Rheological behaviour of fatty acid methyl esters

Rheology of fatty acid methyl esters of soyabean, used-soyabean, mustard and used-mustard oils has been examined experimentally in the temperature range of -3 to 15 degreesC. Such a low temperature is encountered in the use of these fatty esters as diesel fuels. These fatty esters were prepared in the laboratory by the transesterification of oils with methanol in the presence of sodium hydroxide as a catalyst. Brookfield Synchro-Lectric Viscometer has been used to observe the dependence of shear rate, time, temperature on the apparent viscosity of these fatty esters. Kerosine works satisfactorily as the bath fluid in the Ultra Cryostat for the desired temperature range. The fatty acid methyl esters of soyabean, used-soyabean, mustard and used-mustard oils are found to behave as Newtonian fluids above a temperature of about 5 degreesC. Below this temperature, they are expected to behave as pseudoplastic fluids. These methyl esters also exhibit a thixotropic behaviour. The decrease in the apparent viscosity of these methyl esters with increase in temperature is approximately exponential.