Characterization of fatty acid methyl esters by thermal analysis

The thermal stability of selected straight-chain (C₆-C₁₄) esters of fatty acids has been studied by TG-DTG and DTA analysis. In DTG, a peak is detected between 84° and 125° C followed by a main effect in the range 105°–215°C, whereas in DTA only an exothermic peak appears in the range of 126.5° to 187°C (onset temperatures). The temperatures of these effects have been related with ignition points, molecular weights and boiling points. The characteristics of melting and recrystallization of the above fatty acid methyl esters and those with carbon numbers between C₁₄ and C₂₄ have been established by DSC along the melting range between ?83° and 50°C. Polymorphism appears in caproic, heptanoic, palmitic and stearic acid methyl esters.