Rheological measurement of molecular weight distribution of polymers

e-Polymers ◽  
2013 ◽  
Vol 13 (1) ◽  
Author(s):  
Maryam Khak ◽  
Ahmad S. A. Ramazani
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Loss Modulus ◽  
Method Comparison ◽  
Polymeric Materials ◽  
Linear Polymers ◽  
Rheological Data ◽  
Log Normal ◽  
The Relationship

Abstract This paper has described a method to obtain the molecular weight distribution (MWD) of polymeric materials from their rheological data. The method has been developed for linear polymers with log normal molecular weight distribution. The rheological data required to obtain the molecular weight distribution are the shear storage modulus,G' (ω) , and shear loss modulus,G" (ω) , extending from the terminal zone to the plateau region. For determining the molecular weight average, the method uses the relationship between stress moduli and relaxation spectrums, with the equation that connects dynamic rheological data with molecular weight distribution, and so it is not necessary to achieve the relaxation spectrums and the molecular weight distribution is obtained directly from dynamic shear experiments and it is one of the main advantageous of the proposed method. Comparison of calculated and experimental data obtained by GPC for five polypropylene samples produced in different conditions show that model can correctly predict molecular weight distribution for these types of polymers.

Tuning dispersity of linear polymers and polymeric brushes grown from nanoparticles by atom transfer radical polymerization

2021 ◽  
Author(s):  
Rongguan Yin ◽  
Zongyu Wang ◽  
Michael R. Bockstaller ◽  
Krzysztof Matyjaszewski
Keyword(s):  
Molecular Weight ◽  
Atom Transfer Radical Polymerization ◽  
Radical Polymerization ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Polymeric Materials ◽  
Structural Behavior ◽  
Atom Transfer ◽  
Linear Polymers ◽  
Considerable Influence

Molecular weight distribution imposes considerable influence on the properties of polymers, making it an important parameter, impacting morphology and structural behavior of polymeric materials.

Characterization of Elution Chromatography Fractions from CIS-Polybutadiene by GPC

1970 ◽  
Vol 43 (6) ◽  
pp. 1439-1450 ◽  
Author(s):  
W. V. Smith ◽  
S. Thiruvengada
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Low Molecular Weight ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Log Normal ◽  
Analytical Fractionation ◽  
Molecular Weight Fractions ◽  
Elution Chromatography

Abstract A preparative fractionation of about 23 g of a commercial cis-polybutadiene rubber is described. The method employed was a solvent elution chromatographic method with very little temperature gradient. The molecular weight distributions of the fractions obtained were determined by an analytical fractionation of 20 mg of polymer. The method was similar to the preparative fractionation and involved solvent elution chromatography. The fractions obtained were assayed for quantity, molecular weight, and molecular weight distribution by GPC. The low molecular weight fractions of the preparative fractionation had molecular weight distributions which could be closely approximated by two log normal distributions, the low molecular weight component having the narrower width. The ratio of weight to number average molecular weight was found to be about 1.1 for these samples. The higher molecular weight fractions could also be approximated by two log normal distributions; however, in these fractions the low molecular weight component had a very broad distribution but constituted only a small portion of the sample. The widths of the GPC curves of the fractions correlate satisfactorily with the molecular weight distributions found by the analytical refractionations. The GPC width is a sensitive criterion of the width of the molecular weight distribution even when only two columns are used. It is felt that the analytical fractionation procedure presented gives more detailed information on the molecular weight distribution than is easily obtainable from an ordinary GPC curve.

Study of the relationship between characteristics of aramid fibrids and mechanical property of aramid paper using DSC

e-Polymers ◽  
2014 ◽  
Vol 14 (2) ◽  
pp. 139-144 ◽  
Author(s):  
Huifang Zhao ◽  
Yinbang Zhu ◽  
Lizheng Sha
Keyword(s):  
Molecular Weight ◽  
Thermal Properties ◽  
Mechanical Strength ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
High Strength ◽  
Scanning Calorimetry ◽  
The Relationship ◽  
Different Sources

AbstractFiber classification of aramid fibrids was carried out using a Bauer-McNett fiber classifier, and the molecular weight and thermal properties of different sizes of aramid fibrids were determined with viscometry and differential scanning calorimetry (DSC), respectively. Aramid handsheets were made from different sizes of aramid fibrids and aramid short fibers, and the relationship between mechanical strength of aramid handsheets and thermal properties of aramid fibrids was examined. In addition, aramid papers from four different sources were also investigated to elucidate the relationship between their thermal properties and mechanical strength. It was found that aramid fibrids passing through 30-mesh screens and remaining on 50-mesh screens and aramid fibrids with narrower molecular weight distribution are suitable for the production of high-strength aramid papers. Lower crystallinity and wider molecular weight distribution are important contributors to the lower mechanical strength of domestic aramid paper when compared to that of Nomex paper.

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