Dielectric properties of different varieties of rapeseed-mustard oil at different temperatures

Abstract

Dielectric properties of five rapeseed-mustard oil samples having different percentage of erucic acid have been studied at 100 kHz, 8.93GHz and optical frequency of sodium light. The dielectric constant at optical frequency (є_∞) is almost the same for all the five samples, while the dielectric constant at 100 kHz (є₀), the dielectric constant at 8.93 GHz (є) and the loss factor (є) show dependence on erucic acid content, but no systematic variation with change in erucic acid is obtained which may be attributed to the presence of other fatty acids in these samples. Temperature variation of dielectric properties has also been investigated in the range 303 to 333 K. є₀ and є_∞ decrease regularly with increase in temperature while є′

and ″ do not show a regular variation with temperature, except for Hyola-401, which contains zero level of erucic acid. In other samples є′ and є″ show a maximum or minimum type of behaviour at about 313 K, which may be attributed to the presence of some type of molecular resonance/antiresonance at this temperature. The molar free energy 'of activation, (ΔFє) and the macroscopic relaxation time (<img src='/image/ spc_char/tow.gif' border=0>_m) have also been worked out whose temperature dependence requires consideration of other fatty acids also.