Investigating the Effects of PU-Based Back-Coating with Boric Acid and Titanium Dioxide Additives on Flame Retardancy Levels and Comfort Properties of 100% Cotton Denim Fabric

This study aimed to develop a cost-effective and resource-efficient application to enhance the thermal stability, flame retardancy, self-cleaning, and antibacterial properties of cotton denim fabrics through a single-step, flexible, and simple polyurethane (PU) based back-coating method, ultimately increasing the use of denim fabrics in daily and work clothes thanks to the increased functionality. This method utilizes boric acid (H3BO3) and a binary composite of H3BO3-titanium dioxide (TiO2) as functional additives while considering comfort parameters. Limiting oxygen index (LOI) and vertical burning tests were conducted to explore the thermal stability and flame retardancy of the samples, while assessments of air permeability, water vapour permeability, thermal resistance, and thermal absorptivity were performed to investigate the comfort properties. Comparing two kinds of back-coated denim fabrics, H3BO3-TiO2 back-coated cotton fabric showed the best flame retardancy with the lowest char length (45 mm) and highest LOI (27%). The air permeability values of back-coated fabrics decreased by approximately half compared to the untreated denim fabric. Although the water vapour permeability values decreased, they were less affected by the coating. Coating application reduced thermal conductivity and thermal absorbency, resulting in more thermally resistant denim fabric. This study demonstrates the potential utility of a PU-based coating incorporating TiO2 and H3BO3 on traditional cotton denim fabrics to enhance flame resistance while minimizing any adverse effects on the overall thermal comfort of the fabric.