A regularizationfree method for the calculation of molecular weight distributions from dynamic moduli data
 Job D. Guzmán,
 Jay D. Schieber,
 Richard Pollard
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There are several models for the determination of molecular weight distributions (MWDs) of linear, entangled, polymer melts via rheometry. Typically, however, models require a priori knowledge of the critical molecular weight, the plateau modulus, and parameters relating relaxation time and molecular weight (e.g., k and α in τ=kM ^{α}). Also, in an effort to obtain the most general MWD or to describe certain polymer relaxation mechanisms, models often rely on the inversion of integral equations via regularization. Here, the inversion of integral equations is avoided by using a simple doublereptation model and assuming that the MWD can be described by an analytic function. Moreover, by taking advantage of dimensionless variables and explicit analytic relations, we have developed an unambiguous and virtually parameterfree methodology for the determination of MWDs via rheometry. Unimodal MWDs have been determined using only a priori knowledge of the exponent α and dynamic moduli data. In addition, the uncertainty in rheological MWD determinations has been quantified, and it is shown that the reliability of the predictions is greater for the highmolecularweight portion of the distribution.
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 Title
 A regularizationfree method for the calculation of molecular weight distributions from dynamic moduli data
 Journal

Rheologica Acta
Volume 44, Issue 4 , pp 342351
 Cover Date
 20050401
 DOI
 10.1007/s0039700404143
 Print ISSN
 00354511
 Online ISSN
 14351528
 Publisher
 SpringerVerlag
 Additional Links
 Keywords

 Molecular weight distribution
 Uncertainty
 Dynamic moduli
 Industry Sectors
 Authors

 Job D. Guzmán ^{(1)} ^{(2)}
 Jay D. Schieber ^{(1)}
 Richard Pollard ^{(2)}
 Author Affiliations

 1. Department of Chemical Engineering, Illinois Institute of Technology, Chicago, IL, 60616, USA
 2. The Dow Chemical Company, Freeport, TX, 77541, USA