Cellulose nanocrystals polyelectrolyte complexes as flame retardant treatment for cotton fabrics

In this work, polyelectrolyte complexes (PECs) are employed as an efficient way for the deposition of functional flame retardant coatings based on cellulose nanocrystals (CNCs). To this aim, CNCs have been combined with branched polyethyleneimine (BPEI) obtaining gel-like PECs to be deposited on cotton by an easy doctor-blading approach. The morphology of the coated fabrics was investigated by scanning electron microscopy. The thermal stability was evaluated by thermogravimetric analyses while the achieved flame retardant properties were assessed by horizontal flammability tests. The deposition of the CNCs/BPEI PECs produces a homogeneous coating capable of self-extinguishing the flame with only 8 % of weight added to the fabric. Post combustion residue investigations highlighted how these CNCs/BPEI PECs can produce a swelled charred barrier consisting of polyaromatic structures embedded within an amorphous carbon. The results reported in this paper open up to a practical and industrially viable strategy for the exploitation of CNCs in the field of flame retardant coatings.