Preparation of highly efficient chitosan-based flame retardant coatings with good antibacterial properties for cotton fabrics

Improving the flame retardancy, thermal stability and antibacterial properties of cotton fabric are necessary for using it safely. To achieve this goal, melamine phosphate (MP) was added to nanochitosan (nCH) and polyvinyl alcohol (PVA) solution to prepare flame retardant coatings for cotton fabric. In addition, melamine salt of chitosan phosphate (MCHP) was prepared, mixed with PVA and used as a coating for cotton fabric. Limiting oxygen index (LOI) data indicated that PVA/nCH/MP and PVA/MCHP coatings increased LOI of cotton fabric from 17.2% to 57.9% and 58.2%, respectively. Horizontal burning rate and vertical flame spread measurements manifested, that the flame did not propagate in all treated samples. SEM images of char residue after the vertical flame spread test showed the formation of an intumescent char layer on the fabric surface that protected cotton fabric from heat and flame. The antibacterial properties against both pathogenic gram-positive (S. aureus) and gram-negative (E-coli) bacteria presented that treated samples demonstrate large inhibition zone diameters (IZD) relative to the control sample. Furthermore, the flame retardant coatings enhanced the control sample thermal stability and char residue at high temperatures. The tensile strength, water wettability, air permeability and stiffness of treated samples were measured. Durability study exhibited that treated samples were able to preserve high flame retardancy properties after the washing process.