# Advanced Phosphorus–Protein Hybrid Coatings for Fire Safety of Cotton Fabrics, Developed Through the Layer-by-Layer Assembly Technique

## TL;DR

Researchers developed an eco-friendly, bio-based flame retardant coating for cotton fabrics using a layer-by-layer method, significantly improving fire safety and reducing smoke and heat release.

## Contribution

A novel phosphorus–protein hybrid coating is introduced for sustainable fire protection of cotton fabrics.

## Key findings

- The phosphorus–protein coating forms a crosslinked network that enhances thermal stability and fire resistance.
- Flame-retarded cotton showed 25% lower peak heat release rate, 54% lower total heat release, and 72% lower total smoke production.
- The coating results in higher char residue, improving overall flame-retardant performance.

## Abstract

An advanced, eco-friendly, and fully bio-based flame retardant (FR) system has been created and applied to the cellulose structure of the cotton fabric through a layer-by-layer coating method. This study examines the flame-retardant mechanism of protein-based and phosphorus-containing coatings to improve fire resistance. During combustion, the phosphate groups (−PO₄2−) in phosphorus containing flame retardant layers interact with the amino groups (–NH2) of protein, forming ester bonds, which results in the generation of a crosslinked network between the amino groups and the phosphate groups. This structure greatly enhances the thermal stability of the residual char, hence improving fire resistance. Cone calorimeter and flammability tests show significant improvements in fire safety, including lower peak heat release rates, reduced smoke production, and higher char residue, all contributing to better flame-retardant performance. pHRR, THR, and TSP of the flame-retarded cotton fabric demonstrated 25, 54, and 72% reduction, respectively. These findings suggest that LbL-assembled protein–phosphorus-based coatings provide a promising, sustainable solution for creating efficient flame-retardant materials.