Probing the textures of composite home care formulations using Large Amplitude Oscillatory Shear (LAOS)
Formulation scientists are constantly seeking techniques to advance their ability to develop products more efficiently while meeting the key criteria of a product profile. A technique termed Large Amplitude Oscillatory Shear (LAOS) provides formulators a visual tool that allows them to build formulas with desired rheological profiles. These profiles, termed Lissajous plots, serve as unique fingerprints that characterize key components of a substance’s rheological behavior under various shear rates. The trajectory of the loops in the rheogram, under varying oscillatory strain and/or shear rates, is equated in practice to functional attributes of the product as well as sensorial textural aspects of the product. In this article, we demonstrate the use of Lissajous plots for choosing the most appropriate thickening technology to build a common hard surface cleaner formulation. Also, insight is provided into the structure-property relationships of a thickening technology by speculating how a hydrophobically-modified alkali swellable emulsion (HASE) polymer modifies the microstructure of the formulation system, and how it is affected during the course of increasingly applied shear rates.
Home care products come in an assortment of product formats as exemplified in Figure 1. Whether the product is in the form of a spray for hard surface cleaning, liquid detergent for hand dish washing or laundering textiles, or cream dispersion for cleaning and polishing, rheology is a primary factor in its functionality and efficacy. In the product development process, the formulator is faced with the challenge of choosing a technology that will provide the correct viscosity during different aspects of the product's use. One tool that can be used to facilitate this process is LAOS along with analysis of the resultant graphs that are produced, termed Lissajous plots (1-3). By examining the intricate patterns of these plots, an assessment of the rheological fea