MOF Flame Retardant

Metal-organic framework (MOF)-derived flame retardants have recently emerged as a new class of additives in polymeric materials. Alfa Chemistry is committed to the continuous innovation and development of flame retardants (FRs), providing MOF materials and their derivatives with flame retardant potential.

Typical Products

Typical MOFs include zeolite imidazolate frameworks (ZIFs), MILs, UiOs, etc.

Advantages

Compared with traditional FRs, MOF FRs have fascinating characteristics in the following three aspects:

• Custom chemical composition
• Tunable nanostructures
• Abundant porosity

Flame Retardant Mechanism

The FR mechanism of MOF mainly involves below three functions:

• Gas and smoke absorption

After thermal decomposition, MOFs produce metal oxides that coat the surface of the polymer matrix.This layer acts as a physical barrier, protecting the associated polymer from further combustion, and effectively adsorbing gases and fumes.

• Gas dilution

MOF particles release some non-flammable gases (such as NH3), thereby diluting the concentration of flammable gases.

• Char formation

Promotes the formation of expanded carbonaceous chars or coatings that limit exposure of the bulk polymer to air, thus to reduce heat release and smoke formation.

The mechanism of ZIF-8 forming carbon [2]

Applications

• The flame retardancy potential of MOF materials is still in the research stage. MOF materials have unique structural features and tunable chemical compositions. There are many researches applying them to various polymers, such as polystyrene (PS), polypropylene (PP), epoxy resin (EP), rigid Polyurethane foam (RPUF), flexible polyurethane foam (FPUF), polycarbonate (PC), polylactic acid (PLA), thermoplastic polyurethane (TPU) and cellulose, etc.
• MOFs can be used as synergists to synergize flame retardancy with other FRs, such as ammonium polyphosphate, expandable graphite, melamine cyanurate, etc.
• MOFs can be used as templates to prepare their derivative flame retardants, such as ZIF-8 and ZIF-67 as templates.

Research Information

MOF derivative flame retardant

Xia Zhou et al. designed and synthesized 3D NiCo-LDH@PZS hollow dodecahedral structures using ZIF-67 as precursor and in situ sacrificial template, and amino-containing polyphosphazene (PZS) as interfacial compatibilizer and flame retardant. In this work, due to the catalytic action coefficient effect of NiCo-LDH and the free radical trapping effect in the gas phase of PZS, the pyrolytic volatiles such as hydrocarbons and carbon oxides formed during the combustion process of the EP composites are transformed from the gas phase to the condensed state, which can effectively It impedes the exchange of thermal energy and fuel between the interior of the material and the external environment. [3]

Schematic diagram of the synthesis of NiCo-LDH@PZS [3]

References

1. Ye-Tang Pan, et al. (2020). "The rise of MOFs and their derivatives for flame retardant polymeric materials: A critical review," Composites Part B: Engineering 199, 108265.
2. Hafezeh Nabipour, et al. (2020). "Metal-organic frameworks for flame retardant polymers application: A critical review," Composites Part A: Applied Science and Manufacturing 139, 106113.
3. Xia Zhou, et al. (2019). "Design of Hierarchical NiCo-LDH@PZS Hollow Dodecahedron Architecture and Application in High-Performance Epoxy Resin with Excellent Fire Safety," ACS Appl. Mater. Interfaces11(44), 41736-41749.