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Triple-Detector GPC Characterization and Processing Behavior of Long-Chain-Branched Polyethylene Prepared by Solution Polymerization With Constrained Geometry Catalyst

Published

Author(s)

W Wang, S B. Kharchenko, Kalman D. Migler, S Zhu

Abstract

Fourteen long-chain branched (LCB) polyethylene (PE) samples were prepared by a constrained geometry catalyst. The PE samples had average branching frequencies of 0.06 to 0.98 branches per polymer chain, determined by 13C NMR. These samples as well as five linear PEs were characterized using a gel permeation chromatography (GPC) coupled with on-line three-angle laser light scattering (LS), differential refractive index (DRI), and viscosity (CV) detectors. The root mean-square radius of gyration (), intrinsic viscosity ([h]), and molecular mass (M) of the PEs were measured for each elusion fraction. Based on the comparison of the LCB PEs with their linear counterparts and the Zimm-Stockmayer equation, the distributions of long-chain branch frequency (LCBF) and density (LCBD) as function of molecular mass were estimated. It was found that although the LCBF increased with the increase of molecular mass, the LCBD showed a maximum value in the medium molecular mass range for most of the PE samples.The average LCBD data from the GPC analysis were in good agreement with the 13C NMR measurements. The rheological properties and processing behavior of these samples were also assessed. While the long chain branching showed significant effects on the modulus and viscosity, it did not improve the processing. Compared to linear PE, polymer melt flow instabilities such as sharkskin, stick-slip and gross melt fracture developed in extrusion of LCB PEs occurred at lower wall shear stresses and apparent shear rates.
Citation
Plasma Processes and Polymers
Volume
45
Issue
No. 19

Keywords

extrusion, long-chain branching, metallocene, molecular architecture, polyethylene, sharkskin

Citation

Wang, W. , Kharchenko, S. , Migler, K. and Zhu, S. (2004), Triple-Detector GPC Characterization and Processing Behavior of Long-Chain-Branched Polyethylene Prepared by Solution Polymerization With Constrained Geometry Catalyst, Plasma Processes and Polymers, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=852341 (Accessed April 13, 2024)
Created August 31, 2004, Updated October 12, 2021