ANALYSIS OF DETERGENCY PROCESS BY DIFFERENTIAL SCANNING CALORIMETRY (DSC)

Abstract

The specimens of cellulose and polyester were soiled with oily substance, and then washed with aqueous surfactant solutions. The specimens after this procedure were supplied for differential scanning calorimetry (DSC). The DSC curves showed an endothermic peak due to a melting of oily substance remaining on the specimen: this peak decreased with an increase in washing time, and at the same time a broad endothermic peak appeared at temperatures between the melting peaks of oily substance and frozen water. The broad endothermic peak is supposed to be due to a ternary liquid crystal, which is formed after the contact of an aqueous surfactant solution and oily substance, and contains surfactant, water, and oily substance. The change of DSC curves with washing time suggests that the ternary liquid crystal plays an important role as an intermediate product in the process of removal of oily substance. Furthermore, it is found that DSC is a powerful method to trace an amount of residual oily substances in the detergency process.