APTES modification of ZIF-67@M(OH)(OCH 3 ) for enhanced flame retardancy and mechanical properties of epoxy resins

In this work, we employed a two-step modification process to improve the properties of 2D bimetallic nanoplates M(OH)(OCH 3 ) (M = Co, Ni), which were recently proven as a promising “nano-flame retardant”. The nanoplates were in situ modified with metal-organic framework ZIF-67 first and then silanized with a coupling agent APTES. Epoxy resin (EP) nanocomposites were fabricated using the functionalized M(OH)(OCH 3 ). We investigated the performance of the nanocomposites in flame retardance and thermal stability. The results showed that 3% of APTES@ZIF-67@M(OH)(OCH 3 ) gave the EP nanocomposite the V-1 rating in UL-94 test and the highest limited oxygen index of 27.6%. Moreover, the pHRR value of EP/APTES@ZIF-67@M 3% was reduced by 20.0% and 9.6%, respectively, compared to neat EP and EP/ZIF-67@M 3%. Regarding the mechanical properties, the Tensile properties and energy storage modulus of EP nanocomposite were both improved with 3% of APTES@ZIF-67@M(OH)(OCH 3 ). The GC-MS test results revealed that the functionalized M(OH)(OCH 3 ) significantly increased the cross-linking propensity of the EP matrix upon combustion, leading to the formation of a dense char layer. This study demonstrates the great potential of M(OH)(OCH 3 ) as a highly efficient “nano-flame retardant” with tunable functionality.