Novel phosphorus-free and core-shell structured ZIF-67 for simultaneously endowing epoxy resin with excellent fire safety, corrosion and UV resistance

Two novel and eco-friendly phosphorus-free ZIF-based core-shell nanomaterials were prepared and employed to enhance fire safety of epoxy resins (EPs), which interestingly possessed both anti-corrosion and UV resistance properties. ZIF-based nanomaterials were firstly constructed by growing zinc hydroxystannate (ZHS) on surface of zeolitic imidazolate framework-67 (ZIF-67) to generate core by a simple etching method (ZIF-67@ZHS), and the sol-gel technique was then used to form shells on the surfaces (ZIF-67@ZHS@TiO2 and ZIF-67@ZHS@SiO2). After incorporation of the prepared nanomaterials into the EP, the introduced TiO2 and SiO2 shells effectively weakened the negative impact on the EP matrix because of abundant metallic elements exposed by the ZIF67@ZHS core. In particular, the EP composite sample (EP/5ZIF-67@ZHS@SiO2) with the addition of 5 wt% ZIF-67@ZHS@SiO2 showed a better cone calorimeter combustion test result with a 32.0 % reduction in peak heat release rate (PHRR) compared to pure EP. Additionally, the EP composites containing 5 wt% ZIF-67@ZHS@TiO2 and ZIF-67@ZHS@SiO2 demonstrated a significant reduction in the release of toxic gases, specifically the peak CO production (COP) decreased by 17.2 % and 34.5 % relative to pure EP, respectively. Besides, both EP/5ZIF67@ZHS@TiO2 and EP/5ZIF-67@ZHS@SiO2 coatings showed an order of magnitude improvement in impedance modulus at 0.01 Hz compared to pure EP, with EP/5ZIF-67@ZHS@SiO2 exhibiting no significant decline over 15 days. In addition, all EP composites containing modified ZIF-67 showed a decrease in UV transmittance, especially the UV transmittance of EP/5ZIF-67@ZHS@TiO2 between 350 - 400 nm decreased to below 1.8 %. This preparation strategy exhibits prominent potentials in application as a multifunctional advanced epoxy composite.