Development of Flame-Resistant Cotton Fabrics with Casein Using Pad-dry-cure and Supercritical Fluids Methods

Traditional pad-dry-cure (PDC) and supercritical carbon dioxide (scCO2) methods were used to study the effectiveness of cotton fabrics treated with casein from bovine milk and eco-friendly inorganic materials, urea and diammonium phosphate. Trials were completed successfully. Thermogravimetric analysis (TGA), microscale combustion calorimeter (MCC), 45° angle and vertical flammability (clothing textiles test) and limiting oxygen index (LOI) tests were carried out for the treated cotton fabrics. When the treated fabrics were tested using the 45° angle flame, the ignited fabrics self-extinguished and left behind a streak of char. Treated higher add-on fabrics were neither consumed by flame, nor produced glowing embers upon self-extinguishing. All untreated cotton fabrics showed limiting oxygen index (LOI) values of about 18% oxygen in nitrogen. For formulations with casein, urea and diammonium phosphate, LOI values of treated fabrics were 29-40% oxygen in nitrogen when add-on values for the formulation were 9.5-18.7wt%. Furthermore, scanning electron microscope (SEM) was employed to characterize the chemical structure on the treated fabrics, as well as, the surface morphology of char areas of treated and untreated fabrics. The results indicate that fabrics treated with casein are flame resistant. The treated fabrics exhibited improved thermal stability, as evidenced by increased ignition times and lower heat release rates. The results of this study show that casein coated flame-resistant fabrics can be readily applied to textile fabrics using a continuous process that is ideal for commercial and industrial applications.