Correlating chemical structure and physical properties of vegetable oil esters

The influence of FA ester chemical structures on the rheology and crystallization temperature of those compounds was evaluated using methyl, n-butyl, n-octyl, and 2-ethyl-1-hexyl FA esters with different chain lengths and different degrees of unsaturation. The rheological properties were analyzed in a high-precision rheometer at various temperatures, and the crystallization temperatures were determined by DSC. Esters produced from the esterification of pure FA and from the transesterification of vegetable oils (i.e., soybean, corn, linseed, and babassu coconut oils) were evaluated. The length of the FA chain was shown to have a marked influence on the viscosity and crystallization temperature of the systems, whereas branching affected only the crystallization temperature to a significant extent. The viscosity and crystallization temperature of the systems were also influenced by the degree of unsaturation. One double bond was shown to increase viscosity, whereas two or three double bonds caused a decrease in the viscosity of the systems. Unsaturation lowered the crystallization temperature in all cases, regardless of the number of double bonds. From all the oils studied, methyl esters from babassu coconut oil presented the lowest crystallization temperatures.