Gel Permeation Chromatography of Natural Rubber

1972 ◽  
Vol 45 (1) ◽  
pp. 346-358 ◽  
Author(s):  
A. Subramaniam
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Weight Distribution ◽  
Hevea Brasiliensis ◽  
Distribution Curve ◽  
Gel Permeation Chromatography ◽  
Bimodal Distribution ◽  
Fractional Precipitation ◽  
Molecular Weights ◽  
Gel Permeation

Abstract The Waters Model 200 Gel Permeation Chromatograph has been used to study the molecular weight distribution of natural rubber. The cumulative weight distribution curve of synthetic cis-polyisoprene from the GPC method showed fair agreement with the distribution obtained by fractional precipitation. For natural rubber the agreement was not so good. Natural rubber samples from six clones of Hevea Brasiliensis were examined with the GPC. Differences were observed in their distributions. Five clones showed a distinct bimodal distribution. The weight and number average molecular weights from the GPC were found to be too low. Some possible reasons for this have been suggested.

The Structure of Neoprene. I. The Molecular-Weight Distribution of Neoprene Type GN

1949 ◽  
Vol 22 (3) ◽  
pp. 680-689
Author(s):  
W. E. Mochel ◽  
J. B. Nichols ◽  
C. J. Mighton
Keyword(s):  
Molecular Weight ◽  
Natural Rubber ◽  
Osmotic Pressure ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Distribution Curve ◽  
Pressure Measurements ◽  
Dilute Solution ◽  
Molecular Weights ◽  
Good Agreement

Abstract Polychloroprene rubber (Neoprene Type GN) was fractionated by partial precipitation from dilute solution in benzene and the fractions were examined both osmotically and viscometrically in benzene solutions. The molecular-weight distribution curve for Neoprene Type GN based on osmotic pressure measurements shows a pronounced maximum at 100,000, but has a long extension to molecular weights of over one million, indicating the presence of branched or cross-linked material which is still soluble. The uniformity is somewhat less than that of sol natural rubber, while in shape the Neoprene distribution curve resembles more closely that of peptized natural rubber than fresh sol rubber. Observed variations in the slopes of the π/c vs. c and the ηsp/c vs. c curves also indicate the presence in solution of complex, branched and (or) cross-linked molecules. Calibration of the intrinsic viscosity-molecular weight relationship by osmotic pressure measurements gave good agreement with the equation: [η]=KMa, where K=1.46×10−4 and a=0.73.

Molecular Weight Distributions of Elastomers—Comparison of Gel Permeation Chromatography with Other Techniques

1965 ◽  
Vol 38 (4) ◽  
pp. 823-831 ◽  
Author(s):  
Leon W. Gamble ◽  
Lowell Westerman ◽  
Ebnest A. Knipp
Keyword(s):  
Molecular Weight ◽  
Molecular Weight Distribution ◽  
Weight Distribution ◽  
Gel Permeation Chromatography ◽  
Molecular Weights ◽  
The Past ◽  
Molecular Weight Distributions ◽  
Weight Distributions ◽  
Gel Permeation ◽  
Polymer Fractionation

Abstract During the past decade interest in polymer fractionation for evaluating molecular weight distribution has increased. New polymers, such as polypropylene, high density polyethylene and many others have been subjected to extensive characterization, but some older polymers, including natural rubber have not. In recent years column fractionation has received a great deal of attention; a review has been made by Schneider. Most of the techniques of polymer fractionation, such as precipitation from solution and column fractionation, are quite lengthy and require days or even weeks to complete. A more rapid method for molecular weight distribution has been the goal of polymer chemists for years. The most promising of the rapid methods are turbidimetric and gel permeation chromatography by which analysis is accomplished in a few hours. This paper discusses application of gel permeation chromatography to fractionation of elastomers. In addition this technique is compared with data from column fractionation, light scattering and osmometry. Some of the assumed factors used in converting gel permeation data into molecular weights are in error. But by calibration of the gel permeation chromatograph with classical methods reliable data can be obtained.

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