Cellulose from wood fibers, as a renewable bio-material can be modified in order to be used in flame-retardant composites providing an alternative to halogen based flame retardants. For this reason bleached chemical wood fibers containing mainly cellulose have been chemically modified by phosphorylation and the resulting material has been used to prepare cellulose nanofibrils (CNF). It was shown that using different reaction conditions during phosphorylation leads to different degrees of substitution (DS) of both phosphate and carboxylate groups on the fibers. The results from nuclear magnetic resonance (NMR) spectroscopy of modified fibers were used in order to define the DS of phosphate on the surface of fibrils aggregates, which suggests that a high surface DS can be achieved even at very moderate bulk DS of phosphate groups. The presence of phosphate groups in the structure of fibrils has led to great improvement in flame-retardant properties so that the nanopaper sheets prepared from the phosphorylated CNF self-extinguished during the flammability test and did not ignite during cone calorimetry. Further the phosphorylated CNF was coupled with an aminated CNF in order to create an all cellulose flame-retardant coating through layer-by-layer (LbL) technique. It was shown that the aerogels prepared from the carboxymethylated CNF dispersions displayed improved flame-retardant properties upon application of this coating leading to an all cellulose flame-retardant material.

Use of phosphorylated cellulose nanofibrils in preparation of an all cellulose flame-retardant material

251st National Meeting (2016)

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