Uniformly-Dispersed Black Phosphorene as Flame-Retardant Epoxy Composites via Iterative Dispersion Strategy

Black phosphorus (BP) nanosheets
are widely used in flame
retardant
polymers, but the challenge of poor dispersion in polymers increases
their additions and raises the cost of BP-based flame-retardant materials.
Here, we propose an iterative dispersion strategy that gradually approaches
a homogeneous dispersion state by separating aggregates and dispersions
in the BP partial dispersion with multiple cycles. An iron(III) trifluoromethanesulfonate
functionalized BP (BFF) is utilized for the flame retardant and reinforcing
modification of the epoxy matrix to verify the reliability of this
strategy, noting that the F element in BFF can achieve dynamic hydrogen
bonds with the epoxy-amine system during the curing process, further
promoting dispersion. Therefore, epoxy thermosets with only 0.2 wt
% BFF loading achieve UL-94 V-0 level with a limiting oxygen index
(LOI) of 29.2% through the synergistic effect of iterative dispersion
and dynamic hydrogen bond. The formation of hydrogen bonds between
BFF and the epoxy matrix also contributes to a significant increase
in the mechanical properties. This work provides a reasonable and
facile concept to achieve sufficient dispersion of inorganic nanosheets
in polymer or organic matrices and also promotes the process of industrial
large-scale manufacturing of BP-based fire-retardant materials.