LAUSR

ABSTRACT Electrical conductivity of fuel microemulsion composed of diesel, pentanol, water, and sucrose laurate as surfactant was investigated over a wide range of water contents varying from 0 to 90 wt% and temperature varying from 10°C to 50°C. Conductivity measurements were performed on samples, the composition of which lie along the one-phase channel using a conductivity meter. Activation energy of conduction flow was evaluated. The hydrodynamic radius as a function of temperature in the aqueous phase-rich region (90 wt%) was measured using the dynamic light scattering (DLS) method. The microstructure of the microemulsion was further investigated by NMR diffusometry by which the self-diffusion coefficients for water were determined at 25°C. Electrical conductivity increases with water content up to 40 wt% and the percolation threshold was observed, and then stabilizes between 40 and 80 wt% then decreases. Percolation threshold temperature at constant composition was monitored as 36°C for water contents below 80 wt% and as 34°C for water contents above that. As predicted by the conductivity measurements, the determined self-diffusion coefficients of water confirmed the structural transition from discrete W/O droplets to bi-continuous phase and finally to O/W droplet microemulsion. GRAPHICAL ABSTRACT