Influence of the Molar Mass Distribution on the Elongational Behaviour of Polymer Solutions in Capillary Breakup

2005 ◽  
Vol 15 (1) ◽  
pp. 28-37 ◽  
Author(s):  
J. P. Plog ◽  
W.-M. Kulicke ◽  
C. Clasen
Keyword(s):  
Mass Distribution ◽  
Molar Mass ◽  
Relaxation Times ◽  
Size Exclusion ◽  
Molar Mass Distribution ◽  
Mean Values ◽  
Capillary Breakup ◽  
Mass Distributions ◽  
Uniaxial Elongation ◽  
Exclusion Chromatography

AbstractCommercially available, blended methylhydroxyethyl celluloses with similar weight-average molar masses but varying molar mass distributions were characterized by different techniques like steady shear flow and uniaxial elongation in capillary breakup experiments. The determined relaxation times t were then correlated with the absolute molar mass distribution acquired via SEC/MALLS/DRI (combined methods of size-exclusion-chromatography, multi angle laser light scattering and differential refractometer). In order to describe the longest relaxation time of the polymers in uniaxial elongation via integral mean values of the molar mass distribution, defined blends of polystyrene standards with varying molar mass distributions were characterized. The obtained data was scaled via different moments of the molecular weight distribution and could be correlated with the results obtained for the methylhydroxyethyl celluloses.

scholarly journals Size-exclusion chromatography of cellulose: observations on the low-molar-mass fraction

Cellulose ◽  
2020 ◽  
Vol 27 (16) ◽  
pp. 9217-9225
Author(s):  
Leena Pitkänen ◽  
Herbert Sixta
Keyword(s):  
Mass Distribution ◽  
Size Exclusion Chromatography ◽  
Mass Fraction ◽  
Molar Mass ◽  
Accurate Determination ◽  
Size Exclusion ◽  
Molar Mass Distribution ◽  
Universal Method ◽  
Exclusion Chromatography

AbstractAccurate determination of molar mass distribution for disperse cellulose samples has proved to be a challenging task. While size-exclusion chromatography coupled to multi-angle light scattering (MALS) and differential refractive index (DRI) detectors has become the most commonly used method for molar mass determination of celluloses, this technique suffers low sensitivity at the low-molar mass range. As discussed here, the universal method for accurate molar mass distribution analysis of cellulose samples not exists and thus thorough understanding on the differences of the various methodological approaches is important. In this study, the focus is in the accurate determination of the low-molar mass fraction. The results obtained by combining the two calibration strategies, MALS/DRI for polymeric region of a cellulose sample and conventional calibration for oligomeric region, was compared to the results obtained using only MALS/DRI (with extrapolation of the curve where signal-to-noise of MALS is low). For birch pulp sample, the results from the two approaches were comparable; it should be highlighted, however, that MALS/DRI slightly overestimates the molar masses at the low-molar-mass region.

Molar mass determination of lignins by size-exclusion chromatography: towards standardisation of the method

Holzforschung ◽  
2007 ◽  
Vol 61 (4) ◽  
pp. 459-468 ◽  
Author(s):  
Stéphanie Baumberger ◽  
Alfred Abaecherli ◽  
Mario Fasching ◽  
Gäoran Gellerstedt ◽  
Richard Gosselink ◽  
...  
Keyword(s):  
Mass Distribution ◽  
Size Exclusion Chromatography ◽  
Molar Mass ◽  
Size Exclusion ◽  
Molar Mass Distribution ◽  
High Molar Mass ◽  
Wide Range ◽  
Exclusion Chromatography ◽  
Technical Lignins

Abstract The reactivity and physicochemical properties of lignins are partly governed by their molar mass distribution. The development of reliable standard methods for determination of the molar mass distribution is not only relevant for designing technical lignins for specific applications, but also for monitoring and elucidating delignification and pulping processes. Size-exclusion chromatography (SEC) offers many advantages, such as wide availability, short analysis time, low sample demand, and determination of molar mass distribution over a wide range. A collaborative study has been undertaken within the “Eurolignin” European thematic network to standardise SEC analysis of technical lignins. The high-molar-mass fraction of polydisperse lignins was shown to be the main source of intra- and interlaboratory variations, depending on the gel type, elution solvent, detection mode, and calculation strategy. The reliability of two widespread systems have been tested: one based on alkali and a hydrophilic gel (e.g., TSK Toyopearl gel) and the other based on THF as solvent and polystyrene-based gels (e.g., Styragel). A set of practical recommendations has been deduced.

Degradation of unstabilised polypropylene and a propene- 1-pentene copolymer

e-Polymers ◽  
2004 ◽  
Vol 4 (1) ◽  
Author(s):  
Stefan de Goede ◽  
Robert Brüll ◽  
Harald Pasch ◽  
Niall Marshall
Keyword(s):  
Chemical Composition ◽  
Mass Distribution ◽  
Molar Mass ◽  
Degradation Process ◽  
Size Exclusion ◽  
Molar Mass Distribution ◽  
Low Molecular Weight ◽  
Composition Distribution ◽  
Chemical Composition Distribution ◽  
Exclusion Chromatography

Abstract The degradation of polypropylene (PP) and a propene-1-pentene copolymer (P2) have been monitored with regard to chemical composition, molar mass distribution and chemical composition distribution. The increase in the carbonyl index can be monitored by IR and a decrease in molar mass can be observed from size-exclusion chromatography (SEC). CRYSTAF shows that the chemical heterogeneity of the samples broadens with continuing degradation. SEC-FTIR reveals that the degraded species are mainly found in the low-molecular-weight end of the molar mass distribution. Spatial heterogeneity of the degradation process has been proven by the analysis of abrased layers. It was found that the P2 copolymer degrades at a higher rate compared to PP.

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