Ultrafine nickel nanocatalyst-engineering of an organic layered double hydroxide towards a super-efficient fire-safe epoxy resin via interfacial catalysis

Abstract

Aiming to impart epoxy resin (EP) with super-efficient fire safety, organically modified layered double hydroxide (LDH-DBS) nanosheets were surface-assembled by an ultrafine Ni(OH)₂ nanocatalyst via circular coordination-induced growth. LDH-DBS@Ni(OH)₂ was designed to exploit a spatial-dependent catalytic strategy to strengthen the interfacial structure between the LDH nanosheets and the EP matrix during a dynamic charring process. Adaquate characterization verified the successful preparation of LDH-DBS@Ni(OH)₂, with Ni(OH)₂ nanocrystals uniformly distributed on the LDH nanosheets. LDH-DBS@Ni(OH)₂ presented better nano-dispersion in an EP matrix relative to LDH-DBS. The results illustrate that a mere 3 wt% of LDH-DBS@Ni(OH)₂ imparted the EP matrix with a value of UL-94 V-0. The peak heat release rate and total smoke production at 200 s were reduced by 60.6% and 66.5%, respectively, upon the addition of 3 wt% LDH-DBS@Ni(OH)₂, accompanied by tremendously suppressed CO production. In parallel, the thermal degradation analysis revealed that the interfacial growth of the Ni(OH)₂ nanocatalyst resulted in a significant reduction in volatiles, including CO, and aliphatic and aromatic compounds. A further investigation of the mechanism by dynamic charring analysis revealed the remarkable contribution of interfacial-charring catalysis to the reinforcement of the intumescent char structure and fire safety. In perspective, the interfacial-catalytic assembly of nanomaterials without traditional fire-retardant elements opens up a novel window and scale-up prospects for the production of polymers with super-efficient fire safety properties.