Some applications of viscometry from studies on the absorption of vegetable oils and solvents by paper substrates

Abstract

In previous studies on the drying performance of oleoresinous and solvent-based offset lithographic printing inks, a test was devised to determine the rate of absorption of drops of vegetable oils and solvents deposited on the surface of a paper substrate. The influence of viscosity on the rate of horizontal capillary absorption indicated a potential use of the absorption data to predict viscosity in the oxidative polymerization of polyunsaturated vegetable oils. Volumes as low as 1.0 mL could be used in thermal oxidative polymerization studies and tested by the Drop Deposition method. The stain radii Rs of absorbed drops of the oil, e.g., on blotting paper or filter paper substrates, follow a linear relationship with the square root of time ( \( {\sqrt t } \) s) and the slopes m of the Rs vs \( {\sqrt t } \) graphs are converted to dynamic viscosity in dPa.s units using a modified form of the Lucas Washburn equation from which \( m \propto {\sqrt {1 \mathord{\left/ {\vphantom {1 {2\eta }}} \right. \kern-\nulldelimiterspace} {2\eta }} } \). The study has implications for assessing the stability of vegetable oils used in frying operations. The test method may also be used in the study of room temperature oxidative polymerization of polyunsaturated vegetable oils to evaluate drier catalysts used in surface coatings.