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Investigation of the molecular weight of polyethylene using rheological techniques
Author(s) -
Li Pengpeng,
Yang Shiyuan,
Wang Meiling
Publication year - 2012
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.36862
Subject(s) - rheology , branching (polymer chemistry) , polyethylene , gel permeation chromatography , polymer , materials science , polymer chemistry , viscosity , molar mass distribution , relaxation (psychology) , intrinsic viscosity , thermodynamics , analytical chemistry (journal) , chemistry , composite material , chromatography , physics , psychology , social psychology
Abstract The zero shear viscosity (η 0 ), relaxation time, relaxation spectrum index (RSI) of 20 metallocene‐catalyzed, and conventional polyethylenes are presented. The effect of molecular weight ( M w ) determined by gel‐permeation chromatography on rheology parameters was analyzed. The dependence of zero shear viscosity or relaxation time on molecular weight allowed the polyethylene samples to be separated into three different groups and different values of parameter in ${\eta _{\rm{0}}} = K{{\rm{(}}{M_w})^\alpha }$ were obtained, respectively. Two groups of polymers display viscosity deviation from linear relationship and the reason was attributed to different level of long‐chain branching and high‐molecular weight tails. The intrinsic reason was disclosed when relaxation spectra at frequencies between 1 s and 10 s were involved and RSI was used for quantitative analysis. Thus, an alternative single rheological method, based on the effect of molecular structure on dynamic rheological behaviors, was proposed to evaluate the molecular weight of polyethylene. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012