tacticity fibers, and significant amounts of hexagonal [beta]-form crystals are found in low tacticity iPP fibers spun at high draw-down ratios. Low tacticity iPP fibers exhibited a significant decrease in the crystalline chain-axis orientation at high draw-down ratios, resulting from increased epitaxially branched lamellae. Melt-spun sPP fibers exhibit Form I helical structure at low spinning speeds and Form III zigzag all trans structure at high spinning speeds. We found that the level of spinline stress is the governing factor for this structural change. Melt-spun sPP fibers exhibit much higher chainaxis (c-axis) orientation factors ([f.sub.c]) and lower birefringence than iPP fibers spun at the same spinline stresses. In tubular blown sPP films, the a-axis of Form I unit cell tends to orient perpendicular to the film surface, while the b-axis of monoclinic [alpha] unit cell does so in iPP blown films.
Citation Details
Title: Crystallization and orientation development in fiber and film processing of polypropylenes of varying stereoregular form and tacticity.
Author: Dongman Choi
Publication:Polymer Engineering and Science (Refereed)
Date: February 1, 2004
Publisher: Society of Plastics Engineers, Inc.
Volume: 44 Issue: 2 Page: 210(13)
Distributed by Thomson Gale
From the author: We investigated the crystallization and orientation development in melt spinning and tubular blown film extrusion of several different types of polypropylenes, including conventional high tacticity isotactic polypropylenes (iPP) and metallocene catalyst low tacticity iPPs and syndiotactic polypropylenes (sPP). The fiber and film samples were characterized by wide-angle X-ray diffraction (WAXD), birefringence and differential scanning calorimetry (DSC). In melt spinning iPP, we found that the mesomorphic structure of iPP is more readily formed in lower tacticity fibers, and significant amounts of hexagonal [beta]-form crystals are found in low tacticity iPP fibers spun at high draw-down ratios. Low tacticity iPP fibers exhibited a significant decrease in the crystalline chain-axis orientation at high draw-down ratios, resulting from increased epitaxially branched lamellae. Melt-spun sPP fibers exhibit Form I helical structure at low spinning speeds and Form III zigzag all trans structure at high spinning speeds. We found that the level of spinline stress is the governing factor for this structural change. Melt-spun sPP fibers exhibit much higher chainaxis (c-axis) orientation factors ([f.sub.c]) and lower birefringence than iPP fibers spun at the same spinline stresses. In tubular blown sPP films, the a-axis of Form I unit cell tends to orient perpendicular to the film surface, while the b-axis of monoclinic [alpha] unit cell does so in iPP blown films.
Citation Details
Title: Crystallization and orientation development in fiber and film processing of polypropylenes of varying stereoregular form and tacticity.
Author: Dongman Choi
Publication:Polymer Engineering and Science (Refereed)
Date: February 1, 2004
Publisher: Society of Plastics Engineers, Inc.
Volume: 44 Issue: 2 Page: 210(13)
Distributed by Thomson Gale
