Synthesis and Characterisation of Model Lipids for the in-situ Spectroscopic Study of Textile Detergency

This research aims to mitigate the significant implications of climate change, with a focus on the 2050 Net Zero goal, specifically within the domain of textile care. To address the climate crisis, the UK government committed to a Net Zero 2050 goal, a strategy designed to eliminate the country's contribution to global warming. Net Zero means the total greenhouse emissions emitted would be removed from the atmosphere.1 A key strategy to achieve the required energy reduction for textile cleaning processes involves minimizing water consumption, reducing wash cycle temperatures, whilst maintaining or extending the lifespan of garments.
Complex organic soils (COS), composed of lipids, proteins, sugars, and metal ions, present a significant challenge in cleaning of textiles. Their residues require repeated washing, leading to increased water, and energy consumption, contributing to textile waste in landfills. The interactions of COS components with fabric surfaces are relatively unknown and presents a considerable hurdle in understanding effective soil removal. To understand their interactions on a molecular level, a library of key lipid constituents of sebum, a major component of COS, have been labelled with Raman and IR tags. The labelling enables spectroscopic study of the soils, which can be tracked and monitored during the cleaning process. These targeted lipids include fatty acids, triglycerides, wax esters, and cholesterol, which are known to play a crucial role in soil adhesion, and persistence.
This labelling has enabled study of COS components using a novel flow Attenuated Total Reflectance Fourier-Transform Infrared (ATR-FTIR) system to mimic certain washing parameters. The labelling, particularly via deuteration ensures minimal alteration to the physical properties of the model compounds, while enabling the C-D stretches of the molecular probes to be monitored, and tracked throughout a wash cycle. This allows for a better understanding of the mechanisms governing soil removal, the interactions between different soil components, and provides an in-situ analytical tool for monitoring soil removal and evaluating various formulation conditions.
Beyond natural body soils, this work investigates unusual contaminants arising from the interactions between complex personal care formulations and household cleaning agents. Specifically, the research explores the chemical stability and removal of unsaturated fatty acids and their potential epoxidation, a process suspected to contribute to the yellowing and aging of textiles. Furthermore, a systematic study identifies an unexpected ipso-dichlorination reaction between organic UV filters found in sunscreens and household bleach (sodium hypochlorite). This reaction produces an intense red chromophore on fabrics and highlights environmental concerns regarding the discharge of chlorinated by-products into wastewater systems.
This thesis aims to give a detailed understanding of the residues responsible for fabric discoloration and soil accumulation. This knowledge is crucial for designing formulation components that enable more efficient soil removal, ultimately providing a comprehensive more targeted approach to improve cleaning efficacy and reduce the textile waste that contributes to global landfill challenges. Furthermore, the flow ATR-FTIR system can be utilised as a high-throughput screening method for evaluating the performance of different detergents and cleaning formulations.