Ultrasonic modification of the viscosity of vegetable, mineral and synthetic oils — effects of nucleating agents and free‐radical scavengers

We describe the ultrasonic initiated modification of four types of oil; sunflower oil, transformer oil, cable oil and silicone oil. Ultrasound is effective in initiating and driving reactions of the three hydrocarbon oils but ineffective in the case of silicone oil. The hydrocarbon oils showed noticeable reductions in viscosity after sonication; this reduction can be enhanced by incorporating nucleating agents such as particulate carbon. The viscosity loss is not permanent without using stabilisers and with time the viscosity approaches its initial value. The ultrasonic reaction is thought to be free radical in nature, since incorporation of a radical scavenger before sonication prevents any viscosity loss, whereas incorporation after sonication stabilises the drop in viscosity. Oxygen is proposed to be involved since purging with nitrogen diminishes any viscosity drop observed, and selected ion flow tube MS analysis of volatiles from the oils after sonication indicates an increase in the number and quantity of oxidised products.