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

Qi, Xiao-Lin, Zhou, Dong-Dong, Zhang, Jing, Hu, Shuang, Haranczyk, Maciej, Wang, De-Yi
ACS applied materials & interfaces 2019 v.11 no.22 pp. 20325-20332
X-ray diffraction, additives, composite materials, coordination compounds, fire safety, flame retardants, mechanical properties, models, polyesters, risk, thermogravimetry, volatile organic compounds
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.