Tens?o superficial dinamica e angulo de contato de solu??es aquosas com surfatantes em superfícies artificiais e naturais

摘要

The aim of the work was to evaluate the effect of surfactants in water solutions on dynamic surface tension and contact angle formed by the spray droplets in different surfaces: artificial (glass and aluminum oxide slides) and natural (leaves surface of three species of weeds: Euphorbia heterophylla, Ipomoea grandifolia e Brachiaria plantaginea). Were studied six surfactants formulations (AntiderivaTM; UnoTM; Pronto 3TM; Li-700TM; SupersilTM and Silwet L-77TM) in water solution using the dosage recommended by the manufacturer (0.050; 0.025; 0.100; 0.250; 0.100 and 0.100 % v v-1) and twice that dose, respectively. The dynamic surface tension and the angle formed on the surfaces of the leaves were measured by tensiometer. The contact angles of the spray droplets in two surfaces (hydrophilic and hydrophobic) were obtained by the analysis of images captured by digital camera. This study reveals that the use of surfactants affect the physical-chemical properties of water solutions. The solutions with the surfactants Silwet L-77TM and SupersilTM for both appraised dosages provided the highest reductions in the dynamic surface tension and the smallest contact angles of the droplets on artificial and natural surfaces. The organosilicones surfactants in water solutions were more efficient in the reduction of the surface tension and increase the wetting area on artificial and natural surfaces. In natural targets these properties obtained with organosilicones are dependents of surface characteristics of the vegetal species.