Microscopic evaluation of the effect of washing on the optical and structural properties of cotton fabrics

The results described in this Report have been obtained within the Service Contract between the FATER S.p.A. (FATER) and the Institute for Complex Systems of the National Research Council (CNR-ISC). Within the contract, FATER entrusted the CNR-ISC for the execution of Services related to "Microscopic evaluation of the effect of washing on the Optical and structural properties in cotton fabrics ", as part of the research project "Chemistry of Interaction between Cotton Cellulose and Bleach". The activity was finalized to the achievement of the following objectives:- Objective A: analysis of cotton textile samples washed by FATER by using optical spectroscopy techniques in reflectance mode in the ultraviolet (UV), visible (Vis) and near infrared (NIR) spectral regions.- Objective B: analysis of cotton textile samples washed by FATER by using photoluminescence techniques induced by radiation in the ultraviolet.- Objective C: analysis of cotton textile samples washed by FATER by using THz Time-Domain-Spectroscopy (THz-TDS).Objective A provides quantitative results on the development of oxidized groups acting as chromophores in cellulose in cotton samples. This give a direct measurement of the yellowing of samples as a function of the number of washing and washing formulation.Objective B is able to detect the fluorescence signal of the Optical Brighteners (OBs). In this way, it is possible to follow their evolution (build-up or quenching) as a function of washings and washings formulations.Objective C allows obtaining information on the modifications of the cotton cellulose fibers at the supramolecular scale. In fact, THz-TDS is strongly sensitive to the low-energy collective vibrations of hydrogen-bonded materials. Modifications of the spectra provide indication of structural degradation of cellulose fibers.