STUDY OF ACIDIC HYDROLYSIS OF SLES AND ITS IMPACT ON PHASE BEHAVIOUR

Abstract

Sodium Lauryl ether sulfates (SLES) are widely used anionic surfactants in liquid detergents. The understanding of hydrolysis of SLES under acidic conditions during manufacture and storage is critical in formulating antimicrobial liquid products at lower pH. In this work degradation kinetics of SLES has been studied under various conditions. The effect of ethoxylation and other typical formulation ingredients in a detergent liquid like electrolytes, hydrotope and organic acids on the kinetics of hydrolysis was examined. In addition changes in interfacial properties and phase behavior of SLES due to degradation also been investigated. Rate constant of hydrolysis under various study conditions have been determined. Rate of hydrolysis of SLES found to be increase with increase in number of ethoxyl groups. Presence of buffers, low molecular weight organic acids like citric acid and electrolytes were found to reduce the kinetics of hydrolysis. No significant influence of the hydrotope was observed on the degradation kinetics .As a result of hydrolysis SLES showed a phase change from isotropic solution to lamellar phase. Surface occupation of degradation products of SLES such as dodecanol or dodeyl ethers leads to lowering of surface tension of SLES solutions.