## Abstract Different extraction techniques were applied to the fractionation of isotactic polypropylene. In solvent gradient extraction experiments two different solvent/nonβsolvent systems were studied. Investigation of the fractions obtained by GPC, DSC and FTIR indicated that the fractionation
Study of polydispersity of cotton cellulose according to molecular weight
β Scribed by Usmanov, Kh. U. ;Sushkevitch, T. I.
- Publisher
- John Wiley and Sons
- Year
- 1962
- Weight
- 334 KB
- Volume
- 58
- Category
- Article
- ISSN
- 0022-3832
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β¦ Synopsis
Abstract
A study has been made of the molecular heterogeneity of cotton fiber cellulose from fibers of different age. Analysis was carried out by the precipitation fractionation (10 to 12 fractions) and turbidity titration methods. The molecular weight distribution curves show that the cotton fiber in its early development period (grown 5 days) contains mainly low molecular weight cellulose and a small quantity of high molecular weight cellulose. Therefore, the sample is to some extent polydisperse. With continued fiber development (grown 10 to 20 days), the quantity of high molecular weight cellulose increases and the polydispersity increases also. Finally, in the late development period, the polydispersity of the sample decreases, and the fibers grown 50 days and more contain mainly homogeneous cellulose of high molecular weight. The distribution curve of the youngest fiber has only one maximum. As the fiber development proceeds, the number of maxima increases to three and reduces to one maximum again as growth is carried to maturity.
π SIMILAR VOLUMES
A previously derived general equation, correlating the intrinsic viscosity of a polymer with -~'n, ~w and 2~,, is tested with experimental data. Its application for the calculation of average molecular weights is discussed. Good results have been obtained for the calculation of 2f/" z using experime