The design of renewable and fully
biobased flame retardants (FRs)
with high efficiencies and mechanical reinforcement functions for
epoxy resin (EP) can greatly advance their potentials to satisfy sustainability.
Although some biobased fire retardants have been successfully developed
so far, most of existing biobased FRs are often not fully biobased
and their syntheses normally involve the use of a large volume of
organic solvents in addition to complicated synthesis processes. Herein,
we report a facile and green strategy to synthesize fully biobased
FR (P-MCC@CS@PA-Na) by surface-functionalizing microcrystalline cellulose
(MCC) with chitosan (CS) and sodium phytate (PA-Na) via layer-by-layer assembly in water. The results show that incorporating
15 wt % P-MCC@CS@PA-Na enables EP composite to pass a UL-94 V-1 rating
with a limiting oxygen index of 26.2%. Meanwhile, the peak heat release
rate, total heat release, peak smoke production release, total smoke
production, the fire growth rate, and the fire retardancy index of
the EP/15 wt % P-MCC@CS@PA-Na are greatly reduced, indicating a good
fire retardance. Notably, the well-designed P-MCC@CS@PA-Na simultaneously
strengthens and toughens the EP because of uniform dispersion and
a favorable interfacial compatibility between P-MCC@CS@PA-Na and the
EP matrix. This work provides a green strategy for the fabrication
of highly efficient multifunctional fully biobased FRs for polymers.