Synthesis and characterization of functional eugenol derivative based layered double hydroxide and its use as a nanoflame-retardant in epoxy resin

Aiming to develop a multi-functional flame retardant for epoxy resins, a novel bio-based eugenol derivative containing silicon and phosphorus [((1,1,3,3-tetramethyldisiloxane-1,3-diyl)bis(propane-3,1-diyl)) bis(2-methoxy-4,1-phenylene) bis(phenylphosphonochloridate), SIEPDP] was synthesized, and was further used to modify Mg-Al layered double hydroxide (SIEPDP-LDH). This modified SIEPDP-LDH was used as a novel nanoflame-retardant for bisphenol epoxy resins and compared with unmodified pristine LDH. Xray diffraction (XRD) analysis justified that intercalation of SIEPDP into LDH increased the interlayer distance to 2.95 nm. Morphological analysis (XRD and TEM) revealed that the SIEPDP-LDH was dispersed well in the epoxy matrix in a partially exfoliated manner. Results from the cone calorimeter tests showed that even a low loading of SIEPDP-LDH into epoxy resin led to a significant decrease in heat release rate and total heat release compared to unmodified LDH/epoxy composites. More interestingly, SIEPDPLDH/epoxy's UL-94 classification passed V-0 with only 8 wt% loading. Moreover, the addition of SIEPDP-LDH enabled the increase in the impact strength and modulus of the cured epoxy. These data indicated that SIEPDP-LDH could serve as not only a nanoflame retardant but a good reinforcing agent as well.