Development of a test method to study Grease-on-Plastic cleaning through hand wash

The thesis discusses the development of a new laboratory test method at the Procter & Gamble R&D site in Brussels, Belgium. The test aims at assessing the dish soap performance in removing grease off plastic and preventing its redeposition. More specifically, the project goal is to understand the cleaning mechanism at cold temperatures. This follows the company mission of promoting sustainable cleaning practices among its consumers, through an improved cleaning performance of their products at cold temperatures. The thesis presents in detail the designed test method, which is inspired by consumers’ dishwashing techniques, and consists of suspending of a soiled plastic tile in a product solution for a defined period of time. During the cleaning process, part of the soil is removed by the soap, accounting for the removal phenomenon. However the product solution is unable to maintain in suspension the entirety of the soil droplets, therefore part of them redeposit on the soil substrate. These two phenomena are the basis for the test outputs removal and redeposition, through which dish soaps are assessed. The test method developed, after ensuring the repeatability of its results, has been used to create a ranking of products, which reflects the associated consumers’ perception. Furthermore, studying the cleaning mechanism through the test method has allowed for two significant learnings: the first one is that foam enhances the cleaning action by increasing soil removal and reducing soil redeposition; the second learning is related instead to the dependence of the cleaning performance on the type of soil and its microscopic structure.