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Facile two-step phosphazine-based network coating for flame retardant cotton

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There is a need for durable flame retardant treatments for cotton fabric in order to reduce the risk associated with fires. Many current industrial treatments make use of toxic halogenated organic flame retardants or utilize formaldehyde-evolving chemistry. A facile two-step process is described to coat cotton fabric based on a spontaneous crosslinking reaction between branched polyethyleneimine (PEI) and hexachlorocyclotriphosphazene (HCCP). A coating produced from solutions of 10 wt% PEI and 5 wt% HCCP endows the cotton fabric with a high limiting oxygen index (33.8%), self-extinguishing behavior in open flame testing, and an 85% reduction in peak heat release rate. This treated fabric also maintains self-extinguishing behavior after a simulated washing test. This unique combination of properties is the result of a strongly networked coating that intumesces during burning. The simplicity of this treatment and its formaldehyde-free chemistry make it a good option for replacing organo-halogen and formaldehyde-evolving treatments.

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Branched polyethyleneimine




Crosslinked polymers produced by reaction between PEI and HCCP


Limiting oxygen index


Microscale combustion calorimeter


Thermogravimetric analysis


Scanning electron microscopy


Thermogravimetry–Fourier transform infrared spectroscopy


Heat release rate

Tp :

Temperature at peak HRR


Total heat release


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The authors want to acknowledge the National Natural Science Foundation of China (Grant 21975226) and China Scholarship Council (CSC: 201808140038). The authors wish to express thanks to Miss Kai-Li Song for her assistance with limiting oxygen index (LOI) tests.

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Correspondence to Bin Zhao or Jaime C. Grunlan.

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Zhao, B., Kolibaba, T.J., Lazar, S. et al. Facile two-step phosphazine-based network coating for flame retardant cotton. Cellulose (2020).

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  • Flame retardant
  • Cotton
  • Hexachlorocyclotriphosphazene
  • Branched polyethyleneimine