Dynamic Surface Tension of Dilute Aqueous Solutions of Nonionic Cellulose Derivatives in Relation to Other Macromolecular Characterization Parameters
✍ Scribed by Bengt Persson; Stefan Nilsson; Rolf Bergman
- Publisher
- Elsevier Science
- Year
- 1999
- Tongue
- English
- Weight
- 98 KB
- Volume
- 218
- Category
- Article
- ISSN
- 0021-9797
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✦ Synopsis
The dynamic surface tension of 10 nonionic water soluble cellulose derivatives with molecular weights (M w ) in the range 100,000 -1,300,000 has been measured by the pendant drop method at the water/air interface. The surface tension measured after 11.7 h, ␥*, was taken as an apparent steady state surface tension. The ␥* at the highest concentration, 500 ppm, ␥* 500 , showed values from 63 to 37 mN/m, and the value of ␥* 500 depends on the hydrophilic/hydrophobic balance of the polymer. The aim of the present work was to discuss the dynamic surface tension in relation to some other characterization parameters, like M w , diffusion coefficient, intrinsic viscosity ([]), cloud point, and degree of hydrophilic/hydrophobic substitution. Dynamic surface tension was shown in a concentration range of 2-10 ppm. The time to reach (␥ H2O -␥*)/2, defined as t 1/2 , was found to be inversely correlated both to the diffusion coefficient and to the square of the bulk concentration, which can be expected for a diffusion controlled process. The time t 1/2 showed an approximately linear relationship against [] 1/3 . The pendant drop was found to decrease in volume with time due to the high vapor pressure caused by the curvature of the drop (⌬P ؍ 2␥/r drop ).