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Title: The Role of High Molecular Weight Chains in Flow-Induced Crystallization Precursor Structures

Abstract

Flow-induced crystallization in a bimodal polyethylene blend was investigated by means of in situ shear-WAXD (wide-angle x-ray diffraction) and shear-SAXS (small-angle x-ray scattering) techniques. The blend contained a low molecular weight (M{sub w} = 50 000 g mol{sup -1} and polydispersity = 2) polyethylene copolymer matrix (MB-50k) with 2 mol% of hexene, and a nearly monodisperse high molecular weight (M{sub w} = 161 000 g mol{sup -1} and polydispersity = 1.1) hydrogenated polybutadiene component (MD-161k), which has the microstructure of an ethylene-butene copolymer with 4 mol% butene. At the experimental temperatures of 112 and 115 C, MB-50k exhibited faster crystallization kinetics and higher crystallinity due to higher chain mobility and higher ethylene content than those of the MB-50k/MD-161k blend. However, both WAXD and SAXS results indicated that the high molecular weight component (MD-161k) is responsible for the formation of more highly oriented crystals, which we relate to a shear-induced precursor scaffold. Values of the lamellar long period in all experimental runs were found to slightly decrease in the beginning of crystallization and then reached a plateau value. Vonk's method for single lamella scattering was employed to estimate the lamellar thickness in the MB-50k/MD-161k blend at high temperature (115 C), wheremore » the lamellar thickness was also found to decrease in the beginning and remained about constant afterward. Twisted lamellar structures were observed in all formed kebabs.« less

Authors:
; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
930132
Report Number(s):
BNL-80778-2008-JA
TRN: US200822%%1196
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physics: Condensed Matter; Journal Volume: 18
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; COPOLYMERS; CRYSTALLIZATION; MICROSTRUCTURE; MOLECULAR WEIGHT; POLYETHYLENES; PRECURSOR; X-RAY DIFFRACTION; SMALL ANGLE SCATTERING; BUTADIENE; national synchrotron light source

Citation Formats

Yang,L., Somani, R., Scis, I., Hsiao, B., Kolb, R., and Lohse, D. The Role of High Molecular Weight Chains in Flow-Induced Crystallization Precursor Structures. United States: N. p., 2006. Web. doi:10.1088/0953-8984/18/36/S15.
Yang,L., Somani, R., Scis, I., Hsiao, B., Kolb, R., & Lohse, D. The Role of High Molecular Weight Chains in Flow-Induced Crystallization Precursor Structures. United States. doi:10.1088/0953-8984/18/36/S15.
Yang,L., Somani, R., Scis, I., Hsiao, B., Kolb, R., and Lohse, D. Sun . "The Role of High Molecular Weight Chains in Flow-Induced Crystallization Precursor Structures". United States. doi:10.1088/0953-8984/18/36/S15.
@article{osti_930132,
title = {The Role of High Molecular Weight Chains in Flow-Induced Crystallization Precursor Structures},
author = {Yang,L. and Somani, R. and Scis, I. and Hsiao, B. and Kolb, R. and Lohse, D.},
abstractNote = {Flow-induced crystallization in a bimodal polyethylene blend was investigated by means of in situ shear-WAXD (wide-angle x-ray diffraction) and shear-SAXS (small-angle x-ray scattering) techniques. The blend contained a low molecular weight (M{sub w} = 50 000 g mol{sup -1} and polydispersity = 2) polyethylene copolymer matrix (MB-50k) with 2 mol% of hexene, and a nearly monodisperse high molecular weight (M{sub w} = 161 000 g mol{sup -1} and polydispersity = 1.1) hydrogenated polybutadiene component (MD-161k), which has the microstructure of an ethylene-butene copolymer with 4 mol% butene. At the experimental temperatures of 112 and 115 C, MB-50k exhibited faster crystallization kinetics and higher crystallinity due to higher chain mobility and higher ethylene content than those of the MB-50k/MD-161k blend. However, both WAXD and SAXS results indicated that the high molecular weight component (MD-161k) is responsible for the formation of more highly oriented crystals, which we relate to a shear-induced precursor scaffold. Values of the lamellar long period in all experimental runs were found to slightly decrease in the beginning of crystallization and then reached a plateau value. Vonk's method for single lamella scattering was employed to estimate the lamellar thickness in the MB-50k/MD-161k blend at high temperature (115 C), where the lamellar thickness was also found to decrease in the beginning and remained about constant afterward. Twisted lamellar structures were observed in all formed kebabs.},
doi = {10.1088/0953-8984/18/36/S15},
journal = {Journal of Physics: Condensed Matter},
number = ,
volume = 18,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}