Simultaneous Improvement of Mechanical and Fire-Safety Properties of Polymer Composites with Phosphonate-Loaded MOF Additives

Flame-retardant (FR)
additives are commonly used to improve the
fire safety of synthetic polymers, which are widely employed in manufactured
consumer goods. Incorporation of an FR in a polymer typically leads
to deterioration of its mechanical properties. It also manifests itself
in non-negligible volatile organic compound (VOC) release, which in
turn increases environmental risks carried by both the application
and disposal of the corresponding consumer goods. Herein, we present
a hierarchical strategy for the design of composite materials, which
ensures simultaneous improvement of both mechanical and fire-safety
properties of polymers while limiting the VOC release. Our strategy
employs porous metal–organic framework (MOF) particles to provide
a multifunctional interface between the FR molecules and the polymer.
Specifically, we demonstrate that the particles of environmentally
friendly HKUST-1 MOF can be infused by a modern FRdimethyl
methylphosphonate (DMMP)and then embedded into widely used
unsaturated polyesters. The DMMP–HKUST-1 additive endows the
resulting composite material with improved processability, flame retardancy,
and mechanical properties. Single-crystal X-ray diffraction, thermogravimetric
analysis, and computational modeling of the additive suggest the complete
pore filling of HKUST-1 with DMMP molecules being bound to the open
metal sites of the MOF.