The Impact of Color Dyes used in Textile Face Masks on the Physicochemical Properties of the Fabric Surface and their Influence on the Biocontamination Risk

During the COVID-19 pandemic, colored cloth masks became popular for their attractive designs and reusability. However, the effect of dyeing on the masks’ fabric properties and microorganism adhesion remains largely unexplored. This study investigates how mask coloration influences the adhesive behavior of bacterial and viral strains on colored cloth mask.

Four masks (white, light blue, dark blue, and grey), composed of two textile layers, were analyzed. The surface properties were assessed using contact angle measurements, while the morphological structure was evaluated using Scanning Electron Microscopy (SEM). The biocontamination risk was studied   with a thermodynamic approach using three bacterial strains (Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa (P. aeruginosa), and Escherichia coli (E. coli)) and three viruses (HDV5, HSRV, and MS2).

The results indicated that the internal surface, which is the same across all masks, exhibited hydrophobic properties with a water contact angle of 118.8° and a surface free energy (∆Giwi) of − 60.5 mJ/m². The electron acceptor character was 5.5 mJ/m². while the electron donor character was 0.1 mJ/m².

The outer layer of the white mask was hydrophilic (θwater = 22°) with a surface free energy (∆Giwi) of 38.47 mJ/m², while the other masks were hydrophobic, with contact angles ranging from 101° to 110.3° and a surface free energy ranging from − 45.18 mJ/m² to − 78.5 mJ/m². The electron donor character was higher for the white mask compared to the other colors, while the electron acceptor character remained consistent across all masks.

Predictive adhesion, measured by total free energy (ΔG^tot), indicated that adhesion was generally unfavorable on the white mask and more favorable on the dark blue mask. The color effect is most noticeable in E. coli adhesion and the two respiratory viruses (HADV5 and HRSV). Risk analysis classified the biocontamination risk in descending order as: dark blue > grey > light blue > white mask.