TONY O’LENICK
SurfaTech Corporation, Lawrenceville, Ga, USA

Abstract

There is a growing interest in the personal care market to (1) replace synthetic oils like mineral oil and silicone fluids and (2) to modify skin aesthetics using naturally derived esters as emollients. Esters and polyesters are finding increasing usage in this application. Blends of different esters and polyesters also provide what have been referred to as cascade ester combinations. Liquid esters that are branched and provide a dry feel with minimal cushion in formulations, commonly are derived from synthetic sources. This article will review some ester structures that effect melting point, a key easily measured property that relates to both cushion and play time. The ability to modify melting point, polarity, and alkyl chain length will allow the formulator to improve their formulations. This article is one in a series of articles that will show the different properties of esters and polyesters when properly selected. This is the first in the series and will look at melting point of many simple esters. A subsequent article will cover polyesters and blends of polyesters and simple esters used to optimize performance.

Esterification Reaction
Esters are becoming more and more popular in cosmetic formulations. Properly selected, esters that are either natural or naturally derived can impact positively and significantly in formulation, replacing dimethicone, mineral oil and other less sustainable oils. Properly selected esters can improve aesthetics and offer heretofore unavailable properties.
Esters are a class of compounds that have been used as polar oils in many formulations. Esters consist of a carbonyl group (C=O) covalently bonded to –OR, where R is an alkyl group. Esters cover a wide range of products and are classified by the groups connected on either side of the -C(O)O- bond. The majority of esters used in the cosmetic field are produced by the so called “direct Esterification” process”. Direct esterification is a process by which organic acid and an alcohol are directly reacted. This distinguishes them form “trans-esterification esters”, which as the name suggests are made by trans-esterification. Trans-esterification is a process of reacting alcohol with an ester, rather than an acid. A simple example is reacting methyl stearate with deca ...