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Effect of the Distribution of Short-Chain Branches on Crystallization Kinetics and Mechanical Properties of High-Density Polyethylene

Krishnaswamy, Rajendra K. and Yang, Qing and Fernandez-Ballester, Lucia and Kornfield, Julia A. (2008) Effect of the Distribution of Short-Chain Branches on Crystallization Kinetics and Mechanical Properties of High-Density Polyethylene. Macromolecules, 41 (5). pp. 1693-1704. ISSN 0024-9297. https://resolver.caltech.edu/CaltechAUTHORS:20170724-102215381

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Abstract

The effects of the placement of short-chain branches (SCB) on crystallization kinetics, morphology and mechanical properties of high-density polyethylene (HDPE) are examined using bimodal blends of short (S ∼40 kg/mol) and long (L ∼400 kg/mol and 550 kg/mol) polyethylenes with SCB (1-hexene comonomer) incorporated in either the high or the low molecular weight component. A pair of blends that has nearly matched molecular weight distribution and average SCB content shows that placement of branches preferentially on the longer molecules results in slower crystallization kinetics at high crystallization temperatures relative to the material with branches on the short chains. Blends with SCB on the high molecular weight components have superior ultimate mechanical properties, and their resistance to slow crack growth is tremendously enhanced. These improved mechanical properties are attributed to an increase in the amount of tie chains that form when branches are placed on the long chains. A conceptual model based on the interplay of inherent crystallization kinetics of each species and their competition at the growth front in binary blends qualitatively explains the effects of SCB distribution on crystallization kinetics, lamellar thickness and inferred formation of tie chains.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/ma070454hDOIArticle
http://pubs.acs.org/doi/abs/10.1021/ma070454hPublisherArticle
ORCID:
AuthorORCID
Kornfield, Julia A.0000-0001-6746-8634
Additional Information:© 2008 American Chemical Society. Received 21 February 2007. Published online 8 February 2008. Published in print 1 March 2008. The authors would like to acknowledge useful discussions with Prof. Stephen Cheng (University of Akron) and Prof. Garth Wilkes (Virginia Tech). Dr. Paul DesLauriers and Dr. David Rohlfing are acknowledged for molecular weight and rheological characterization of the polymers and blends. The authors are also grateful to Barbara Lewis, Jim French, Jerry Stark, David Higbee, Tim Harper, and Delores Henson for performing most of the experiments. Financial support by the National Science Foundation (Grants DMI-0218112 and DMI-0523083) is acknowledged.
Funders:
Funding AgencyGrant Number
NSFDMI-0218112
NSFDMI-0523083
Issue or Number:5
Record Number:CaltechAUTHORS:20170724-102215381
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20170724-102215381
Official Citation:Effect of the Distribution of Short-Chain Branches on Crystallization Kinetics and Mechanical Properties of High-Density Polyethylene Rajendra K. Krishnaswamy, Qing Yang, Lucia Fernandez-Ballester, and Julia A. Kornfield Macromolecules 2008 41 (5), 1693-1704 DOI: 10.1021/ma070454h
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:79296
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:24 Jul 2017 18:12
Last Modified:03 Oct 2019 18:18

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