Influencing Pseudoplastic Hydrogel by an Addition of Pilocarpinium Chloride

Overview

Colloidal aqueous dispersions of 2 to 5 % (weight) of hydroxypropylmethylcellulose (HMPC 4000)yield pseudoplastic mucilages and gels. Rotational viscosimetry in the cone-plate arrangementenables rapid and reproducible evaluation of the transitional region between pseudoplastic andplastic deformation, characterized by Herschel-Bulkley equation. To the traditional Ostwald’stwo-parameter relationship it adds a third one, revealing a deviation from the beginning of thecoordinates of the rheogram caused by the limiting yield stress. The obtained equations make itpossible not only to estimate apparent and real viscosity, but also the area under the curve of thepseudoplastic rheogram. The actual precondition of integration, however, is the estimation of thelimiting yield stress as the shear rate for the zero shear stress. Experimental estimation of thebottom margin for the integration of the area under the curve makes mutual comparability ofrheograms possible. At a temperature of 32 °C, analysis of variance demonstrated a significantdiminution of this area in the presence of about 2% of pilocarpinium chloride.

Key words:
rotational viscosimetry – mucilages and gels – pseudoplastic properties –rheogramme equation – pilocarpinium chloride