Epoxidized esters of palm olein as plasticizers for poly(vinyl chloride)

A series of esters of palm stearin and palm olein were synthesized by alcoholysis using KOH as catalyst. Epoxidations were carried out in situ by the method of peroxyformic and peroxyacetic acids. The alcohols employed ranged from methanol to dodecyl alcohol. The esters were evaluated as plasticizers for poly(vinyl chloride) (PVC). Esters of palm stearin had poorer compatibility and might be used only as secondary plasticizers. Promising results, however, were obtained for epoxy esters of palm olein which were found to be good plasticizers for PVC. Long chain epoxy esters were less compatible while their short chain counterparts were too volatile for thermal stability. Epoxy butyl esters of palm olein were found to be most promising. The solubility parameters δ for a series of oleates, palmitates and epoxy esters were calculated using Small's method with Fredors' molar volume. Epoxystearates have higher δ values than the corresponding oleates and palmitates, in agreement with the experimental findings that epoxidation improves compatibility. Molar volumes calculated by Fredors' method were found to be in remarkable agreement with the experimental values for oleates and palmitates but were overestimated for epoxystearates. It was concluded that the palmitates were largely responsible for the poorer compatibility for the epoxy esters of palm olein prepared from higher alcohols.