Thermal, oxidative and low temperature properties of methyl esters prepared from oils of different fatty acids composition: A comparative study

• Methyl esters of castor oil and waste cooking oil were prepared by conventional technique.
• Thermal and oxidative stability of prepared methyl esters were estimated.
• Low-temperature properties were studied using ASTM, DSC methods and were compared.

Thermo-oxidative stabilities of castor oil methyl esters (COME) and waste cooking oil methyl esters (WCOME) were estimated using thermo gravimetric analysis technique (TGA). Low temperature properties of the methyl esters were investigated using ASTM and differential scanning calorimetry (DSC) techniques and compared. Thermo-oxidative onset temperature study showed that process of WCOME decomposition initiated and completed within a temperature range inferior to COME, because of higher percentage of polyunsaturated fatty acids in WCOME (44.41%) compared to COME (6.6%). Comparison of decomposition profile at 10 and 20 °C/min revealed that with increased heating rate degradation was found to be increased. WCOME in particular showed most unfavorable cold flow properties due to the presence of long chain saturated fatty acids (18 wt%). Comparison between ASTM and DSC method showed that DSC method could be a useful technique to estimate the low temperature properties, which also consume less time and sample amount.