Polymers impact on dissolution of washing machines soluble unit doses

Low-temperature, low-water and short washing cycles are increasingly adopted by consumers as an effective way to reduce the environmental impact of washing machines. However, these conditions are critical for the proper dissolution of laundry detergent capsules, which in parallel are spreading everywhere since their ease to use and compatibility with the fast-paced life. Understanding how their dissolution occur is therefore essential to not compromise the overall cleaning performance and to avoid consumer complaints caused by pod residues left on clothes. Given the limited scientific literature on this phenomena, this work aimed to fill this knowledge gap by investigating both the role and the mechanism of cleaning polymers during dissolution. Rheology, Small-Angle X-ray Scattering, Polarized Light Microscopy, film swelling and pod dissolution in stringent conditions, were used to investigate different polymer architectures. Results showed that polymers do not significantly modify the microstructure of detergents in the absence of water, whereas they strongly dictated its behavior when water is introduced. Particularly, polymer architecture emerged as a key parameter influencing the detergent dissolution, given its positive or negative contribution to interfering with surfactant assemblies. However, the final residues obtained from the pods also highlighted that structural modification induced on the film is an important factor to consider in evaluating the dissolution performance. This thesis is the result of a collaboration between the Brussels Innovation Centre (BIC) of Procter & Gamble (Grimbergen, Belgium) and the University of Padua.