Effective enhancement of intumescent flame retardant coating by coordinating manganese ions on cotton fabrics

Abstract The intumescent flame retardant coating consisting of polyethylenimine (PEI) and poly sodium phosphate has various drawbacks including poor water durability, inferior flame retardancy, and large consumption of nonrenewable raw resources. An intumescent fire retardant coating coordinating with manganese ions was designed onto the cotton fabrics surface by a layer‐by‐layer assembly method to solve these concerns. Energy dispersive spectroscopy revealed that the coating included well‐distributed manganese ions. The thermogravimetric measurement showed that after adding manganese ions into the coating, the decomposition of treated fabrics shifted towards a lower temperature and more char residues were formed due to the catalytic effect of manganese ions. Coated cotton fabrics with manganese ions yielded the most reduction in peak heat release rate and the highest rise in char residues, up to 69.1% and 34.7%, respectively, in microscale combustion calorimeter results. Limiting oxygen index (LOI) of the samples with manganese ions was the highest, up to 28.3% and the char layer was more intact and continuous after vertical combustion test. Scanning electron microscopy analyses showed that treated cotton fabrics with manganese ions had more bubbles and char residues on the fiber surface. These findings indicated that manganese ions coordination was responsible for the catalytic and synergistic effects. Furthermore, the coating containing manganese ions exhibited better water endurance owing to high‐LOI values even after rinsing. This work shows manganese ions into intumescent flame retardant coatings improves cotton fabrics flame retardancy and water resistance.